Patent Grant
11696999
The present disclosure relates to methods and devices for treating impaired renal function across a variety of disease states and, in particular, to catheter devices, assemblies, and methods for collection of urine and/or inducement of negative pressure in the ureters and/or kidneys.
The renal or urinary system includes a pair of kidneys, each kidney being connected by a ureter to the bladder, and a urethra for draining urine produced by the kidneys from the bladder. The kidneys perform several vital functions for the human body including, for example, filtering the blood to eliminate waste in the form of urine. The kidneys also regulate electrolytes (e.g., sodium, potassium and calcium) and metabolites, blood volume, blood pressure, blood pH, fluid volume, production of red blood cells, and bone metabolism. Adequate understanding of the anatomy and physiology of the kidneys is useful for understanding the impact that altered hemodynamics other fluid overload conditions have on their function.
In normal anatomy, the two kidneys are located retroperitoneally in the abdominal cavity. The kidneys are bean-shaped encapsulated organs. Urine is formed by nephrons, the functional unit of the kidney, and then flows through a system of converging tubules called collecting ducts. The collecting ducts join together to form minor calyces, then major calyces, which ultimately join near the concave portion of the kidney (renal pelvis). A major function of the renal pelvis is to direct urine flow to the ureter. Urine flows from the renal pelvis into the ureter, a tube-like structure that carries the urine from the kidneys into the bladder. The outer layer of the kidney is called the cortex, and is a rigid fibrous encapsulation. The interior of the kidney is called the medulla. The medulla structures are arranged in pyramids.
Each kidney is made up of approximately one million nephrons. A schematic drawing of a nephron 1102 is shown in
The glomerulus is the beginning of the nephron, and is responsible for the initial filtration of blood. Afferent arterioles pass blood into the glomerular capillaries, where hydrostatic pressure pushes water and solutes into Bowman's capsule. Net filtration pressure is expressed as the hydrostatic pressure in the afferent arteriole minus the hydrostatic pressure in Bowman's space minus the osmotic pressure in the efferent arteriole.
Net Filtration Pressure=Hydrostatic Pressure (Afferent Arteriole)−Hydrostatic Pressure (Bowman's Space)−Osmotic Pressure (Efferent Arteriole) (Equation 1)
The magnitude of this net filtration pressure defined by Equation 1 determines how much ultra-filtrate is formed in Bowman's space and delivered to the tubules. The remaining blood exits the glomerulus via the efferent arteriole. Normal glomerular filtration, or delivery of ultra-filtrate into the tubules, is about 90 ml/min/1.73 m2.
The glomerulus has a three-layer filtration structure, which includes the vascular endothelium, a glomerular basement membrane, and podocytes. Normally, large proteins such as albumin and red blood cells, are not filtered into Bowman's space. However, elevated glomerular pressures and mesangial expansion create surface area changes on the basement membrane and larger fenestrations between the podocytes allowing larger proteins to pass into Bowman's space.
Ultra-filtrate collected in Bowman's space is delivered first to the proximal convoluted tubule. Re-absorption and secretion of water and solutes in the tubules is performed by a mix of active transport channels and passive pressure gradients. The proximal convoluted tubules normally reabsorb a majority of the sodium chloride and water, and nearly all glucose and amino acids that were filtered by the glomerulus. The loop of Henle has two components that are designed to concentrate wastes in the urine. The descending limb is highly water permeable and reabsorbs most of the remaining water. The ascending limb reabsorbs 25% of the remaining sodium chloride, creating a concentrated urine, for example, in terms of urea and creatinine. The distal convoluted tubule normally reabsorbs a small proportion of sodium chloride, and the osmotic gradient creates conditions for the water to follow.
Under normal conditions, there is a net filtration of approximately 14 mmHg. The impact of venous congestion can be a significant decrease in net filtration, down to approximately 4 mmHg. See Jessup M., The cardiorenal syndrome: Do we need a change of strategy or a change of tactics?, JACC 53(7):597-600, 2009 (hereinafter “Jessup”). The second filtration stage occurs at the proximal tubules. Most of the secretion and absorption from urine occurs in tubules in the medullary nephrons. Active transport of sodium from the tubule into the interstitial space initiates this process. However, the hydrostatic forces dominate the net exchange of solutes and water. Under normal circumstances, it is believed that 75% of the sodium is reabsorbed back into lymphatic or venous circulation. However, because the kidney is encapsulated, it is sensitive to changes in hydrostatic pressures from both venous and lymphatic congestion. During venous congestion the retention of sodium and water can exceed 85%, further perpetuating the renal congestion. See Verbrugge et al., The kidney in congestive heart failure: Are natriuresis, sodium, and diruetucs really the good, the bad and the ugly? European Journal of Heart Failure 2014:16, 133-42 (hereinafter “Verbrugge”).
Venous congestion can lead to a prerenal form of acute kidney injury (AKI). Prerenal AKI is due to a loss of perfusion (or loss of blood flow) through the kidney. Many clinicians focus on the lack of flow into the kidney due to shock. However, there is also evidence that a lack of blood flow out of the organ due to venous congestion can be a clinically important sustaining injury. See Damman K, Importance of venous congestion for worsening renal function in advanced decompensated heart failure, JACC 17:589-96, 2009 (hereinafter “Damman”).
Prerenal AKI occurs across a wide variety of diagnoses requiring critical care admissions. The most prominent admissions are for sepsis and Acute Decompensated Heart Failure (ADHF). Additional admissions include cardiovascular surgery, general surgery, cirrhosis, trauma, burns, and pancreatitis. While there is wide clinical variability in the presentation of these disease states, a common denominator is an elevated central venous pressure. In the case of ADHF, the elevated central venous pressure caused by heart failure leads to pulmonary edema, and, subsequently, dyspnea in turn precipitating the admission. In the case of sepsis, the elevated central venous pressure is largely a result of aggressive fluid resuscitation. Whether the primary insult was low perfusion due to hypovolemia or sodium and fluid retention, the sustaining injury is the venous congestion resulting in inadequate perfusion.
Hypertension is another widely recognized state that creates perturbations within the active and passive transport systems of the kidney(s). Hypertension directly impacts afferent arteriole pressure and results in a proportional increase in net filtration pressure within the glomerulus. The increased filtration fraction also elevates the peritubular capillary pressure, which stimulates sodium and water re-absorption. See Verbrugge.
Because the kidney is an encapsulated organ, it is sensitive to pressure changes in the medullary pyramids. The elevated renal venous pressure creates congestion that leads to a rise in the interstitial pressures. The elevated interstitial pressures exert forces upon both the glomerulus and tubules. See Verburgge. In the glomerulus, the elevated interstitial pressures directly oppose filtration. The increased pressures increase the interstitial fluid, thereby increasing the hydrostatic pressures in the interstitial fluid and peritubular capillaries in the medulla of the kidney. In both instances, hypoxia can ensue leading to cellular injury and further loss of perfusion. The net result is a further exacerbation of the sodium and water re-absorption creating a negative feedback. See Verbrugge, 133-42. Fluid overload, particularly in the abdominal cavity is associated with many diseases and conditions, including elevated intra-abdominal pressure, abdominal compartment syndrome, and acute renal failure. Fluid overload can be addressed through renal replacement therapy. See Peters, C. D., Short and Long-Term Effects of the Angiotensin II Receptor Blocker Irbesartanon Intradialytic Central Hemodynamics: A Randomized Double-Blind Placebo-Controlled One-Year Intervention Trial (the SAFIR Study), PLoS ONE (2015) 10(6): e0126882. doi:10.1371/journal.pone.0126882 (hereinafter “Peters”). However, such a clinical strategy provides no improvement in renal function for patients with the cardiorenal syndrome. See Bart B, Ultrafiltration in decompensated heart failure with cardiorenal syndrome, NEJM 2012; 367:2296-2304 (hereinafter “Bart”).
In view of such problematic effects of fluid retention, devices and methods for improving removal of urine from the urinary tract and, specifically for increasing quantity and quality of urine output from the kidneys, are needed.
According to one example, a ureteral catheter includes a drainage lumen having a proximal portion configured to be positioned in at least a portion of a patient's urethra and/or bladder and a distal portion configured to be positioned in a patient's kidney, renal pelvis, and/or in the ureter adjacent to the renal pelvis. The distal portion includes a retention portion for maintaining positioning of the distal portion of the drainage lumen. The retention portion includes a plurality of sections, each section having one or more openings on a sidewall of the retention portion for permitting fluid flow into the drainage lumen. A total area of openings of a first section of the plurality of sections is less than a total area of openings of an adjacent second section of the plurality of sections. The second section is closer to a distal end of the drainage lumen than the first section.
According to another example, a ureteral catheter includes a drainage lumen having a proximal portion configured to be positioned in at least a portion of a patient's urethra and a distal portion configured to be positioned in a patient's kidney, renal pelvis, and/or in the ureter adjacent to the renal pelvis. The distal portion includes a retention portion for maintaining positioning of the distal portion of the drainage lumen. The retention portion includes a plurality of equal length sections of the drainage lumen, each of which has one or more openings on a sidewall of the drainage lumen for permitting fluid flow into the drainage lumen. A volumetric flow rate for fluid flowing into a proximal-most section of the plurality of sections is between about 1% and 60%, preferably between about 10% and 60%, and more preferably between about 30% and 60%, of a volumetric flow rate of fluid flowing through the proximal portion of the drainage lumen, as calculated based on a mass transfer shell balance evaluation for calculating volumetric flow rates through openings of the sections when a negative pressure of −45 mmHg is applied to a proximal end of the drainage lumens.
According to another example, a ureteral catheter includes: a drainage lumen having a proximal portion configured to be positioned in at least a portion of a patient's urethra and/or bladder and a distal portion configured to be positioned in a patient's kidney, renal pelvis, and/or in the ureter adjacent to the renal pelvis. The distal portion includes a coiled retention portion for maintaining positioning of the distal portion of the drainage lumen. The coiled retention portion includes: at least a first coil having a first diameter extending about an axis of the retention portion that is at least partially coextensive with a straight or curvilinear central axis of a portion of the drainage lumen proximal to the retention portion; and a plurality of sections, each of which includes one or more openings on a sidewall of the retention portion for permitting fluid flow into the drainage lumen. Along the plurality of sections, the sidewall of the retention portion includes a radially inwardly facing side and a radially outwardly facing side. A total area of the openings on the radially inwardly facing side is greater than a total area of the openings on the radially outwardly facing side. A total area of openings of a first section of the plurality of sections is less than a total area of openings of an adjacent second section of the plurality of sections, when the second section is closer to a distal end of the drainage lumen than the first section.
According to another example, a ureteral catheter includes a drainage lumen having a proximal portion configured to be positioned in at least a portion of a patient's urethra and/or bladder and a distal portion configured to be positioned in a patient's kidney, renal pelvis, and/or in the ureter adjacent to the renal pelvis. The distal portion includes a retention portion for maintaining positioning of the distal portion of the drainage lumen. The retention portion includes a plurality of openings on a sidewall of the retention portion for permitting fluid flow into the drainage lumen. An area of an opening of the plurality of openings which is closer to a proximal end of the retention portion is less than an area of an opening of the plurality of openings which is closer to the distal end of the drainage lumen.
According to another example, a system for inducing negative pressure in a portion of a urinary tract of a patient includes at least one ureteral catheter including a drainage lumen having a proximal portion configured to be positioned in at least a portion of a patient's urethra and/or bladder and a distal portion configured to be positioned in a patient's kidney, renal pelvis, and/or in the ureter adjacent to the renal pelvis. The distal portion includes a retention portion for maintaining positioning of the distal portion of the drainage lumen. The retention portion includes a plurality of equal length sections of the drainage lumen, each of which includes one or more openings on a sidewall of the drainage lumen for permitting fluid flow into the drainage lumen. The system also includes a pump in fluid communication with the drainage lumen of the at least one ureteral catheter. The pump is configured for inducing a positive and/or a negative pressure in a portion of the urinary tract of the patient to draw fluid into the drainage lumen through the openings of the sections of the retention portion. A total area of openings of a first section of the plurality of sections is less than a total area of openings of an adjacent second section of the plurality of sections, when the second section is closer to a distal end of the drainage lumen than the first section.
Non-limiting examples, aspects or embodiments of the present invention will now be described in the following numbered clauses:
Clause 1: A ureteral catheter, comprising: a drainage lumen comprising a proximal portion configured to be positioned in at least a portion of a patient's urethra and/or bladder and a distal portion configured to be positioned in a patient's kidney, renal pelvis, and/or in the ureter adjacent to the renal pelvis, the distal portion comprising a retention portion for maintaining positioning of the distal portion of the drainage lumen, the retention portion comprising a plurality of sections, each section comprising one or more openings on a sidewall of the retention portion for permitting fluid flow into the drainage lumen, wherein a total area of openings of a first section of the plurality of sections is less than a total area of openings of an adjacent second section of the plurality of sections, the second section being closer to a distal end of the drainage lumen than the first section.
Clause 2: The ureteral catheter of clause 1, wherein the proximal portion of the drainage lumen is essentially free of or free of openings.
Clause 3: The ureteral catheter of clause 1 or clause 2, wherein the proximal portion of the drainage lumen is configured to extend outside of the patient's body.
Clause 4: The ureteral catheter of any of clauses 1 to 3, further comprising a plurality of distance markings on the sidewall of the proximal portion of the drainage lumen to indicate how far the catheter is inserted into a urinary tract of a body of the patient.
Clause 5: The ureteral catheter of clause 4, further comprising a radiopaque band on the sidewall of the drainage lumen which is adjacent to a proximal end of the retention portion for identifying a location of the retention portion using fluoroscopic imaging, the radiopaque band having a different appearance than the distance markings when viewed by fluoroscopic imaging.
Clause 6: The ureteral catheter of any of clauses 1 to 5, wherein the drainage lumen is formed, at least in part, from one or more of copper, silver, gold, nickel-titanium alloy, stainless steel, titanium, polyurethane, polyvinyl chloride, polytetrafluoroethylene (PTFE), latex, and silicone.
Clause 7: The ureteral catheter of any of clauses 1 to 6, wherein the plurality of sections of the retention portion is biased in a coiled configuration, such that the retention portion comprises: at least a first coil having a first diameter; and at least a second coil having a second diameter, the first diameter being less than the second diameter, the second coil being closer to the distal end of the drainage lumen than the first coil, and wherein, prior to insertion into a patient's urinary tract, a portion of the drainage lumen that is proximal to the retention portion defines a straight or curvilinear central axis, and wherein, when deployed, the first coil and the second coil of the retention portion extend about an axis of the retention portion that is at least partially coextensive with the straight or curvilinear central axis of the portion of the drainage lumen.
Clause 8: The ureteral catheter of clause 7, wherein a gap between the sidewall of the drainage lumen of the first coil and an adjacent sidewall of the drainage lumen of the second coil is less than 3.0 mm, preferably between about 0.25 mm and 2.5 mm, and more preferably between about 0.5 mm and 2.0 mm.
Clause 9: The ureteral catheter of clause 7 or clause 8, wherein the first coil is a half coil extending from 0 degrees to 180 degrees and is free from openings, wherein the second coil is a full coil extending from 180 degrees to 540 degrees, and wherein the first section of the plurality of sections extends between 180 and 360 degrees of the second coil and the second section extends between 360 degrees and 540 degrees of the second coil.
Clause 10: The ureteral catheter of any of clauses 7 to 9, wherein, along the plurality of sections, the sidewall of the drainage lumen comprises a radially inwardly facing side and a radially outwardly facing side, and wherein a total area of the openings on the radially inwardly facing side is greater than a total area of the openings on the radially outwardly facing side.
Clause 11: The ureteral catheter of any of clauses 7 to 10, wherein the retention portion of the drainage lumen comprises a sidewall comprising a radially inwardly facing side and a radially outwardly facing side, and wherein one or more perforations are disposed on the radially inwardly facing side, and wherein the radially outwardly facing side is essentially free of perforations.
Clause 12: The ureteral catheter of any of clauses 7 to 11, wherein a distal-most portion of the retention portion is bent inwardly relative to a curvature of a distal-most coil, such that a central axis of the distal-most portion extends from the distal end of the drainage lumen toward the axis of the retention portion.
Clause 13: The ureteral catheter of any of clauses 7 to 12, wherein the first diameter of the first coil is about 8 mm to 10 mm and the second diameter of the second coil is about 16 mm to 20 mm.
Clause 14: The ureteral catheter of any of clauses 7 to 13, wherein the retention portion further comprises a third coil extending about the axis of the retention portion, the third coil having a diameter greater than or equal to either the first diameter or the second diameter, the third coil being closer to an end of the distal portion of the drainage lumen than the second coil.
Clause 15: The ureteral catheter of any of clauses 7 to 14, wherein the drainage lumen is transitionable between an uncoiled configuration for insertion from the patient's bladder into the patient's ureter and the coiled configuration for deployment within the patient's kidney, renal pelvis, and/or in the ureter adjacent to the renal pelvis.
Clause 16: The ureteral catheter of clause 15, wherein the drainage lumen is naturally biased to the coiled configuration.
Clause 17: The ureteral catheter of any of clauses 1 to 16, wherein the sections are of equal length.
Clause 18: The ureteral catheter of any of clauses 1 to 17, wherein a volumetric flow rate for fluid which flows into a second section is at least 30% of a volumetric flow rate of fluid which flows into the openings of the first section, as calculated based on a mass transfer shell balance evaluation for calculating volumetric flow rates through openings of the sections when a negative pressure of −45 mmHg is applied to a proximal end of the drainage lumen.
Clause 19: The ureteral catheter of any of clauses 1 to 18, wherein a volumetric flow rate for fluid flowing into a proximal-most section of the plurality of sections is less than 60% of a volumetric flow rate for fluid flowing through the proximal portion of the drainage lumen, as calculated based on a mass transfer shell balance evaluation for calculating volumetric flow rates through openings of the sections when a negative pressure of −45 mmHg is applied to a proximal end of the drainage lumen.
Clause 20: The ureteral catheter of any of clauses 1 to 19, wherein a volumetric flow rate for fluid flowing into two proximal-most sections of the plurality of sections is less than 90% of a volumetric flow rate of fluid flowing through the proximal portion of the draining lumen, as calculated based on a mass transfer shell balance evaluation for calculating volumetric flow rates through openings of the sections when a negative pressure of −45 mmHg measured at an outflow port of a vacuum pump is applied to a proximal end of the drainage lumen.
Clause 21: The ureteral catheter of any of clauses 1 to 20, wherein openings of a third section of the plurality of sections have a total area that is greater than the total area of the openings of the first section or the second section, and wherein the third section is closer to the distal end of the drainage lumen than the first section or the second section.
Clause 22: The ureteral catheter of any of clauses 1 to 21, wherein a total area of the one or more openings of a section increases for sections closer to a distal end of the retention portion.
Clause 23: The ureteral catheter of any of clauses 1 to 22, wherein the drainage lumen has an inner diameter of between about 0.5 mm and 1.5 mm, and wherein a total area of openings of the first section and/or a total area of openings of the second section is between about 0.002 mm2 and about 2.5 mm2.
Clause 24: The ureteral catheter of any of clauses 1 to 23, wherein the drainage lumen has an inner diameter of between about 0.5 mm and 1.5 mm, and wherein a total area of openings of the first section is between about 0.002 mm2 and about 1.0 mm2 and a total area of openings of the second section is greater than about 0.5 mm2.
Clause 25: The ureteral catheter of clause 24, wherein each of the sections of the plurality of sections is an equal length of between about 5 mm and about 35 mm, and preferably between about 5 mm and 15 mm.
Clause 26: The ureteral catheter of any of clauses 1 to 25, wherein the drainage lumen has an uncoiled longitudinal length of between about 30 cm and about 120 cm.
Clause 27: The ureteral catheter of any of clauses 1 to 26, wherein one or more of the openings have a cross-sectional area of between about 0.002 mm2 and about 0.25 mm2, and wherein the second section comprises more openings than the first section.
Clause 28: The ureteral catheter of any of clauses 1 to 27, wherein the drainage lumen comprises an open distal end having an inner diameter of between about 0.5 mm and about 1.5 mm.
Clause 29: The ureteral catheter of any of clauses 1 to 28, wherein the openings are circles with a diameter of between about 0.5 mm and about 1.5 mm, and wherein a diameter of an opening of one of the sections is at least 0.05 mm greater than a diameter of an opening of a proximally adjacent section.
Clause 30: The ureteral catheter of any of clauses 1 to 29, wherein a distance between a center of an opening of one of the sections and a center of an opening of an adjacent section is between about 5.0 mm and about 15.0 mm.
Clause 31: The ureteral catheter of any of clauses 1 to 30, wherein the openings of the plurality of sections are circular and have a diameter of between about 0.05 mm and about 1.0 mm.
Clause 32: The ureteral catheter of any of clauses 1 to 31, wherein each section comprises a single opening.
Clause 33: The ureteral catheter of clause 32, wherein an area of a single opening of a section closer to the proximal portion of the drainage lumen is less than an area of a single opening of a section closer to the distal end of the drainage lumen.
Clause 34: The ureteral catheter of clause 32 or clause 33, wherein an area of each of the single openings is less than an area of a distally adjacent single opening.
Clause 35: The ureteral catheter of any of clauses 32 to 34, wherein the distal end of the drainage lumen has an opening having an area greater than an area of the single opening of an adjacent section of the plurality of sections.
Clause 36: The ureteral catheter of any of clauses 1 to 35, wherein each of the openings of the plurality of sections has the same area, and wherein the second section comprises more openings than the first section.
Clause 37: The ureteral catheter of any of clauses 1 to 36, wherein at least two openings of a section of the plurality of sections are arranged such that a virtual line extending around a circumference of the sidewall of the drainage lumen contacts at least a portion of each of the at least two openings.
Clause 38: The ureteral catheter of any of clauses 1 to 37, wherein the openings of at least one of the sections are arranged such that a virtual line extending along the sidewall of the drainage lumen in a curvilinear direction contacts at least a portion of each of the openings of the respective section.
Clause 39: The ureteral catheter of any of clauses 1 to 38, wherein openings of the first section are arranged along a first virtual line extending in an curvilinear direction along the sidewall of the drainage lumen, wherein at least one of the openings of the second section is arranged along a second virtual line extending in a curvilinear direction along the sidewall of the drainage lumen, and wherein at least one of the openings of the second section is arranged along a third virtual line extending in a curvilinear direction along the sidewall of the drainage lumen.
Clause 40: The ureteral catheter of clause 39, wherein the first virtual line is not coextensive with the second virtual line and/or with the third virtual line.
Clause 41: The ureteral catheter of clause 39 or clause 40, wherein the second virtual line is not coextensive with the third virtual line.
Clause 42: The ureteral catheter of any of clauses 39 to 41, wherein the first, second, and third virtual lines are parallel.
Clause 43: The ureteral catheter of any of clauses 1 to 42, wherein each opening of a plurality of openings is independently selected from one or more of circles, triangles, rectangles, ellipses, ovals, and squares.
Clause 44: A ureteral catheter, comprising: a drainage lumen comprising a proximal portion configured to be positioned in at least a portion of a patient's urethra and a distal portion configured to be positioned in a patient's kidney, renal pelvis, and/or in the ureter adjacent to the renal pelvis, the distal portion comprising a retention portion for maintaining positioning of the distal portion of the drainage lumen, the retention portion comprising a plurality of equal length sections of the drainage lumen, each of which comprises one or more openings on a sidewall of the drainage lumen for permitting fluid flow into the drainage lumen, wherein a volumetric flow rate for fluid flowing into a proximal-most section of the plurality of sections is between about 1% and 60%, preferably between about 10% and 60%, and more preferably between about 30% and 60%, of a volumetric flow rate of fluid flowing through the proximal portion of the drainage lumen, as calculated based on a mass transfer shell balance evaluation for calculating volumetric flow rates through openings of the sections when a negative pressure of −45 mmHg is applied to a proximal end of the drainage lumens.
Clause 45: The ureteral catheter of clause 44, wherein a volumetric flow rate of fluid flowing into two proximal-most sections of the plurality of sections is between about 1% and 90%, preferably between about 30% and 90%, and more preferably between about 60% and 90% of the volumetric flow rate of fluid flowing through the proximal portion of the drainage lumen, as calculated based on a mass transfer shell balance evaluation for calculating volumetric flow rates through openings of the sections when a negative pressure of −45 mmHg is applied to a proximal end of the drainage lumen.
Clause 46: The ureteral catheter of clause 44 or clause 45, wherein each section comprises a single opening, and wherein a single opening of a section closer to the proximal end of the drainage lumen is less than an area of a single opening in a section closer to a distal end of the drainage lumen.
Clause 47: The ureteral catheter of any of clauses 44 to 46, wherein a distal end of the drainage lumen has an opening having an area greater than an area of a single opening of an adjacent section of the plurality of sections.
Clause 48: The ureteral catheter of any of clauses 44 to 47, wherein each of the openings of the plurality of sections has the same area, and wherein a second section of the plurality of sections comprises more openings than the proximal-most section.
Clause 49: The ureteral catheter of any of clauses 44 to 48, wherein a shape of the openings of the plurality of sections are one or more of circles, triangles, rectangles, squares, ellipses, hourglass shapes, and random perimeter openings.
Clause 50: A ureteral catheter, comprising: a drainage lumen comprising a proximal portion configured to be positioned in at least a portion of a patient's urethra and/or bladder and a distal portion configured to be positioned in a patient's kidney, renal pelvis, and/or in the ureter adjacent to the renal pelvis, the distal portion comprising a coiled retention portion for maintaining positioning of the distal portion of the drainage lumen, the coiled retention portion comprising: at least a first coil having a first diameter extending about an axis of the retention portion that is at least partially coextensive with a straight or curvilinear central axis of a portion of the drainage lumen proximal to the retention portion; and a plurality of sections, each of which comprises one or more openings on a sidewall of the retention portion for permitting fluid flow into the drainage lumen, wherein, along the plurality of sections, the sidewall of the retention portion comprises a radially inwardly facing side and a radially outwardly facing side, and wherein a total area of the openings on the radially inwardly facing side is greater than a total area of the openings on the radially outwardly facing side, and wherein a total area of openings of a first section of the plurality of sections is less than a total area of openings of an adjacent second section of the plurality of sections, the second section being closer to a distal end of the drainage lumen than the first section.
Clause 51: The ureteral catheter of clause 50, wherein the retention portion further comprises a second coil having a second diameter, the first diameter being less than the second diameter, the second coil being closer to the distal end of the drainage lumen than the first coil.
Clause 52: The ureteral catheter of clause 51, wherein the first coil is a half coil extending from 0 degrees to 180 degrees and is free from openings, wherein the second coil is a full coil extending from 180 degrees to 540 degrees, and wherein the first section of the plurality of sections extends between 180 and 360 degrees of the second coil and the second section extends between 360 degrees and 540 degrees of the second coil.
Clause 53: The ureteral catheter of clauses 51 or clause 52, wherein the retention portion further comprises a third coil extending about the axis of the retention portion, the third coil having a diameter greater than or equal to either the first diameter or the second diameter, the third coil being closer to an end of the distal portion of the drainage lumen than the second coil.
Clause 54: A ureteral catheter, comprising: a drainage lumen comprising a proximal portion configured to be positioned in at least a portion of a patient's urethra and/or bladder and a distal portion configured to be positioned in a patient's kidney, renal pelvis, and/or in the ureter adjacent to the renal pelvis, the distal portion comprising a retention portion for maintaining positioning of the distal portion of the drainage lumen, the retention portion comprising a plurality of openings on a sidewall of the retention portion for permitting fluid flow into the drainage lumen, wherein an area of an opening of the plurality of openings which is closer to a proximal end of the retention portion is less than an area of an opening of the plurality of openings which is closer to the distal end of the drainage lumen.
Clause 55: The ureteral catheter of clause 54, wherein an area of each opening of the plurality of openings is greater than an area of a proximally adjacent opening of the plurality of openings.
Clause 56: The ureteral catheter of clause 54 or clause 55, wherein a shape of each opening is independently selected from one or more of circles, triangles, rectangles, and squares.
Clause 57: A system for inducing negative pressure in a portion of a urinary tract of a patient, the system comprising: at least one ureteral catheter comprising a drainage lumen comprising a proximal portion configured to be positioned in at least a portion of a patient's urethra and/or bladder and a distal portion configured to be positioned in a patient's kidney, renal pelvis, and/or in the ureter adjacent to the renal pelvis, the distal portion comprising a retention portion for maintaining positioning of the distal portion of the drainage lumen, the retention portion comprising a plurality of equal length sections of the drainage lumen, each of which comprises one or more openings on a sidewall of the drainage lumen for permitting fluid flow into the drainage lumen; and a pump in fluid communication with the drainage lumen of the at least one ureteral catheter, the pump being configured for inducing a positive and/or a negative pressure in a portion of the urinary tract of the patient to draw fluid into the drainage lumen through the openings of the sections of the retention portion, wherein a total area of openings of a first section of the plurality of sections is less than a total area of openings of an adjacent second section of the plurality of sections, the second section being closer to a distal end of the drainage lumen than the first section.
Clause 58: The system of clause 57, wherein the pump is configured to generate the position and/or negative pressure in a proximal end of the drainage lumen.
Clause 59: The system of clause 57 or clause 58, wherein the pump applies a negative pressure of 100 mmHg or less to a proximal end of the drainage lumen.
Clause 60: The system of clause 59, wherein the pump is configured to operate at one of three pressure levels selected by a user, the pressure levels generating a negative pressure of 15 mmHg, 30 mmHg, and 45 mmHg.
Clause 61: The system of any of clauses 57 to 60, wherein the pump is configured to alternate between generating negative pressure and generating positive pressure.
Clause 62: The system of any of clauses 57 to 61, wherein the pump is configured to alternate between providing negative pressure and equalizing pressure to atmosphere.
Clause 63: The system of any of clauses 57 to 62, further comprising: one or more sensors in fluid communication with the drainage lumen, the one or more sensors being configured to determine information comprising at least one of capacitance, analyte concentration, and temperature of urine within the drainage lumen; and a controller comprising computer readable memory including programming instructions that, when executed, cause the controller to: receive the information from the one or more sensors and adjust an operating parameter of the pump based, at least in part, on the information received from the one or more sensors to increase or decrease vacuum pressure in the drainage lumen of the at least one ureteral catheter to adjust flow of urine through the drainage lumen.
Clause 64: The system of any of clauses 57 to 63, comprising a first ureteral catheter configured to be placed in a first kidney, renal pelvis, and/or in the ureter adjacent to the renal pelvis of the patient and a second ureteral catheter configured to be placed in a second kidney, renal pelvis, and/or in the ureter adjacent to the renal pelvis of the patient, wherein the pump is configured to apply negative pressure independently to the first ureteral catheter and the second ureteral catheter such that the pressure in each catheter can be the same or different from the other catheter.
Clause 65: The system of any of clauses 57 to 64, wherein the pump has a sensitivity of 10 mmHg or less.
These and other features and characteristics of the present disclosure, as well as the methods of operation and functions of the related elements of structures and the combination of parts and economies of manufacture, will become more apparent upon consideration of the following description and the appended claims with reference to the accompanying drawings, all of which form a part of this specification, wherein like reference numerals designate corresponding parts in the various figures. It is to be expressly understood, however, that the drawings are for the purpose of illustration and description only and are not intended as a definition of the limit of the invention.
Further features and other examples and advantages will become apparent from the following detailed description made with reference to the drawings in which:
As used herein, the singular form of “a”, “an”, and “the” include plural referents unless the context clearly states otherwise.
As used herein, the terms “right”, “left”, “top”, and derivatives thereof shall relate to the invention as it is oriented in the drawing figures. The term “proximal” refers to the portion of the catheter device that is manipulated or contacted by a user and/or to a portion of an indwelling catheter nearest to the urinary tract access site. The term “distal” refers to the opposite end of the catheter device that is configured to be inserted into a patient and/or to the portion of the device that is inserted farthest into the patient's urinary tract. However, it is to be understood that the invention can assume various alternative orientations and, accordingly, such terms are not to be considered as limiting. Also, it is to be understood that the invention can assume various alternative variations and stage sequences, except where expressly specified to the contrary. It is also to be understood that the specific devices and processes illustrated in the attached drawings, and described in the following specification, are examples. Hence, specific dimensions and other physical characteristics related to the embodiments disclosed herein are not to be considered as limiting.
For the purposes of this specification, unless otherwise indicated, all numbers expressing quantities of ingredients, reaction conditions, dimensions, physical characteristics, and so forth used in the specification and claims are to be understood as being modified in all instances by the term “about.” Unless indicated to the contrary, the numerical parameters set forth in the following specification and attached claims are approximations that can vary depending upon the desired properties sought to be obtained by the present invention.
Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. Any numerical value, however, inherently contains certain errors necessarily resulting from the standard deviation found in their respective testing measurements.
Also, it should be understood that any numerical range recited herein is intended to include all sub-ranges subsumed therein. For example, a range of “1 to 10” is intended to include any and all sub-ranges between and including the recited minimum value of 1 and the recited maximum value of 10, that is, all subranges beginning with a minimum value equal to or greater than 1 and ending with a maximum value equal to or less than 10, and all subranges in between, e.g., 1 to 6.3, or 5.5 to 10, or 2.7 to 6.1.
As used herein, the terms “communication” and “communicate” refer to the receipt or transfer of one or more signals, messages, commands, or other type of data. For one unit or component to be in communication with another unit or component means that the one unit or component is able to directly or indirectly receive data from and/or transmit data to the other unit or component. This can refer to a direct or indirect connection that can be wired and/or wireless in nature. Additionally, two units or components can be in communication with each other even though the data transmitted can be modified, processed, routed, and the like, between the first and second unit or component. For example, a first unit can be in communication with a second unit even though the first unit passively receives data, and does not actively transmit data to the second unit. As another example, a first unit can be in communication with a second unit if an intermediary unit processes data from one unit and transmits processed data to the second unit. It will be appreciated that numerous other arrangements are possible.
Fluid retention and venous congestion are central problems in the progression to advanced renal disease. Excess sodium ingestion coupled with relative decreases in excretion leads to isotonic volume expansion and secondary compartment involvement. In some examples, the present invention is generally directed to devices and methods for facilitating drainage of urine or waste from the bladder, ureter, and/or kidney(s) of a patient. In some examples, the present invention is generally directed to devices and methods for inducing a negative pressure in the bladder, ureter, and/or kidney(s) of a patient. While not intending to be bound by any theory, it is believed that applying a negative pressure to the bladder, ureter, and/or kidney(s) can offset the medullary nephron tubule re-absorption of sodium and water in some situations. Offsetting re-absorption of sodium and water can increase urine production, decrease total body sodium, and improve erythrocyte production. Since the intra-medullary pressures are driven by sodium and, therefore, volume overload, the targeted removal of excess sodium enables maintenance of volume loss. Removal of volume restores medullary hemostasis. Normal urine production is 1.48-1.96 L/day (or 1-1.4 ml/min).
Fluid retention and venous congestion are also central problems in the progression of prerenal Acute Kidney Injury (AKI). Specifically, AKI can be related to loss of perfusion or blood flow through the kidney(s). Accordingly, in some examples, the present invention facilitates improved renal hemodynamics and increases urine output for the purpose of relieving or reducing venous congestion. Further, it is anticipated that treatment and/or inhibition of AKI positively impacts and/or reduces the occurrence of other conditions, for example, reduction or inhibition of worsening renal function in patients with NYHA Class III and/or Class IV heart failure. Classification of different levels of heart failure are described in The Criteria Committee of the New York Heart Association, (1994), Nomenclature and Criteria for Diagnosis of Diseases of the Heart and Great Vessels, (9th ed.), Boston: Little, Brown & Co. pp. 253-256, the disclosure of which is incorporated by reference herein in its entirety. Reduction or inhibition of episodes of AKI and/or chronically decreased perfusion may also be a treatment for Stage 4 and/or Stage 5 chronic kidney disease. Chronic kidney disease progression is described in National Kidney Foundation, K/DOQI Clinical Practice Guidelines for Chronic Kidney Disease: Evaluation, Classification and Stratification. Am. J. Kidney Dis. 39:S1-S266, 2002 (Suppl. 1), the disclosure of which is incorporated by reference herein in its entirety.
Systems for Inducing Negative Pressure
With reference to
A commercially available pump which can be adapted for use with the system 1100 is the Air Cadet Vacuum Pump from Cole-Partner Instrument Company (Model No. EW-07530-85). The pump 2000 can be connected in series to the regulator, such as the V-800 Series Miniature Precision Vacuum Regulator—⅛ NPT Ports (Model No. V-800-10-W/K), manufactured by Airtrol Components Inc. Pumps which can be adapted for use with the system 2000 are also available from Ding Hwa Co., Ltd (DHCL Group) of Dacun, Changhua, China.
In some examples, at least a portion of the pump 2000 can be positioned within the patient's urinary tract, for example within the bladder. For example, the pump 2000 can comprise a pump module and a control module coupled to the pump module, the control module being configured to direct motion of the pump module. At least one (one or more) of the pump module, the control module, or the power supply may be positioned within the patient's urinary tract. The pump module can comprise at least one pump element positioned within the fluid flow channel to draw fluid through the channel. Some examples of suitable pump assemblies, systems and methods of use are disclosed in U.S. Patent Application No. 62/550,259, entitled “Indwelling Pump for Facilitating Removal of Urine from the Urinary Tract”, filed concurrently herewith, which is incorporated by reference herein in its entirety.
The patient's urinary tract comprises the patient's right kidney 2 and left kidney 4. The kidneys 2, 4 are responsible for blood filtration and clearance of waste compounds from the body through urine. Urine produced by the right kidney 2 and the left kidney 4 is drained into a patient's bladder 10 through tubules, namely a right ureter 6 and a left ureter 8, which are connected to the kidneys at the renal pelvis 20, 21. Urine may be conducted through the ureters 6, 8 by peristalsis of the ureter walls, as well as by gravity. The ureters 6, 8 enter the bladder 10 through a ureter orifice or opening 16. The bladder 10 is a flexible and substantially hollow structure adapted to collect urine until the urine is excreted from the body. The bladder 10 is transitionable from an empty position (signified by reference line E) to a full position (signified by reference line F). Normally, when the bladder 10 reaches a substantially full state, urine is permitted to drain from the bladder 10 to a urethra 12 through a urethral sphincter or opening 18 located at a lower portion of the bladder 10. Contraction of the bladder 10 can be responsive to stresses and pressure exerted on a trigone region 14 of the bladder 10, which is the triangular region extending between the ureteral openings 16 and the urethral opening 18. The trigone region 14 is sensitive to stress and pressure, such that as the bladder 10 begins to fill, pressure on the trigone region 14 increases. When a threshold pressure on the trigone region 14 is exceeded, the bladder 10 begins to contract to expel collected urine through the urethra 12.
As shown in
System 1100 is but one example of a negative pressure system for inducing negative pressure that can be used with the ureteral catheters 1212 disclosed herein. Other systems and urine collection assemblies which can be used with catheters 1212 are shown, for example, in
Exemplary Ureteral Catheters:
Specific characteristics of exemplary ureteral catheters will now be described in detail. As shown in
The tube 1222 can be formed from a flexible and/or deformable material to facilitate advancing and/or positioning the tube 1222 in the bladder 10 and ureters 6, 8 (shown in
In some examples, the drainage lumen 1224 defined by tube 1222 comprises: a distal portion 1218 (e.g., a portion of the tube 1222 configured to be positioned in the ureter 6, 8 and renal pelvis 20, 21 (shown in
In some examples, the distal portion 1218 comprises an open distal end 1220 for drawing fluid into the drainage lumen 1224. The distal portion 1218 of the ureteral catheter 1212 further comprises a retention portion 1230 for maintaining the distal portion 1218 of the drainage lumen or tube 1222 in the ureter and/or kidney. In some examples, the retention portion comprises a plurality of radially extending coils 1280, 1282, 1284. The retention portion 1230 can be a flexible and bendable to permit positioning of the retention portion 1230 in the ureter, renal pelvis, and/or kidney. For example, the retention portion 1230 is desirably sufficiently bendable to absorb forces exerted on the catheter 1212 and to prevent such forces from being translated to the ureters. Further, if the retention portion 1230 is pulled in the proximal direction P (shown in
In some examples, the retention portion 1230 comprises perforations, drainage ports, or openings 1232 (shown in
Openings 1232 can be positioned extending along on a sidewall of the tube 1222 in any direction desired, such as longitudinal and/or axial. In some examples, spacing between the openings 1232 can range from about 1.5 mm to about 15 mm. Fluid passes through one or more of the perforations, drainage ports, or openings 1232 and into the drainage lumen 1234. Desirably, the openings 1232 are positioned so that they are not occluded by tissues of the ureters 6, 8 or kidney when negative pressure is applied to the drainage lumen 1224. For example, as described herein, openings 1234 can be positioned on interior portions of coils or other structures of the retention portion 1230 to avoid occlusion of the openings 1232. In some examples, the middle portion 1226 and proximal portion 1228 of the tube 1222 can be essentially free of or free from perforations, ports, holes or openings to avoid occlusion of openings along those portions of the tube 1222. In some examples, a portion 1226, 1228 which is essentially free from perforations or openings includes substantially fewer openings than other portions of the tube 1222. For example, a total area of openings 1232 of the distal portion 1218 may be greater than or substantially greater than a total area of openings of the proximal portion 1226 and/or the distal portion 1228 of the tube 1222.
In some examples, the openings 1232 are sized and spaced to improve fluid flow through the retention portion 1230. In particular, the present inventors have discovered that when a negative pressure is applied to the drainage lumen 1224 of the catheter 1212 a majority of fluid is drawn into the drainage lumen 1224 through proximal-most perforations or openings 1232. In order to improve flow dynamics so that fluid is also received through more distal openings and/or through the open distal end 1220 of the tube 1222, larger size or a greater number of openings can be provided toward the distal end of the retention portion 1230. For example, a total area of openings 1232 on a length of tube 1222 near a proximal end of the retention portion 1230 may be less than a total area of openings 1232 of a similar sized length of the tube 1222 located near the open distal end 1220 of the tube 1222. In particular, it may be desirable to produce a flow distribution through the drainage lumen 1224 in which less than 90%, preferably less than 70%, and, more preferably, less than 55% of fluid flow is drawn into the drainage lumen 1224 through a single opening 1232 or a small number of openings 1232 positioned near the proximal end of the retention portion 1230.
In many examples, the openings 1232 are generally a circular shape, though triangular, elliptical, square, diamond, and any other opening shapes may also be used. Further, as will be appreciated by one of ordinary skill in the art, a shape of the openings 1232 may change as the tube 1222 transitions between an uncoiled or elongated position and a coiled or deployed position. It is noted that while the shape of the openings 1232 may change (e.g., the orifices may be circular in one position and slightly elongated in the other position), the area of the openings 1232 is substantially similar in the elongated or uncoiled position compared to the deployed or coiled position.
Helical Coil Retention Portion
Referring now to
In some examples, an overall height H1 of the retention portion 1230 ranges from about 10 mm to about 30 mm and, preferably about 18±2 mm. A height H2 (shown in
The retention portion 1230 can further comprise a distal-most curved portion 1290. For example, the distal most portion 1290 of the retention portion 1230, which includes the open distal end 1220 of the tube 1222, can be bent inwardly relative to a curvature of the third coil 1284. For example, a curvilinear central axis X1 (shown in
The retention portion 1230 is capable of moving between a contracted position, in which the retention portion 1230 is straight for insertion into the patient's urinary tract, and the deployed position, in which the retention portion 1230 comprises the helical coils 1280, 1282, 1284. Generally, the tube 1222 is naturally biased toward the coiled configuration. For example, an uncoiled or substantially straight guidewire can be inserted through the retention portion 1230 to maintain the retention portion 1230 in its straight contracted position, as shown for example in
In some examples, the openings 1232 are disposed essentially only or only on a radially inwardly facing side 1286 of the coils 1280, 1282, 1284 to prevent occlusion or blockage of the openings 1232. A radially outwardly facing side 1288 of the coils 1280, 1282, 1284 may be essentially free of the openings 1232. In similar examples, a total area of openings 1232 on the inwardly facing side 1286 of the retention portion 1230 can be substantially greater than a total area of openings 1232 on the radially outwardly facing side 1288 of the retention portion 1230. Accordingly, when negative pressure is induced in the ureter and/or renal pelvis, mucosal tissue of the ureter and/or kidney may be drawn against the retention portion 1230 and may occlude some openings 1232 on the outer periphery of the retention portion 1230. However, openings 1232 located on the radially inward side 1286 of the retention portion 1230 are not appreciably occluded when such tissues contact the outer periphery of the retention portion 1230. Therefore, risk of injury to the tissues from pinching or contact with the drainage openings 1232 can be reduced or eliminated.
Hole or Opening Distribution Examples
In some examples, the first coil 1280 can be free or essentially free from openings. For example, a total area of openings on the first coil 1280 can be less than or substantially less than a total area of openings of the full coils 1282, 1284. Examples of various arrangements of holes or openings which could be used for a coiled retention portion (such as coiled retention portion 1230 shown in
An exemplary retention portion 1330 is illustrated in
In some examples, each section comprises one or more openings. In some examples, each section each comprises a single opening 1332. In other examples, the first section 1310 includes a single opening 1332 and other sections comprise multiple openings 1332. In other examples, different sections comprise one or more openings 1332, each of the opening(s) having a different shape or different total area.
In some examples, such as the retention portion 1230 shown in
In some examples, the openings 1332 can be sized such that a total area of openings of the first section 1310 is less than a total area of openings of the adjacent second section 1312. In a similar manner, if the retention portion 1330 further comprises a third section 1314, then openings of a third section 1314 can have a total area that is greater than the total area of the openings of the first section 1310 or the second section 1312. Openings of the fourth 1316, fifth 1318, and sixth 1320 sections may also have a gradually increasing total area and/or number of openings to improve fluid flow through the tube 1222.
As shown in
As described herein, openings 1332, 1334, 1336, 1338, 1340 can be positioned and sized so that a volumetric flow rate of fluid passing through the first opening 1332 more closely corresponds to a volumetric flow rate of openings of more distal sections when negative pressure is applied to the drainage lumen 1224 of the catheter 1212. As described above, if each opening were the same area, then when negative pressure is applied to the drainage lumen 1224, the volumetric flow rate of fluid passing through the proximal-most of first opening 1332 would be substantially greater than a volumetric flow rate of fluid passing through openings 1334 closer to the distal end 1220 of the retention portion 1330. While not intending to be bound by any theory, it is believed that when negative pressure is applied, the pressure differential between the interior of the drainage lumen 1224 and external to the drainage lumen 1224 is greater in the region of the proximal-most opening and decreases at each opening moving toward the distal end of the tube. For example, sizes and positions of the openings 1332, 1334, 1336, 1338, 1340 can be selected so that a volumetric flow rate for fluid which flows into openings 1334 of the second section 1312 is at least about 30% of a volumetric flow rate of fluid which flows into the opening(s) 1332 of the first section 1310. In other examples, a volumetric flow rate for fluid flowing into the proximal-most or first section 1310 is less than about 60% of a total volumetric flow rate for fluid flowing through the proximal portion of the drainage lumen 1224. In other examples, a volumetric flow rate for fluid flowing into openings 1332, 1334 of the two proximal-most sections (e.g., the first section 1310 and the second section 1312) can be less than about 90% of a volumetric flow rate of fluid flowing through the proximal portion of the drainage lumen 1224 when a negative pressure, for example a negative pressure of about −45 mmHg, is applied to the proximal end of the drainage lumen.
As will be appreciated by one of ordinary skill in the art, volumetric flow rate and distribution for a catheter or tube comprising a plurality of openings or perforations can be directly measured or calculated in a variety of different ways. As used herein, “volumetric flow rate” means actual measurement of the volumetric flow rate downstream and adjacent to each opening or using a method for “Calculated Volumetric Flow Rate” described below.
For example, actual measurement of the dispersed fluid volume over time can be used to determine the volumetric flow rate through each opening 1332, 1334, 1336, 1338, 1340. In one exemplary experimental arrangement of an ex vivo test of dispersed fluid volume, a multi-chamber vessel, such as a sleeve or box, comprising individual chambers sized to receive sections 1310, 1312, 1314, 1316, 1318, 1320 of the retention portion 1330 could be sealed around and enclose the retention portion 1330. Each opening 1332, 1334, 1336, 1338, 1340 could be sealed in one of the chambers. In this arrangement, each chamber encloses an identical volume and is filled with an equal amount of fluid, such that an initial fluid pressure within each chamber is identical. Experimental conditions may be selected to be similar to fluid collection conditions in the body. For example, a temperature of 37° C. may be used and the chambers may be filled with urine having an approximate density of 1.03 g/mL and had a coefficient of friction μ of 8.02×10-3 Pa·S (8.02×10-3 kg/s·m). Negative pressure of 100 mmHg or less can be applied to a proximal end of the catheter tube for fluid collection. In some examples, a negative pressure of −15 mmHg, −30 mmHg, or −45 mmHg is applied.
An amount of fluid volume drawn from the respective chambers into the tube 3222 through each opening 1332, 1334, 1336, 1338, 1340 could be measured to determine an amount of fluid volume drawn into each opening over time when a negative pressure is applied. For example, each chamber may be initially filled with a predetermined fluid volume of, for example, 100 mL of urine. Negative pressure can be applied by a pump for a predetermined period of time, such as 30 seconds, 1 minute, 5 minutes, or 15 minutes. After the predetermined period of time, the pump can be shut off and the fluid remaining in each chamber can be measured. A difference between the measured fluid remaining and the initial fluid amount corresponds to an amount of fluid drawn into the drainage lumen of the tube through each opening. The cumulative amount of fluid volume collected in the tube 1222 by a negative pressure pump system would be equivalent to the sum of fluid drawn into each opening 1332, 1334, 1336, 1338, 1340.
Alternatively, volumetric fluid flow rate through different openings 1332, 1334, 1336, 1338, 1340 can be calculated mathematically using equations for modeling fluid flow through a tubular body. For example, volumetric flow rate of fluid passing through openings 1332, 1334, 1336, 1338, 1340 and into the drainage lumen 1224 can be calculated based on a mass transfer shell balance evaluation, as described in detail below in connection with the Mathematical Examples and
Another exemplary retention portion 2230 with openings 2332, 2334, 2336, 2338, 2340 is illustrated in
As shown in
Another exemplary retention portion 3230 with openings 3332, 3334, 3336, 3338, 3340 is illustrated in
Another exemplary retention portion 4230 with openings 4332, 4334, 4336, 4338, 4340 is illustrated in
Calculation of Volumetric Flow Rate and Percentage of Flow Distribution
Having described various arrangements of openings for retention portions of the ureteral catheter 1212, a method for determining the Calculated Percentage of Flow Distribution and Calculated Volumetric Flow Rate through the catheter will now be described in detail. A schematic drawing of an exemplary catheter with sidewall openings showing a position of portions of the tube or drainage lumen used in the following calculations is shown in
These volumetric flow rate calculations were used to determine and model fluid flow through the retention portion 1230 of the ureter catheter 1212 shown in
For the following calculations, a tube length of 86 cm having an inner diameter of 0.97 mm and an end hole inner diameter of 0.97 mm was used. Density of urine was 1.03 g/mL and had a coefficient of friction μ of 8.02×10-3 Pa·S (8.02×10-3 kg/s·m) at 37° C. The urine volumetric flow rate passing through the catheter was 2.7 ml per minute (QTotal) as determined by experimental measurement.
Calculated Volumetric Flow Rate is determined by a volumetric mass balance equation in which a sum total of volumetric flow through all perforations or openings 1232 of the five sections of the retention portion (referred to herein as volumetric flow Q2 to Q6) and through the open distal end 1220 (referred to herein as volumetric flow Q1) equals the total volumetric flow (QTotal) exiting the proximal end of the tube 1222 at a distance of 10 cm to 60 cm away from the last proximal opening, as shown in Equation 2.
QTotal=Q1+Q2+Q3+Q4+Q5+Q6 (Equation 2)
A Modified Loss Coefficient (K′) for each of the sections is based on three types of loss coefficients within the catheter model, namely: an Inlet Loss Coefficient taking into account a pressure loss resulting at a pipe inlet (e.g., the openings and open distal end of the tube 1222); a Friction Loss Coefficient which takes into account pressure loss resulting from friction between the fluid and pipe wall; and a Flow Junction Loss Coefficient taking into account pressure loss resulting from the interaction of two flows coming together.
The Inlet Loss Coefficient is dependent on a shape of the orifice or opening. For example, a tapered or nozzle shaped orifice would increase flow rate into the drainage lumen 1224. In a similar manner, a sharp-edged orifice would have different flow properties than an orifice with less defined edges. For purposes of the following calculations, it is assumed that the openings 1232 are side orifice openings and the open distal end 1220 of the tube 1222 is a sharp-edged opening. The cross sectional area of each opening is considered constant through the tube sidewall.
The Friction Loss Coefficient approximates pressure loss resulting from friction between the fluid and the adjacent inner wall of the tube 1222. Friction loss is defined according to the following equations:
The Flow Junction Loss Coefficients are derived from loss coefficients for combining flow at a branch angle of 90 degrees. Values for the loss coefficients were obtained from Charts 13.10 and 13.11 of Miller D S, Internal Flow Systems, 1990, incorporated by reference herein. The charts use the ratio of the inlet orifice area (referred to as A1 in the charts) to the pipe cross-sectional area (referred to as A3 in the charts) and the ratio of the inlet orifice volumetric flow rate (Q1 in the charts) to the resulting combined pipe volumetric flow rate (Q3 in the charts). For example, for an area ratio of 0.6 between an area of the opening and an area of the drainage lumen, the following Flow Junction Loss Coefficients (K13 and K23) would be used.
To calculate the Total Manifold Loss Coefficient (K), it is necessary to separate the model into so-called “reference stations” and progressively work through and balance the pressure and flow distributions of the two paths (e.g., flow through the opening and flow through the drainage lumen of the tube) to reach each station starting from the distal tip to the most proximal “Station”. A graphical representation of the different stations used for this calculation is shown in
To calculate loss between Station A (the distal opening) and Station B for fluid entering through the open distal end of the tube 1222 (Path 1), the modified loss coefficient (K′) is equal to:
In a similar manner, a second path to Station B is through the opening(s) 1334 of the fifth section 1318 (shown in
The modified loss coefficients of both Path 1 and Path 2 must equate to ensure the volumetric flow rates (Q1 and Q2) reflect the balanced distribution within the manifold at Station B. The volumetric flow rates are adjusted until equal modified loss coefficients for both paths is achieved. The volumetric flow rates can be adjusted because they represent a fractional portion of a total volumetric flow rate (Q′Total), which is assumed to be unity for the purpose of this step-by-step solution. Upon equating the two modified loss coefficients, one can then proceed to equating the two paths to reach station C (the fourth section 1316 in
Loss coefficients between Station B (flow through drainage lumen in the fifth section 1318) and Station C (flow through lumen in the fourth section 1316) are calculated in a similar manner as shown by Equations 5.1 and 5.2). For example, for Path 1 (Station B to Station C), the modified loss coefficient (K′) for the opening(s) of the fourth section 1316 is defined as:
K′=Loss to Station B+Friction Loss+Flow Junction Loss (Equation 6.1)
KC′=KB′+K2-3×(Q1+Q2)2+K2-4×(Q1+Q2+Q3)2 (Equation 6.2)
For Path 2 (Station B to C), the modified loss coefficient (K′) based on the flow area of the opening(s) of the fourth section 1316 are defined as:
As with the previous stations, the modified loss coefficients of both Path 1 and Path 2 must equate to ensure the volumetric flow rates (Q1, Q2, and Q3) reflect the balanced distribution within the manifold up to Station C. Upon equating the two modified loss coefficients, one can then proceed to equating the two paths to reach Station D, Station E, and Station F. The step-by-step solution process proceeds through each station as demonstrated until calculating the modified loss coefficient for the final station, Station F in this case. The Total Loss Coefficient (K) for the manifold can then be calculated using an actual QTotal (volumetric flow rate through a proximal portion of the drainage lumen) determined through experimental measurement.
The fractional volumetric flow rates calculated through the step-by-step exercise can then be multiplied by the actual total volumetric flow rate (QTotal) to determine the flow through each opening 1232 (shown in
Examples are provided below and shown in Tables 3-5 and
Example 1 illustrates a distribution of fluid flow for a retention member tube with different sized openings, which corresponds to the embodiment of the retention member 1330 shown in
The Percentage of Flow Distribution and Calculated Volumetric Flow Rate were determined as follows.
Path to Station B Through Distal End of Tube (Path 1)
Path to Station B Through Sidewall Opening (Path 2)
Path to Station C from Station B (Path 1+Path 2)
Path to Station C Through Sidewall Opening (Path 3)
Path to Station D from Station C (Path 1+Path 2+Path 3)
Path to Station D Through Sidewall Opening (Path 4)
Path to Station E from Station D (Path 1+Path 2+Path 3+Path 4)
Path to Station E Through Sidewall Opening (Path 5)
Path to Station F from Station E (Through Paths 1-5)
Path to Station F Through Sidewall Opening (Path 6)
In order to calculate flow distribution for each “Station” or opening, the calculated K′ values were multiplied by actual total volumetric flow rate (QTotal) to determine the flow through each perforation and distal end hole. Alternatively, calculated results could be presented as a percentage of total flow or a flow distribution as shown in Table 3. As shown in Table 3 and in
As demonstrated in Example 1, by increasing hole diameter and cross-sectional area from the proximal to distal regions of the retention portion, distribution of fluid flow was more evenly distributed across the entire retention portion.
In Example 2, each opening has the same diameter and area. As shown in Table 4 and
Example 3 also illustrates flow distribution for openings having the same diameter. However, as shown in Table 5, the openings are closer together (10 mm vs. 22 mm). As shown in Table 5 and
Additional Exemplary Ureteral Catheters
As shown in
In some examples, the urine collection assembly 100 can comprise two separate ureteral catheters, such as a first catheter 112 disposed in or adjacent to the renal pelvis 20 of the right kidney 2 and a second catheter 114 disposed in or adjacent to the renal pelvis 21 of the left kidney 4. The catheters 112, 114 can be separate for their entire lengths, or can be held in proximity to one another by a clip, ring, clamp, or other type of connection mechanism (e.g., connector 150) to facilitate placement or removal of the catheters 112, 114. In some examples, catheters 112, 114 can merge or be connected together to form a single drainage lumen. In other examples, the catheters 112, 114 can be inserted through or enclosed within another catheter, tube, or sheath along portions or segments thereof to facilitate insertion and retraction of the catheters 112, 114 from the body. For example, a bladder catheter 116 can be inserted over and/or along the same guidewire as the ureteral catheters 112, 114, thereby causing the ureteral catheters 112, 114 to extend from the distal end of the bladder catheter 116.
With reference to
The tube 122 can be formed from a flexible and/or deformable material to facilitate advancing and/or positioning the tube 122 in the bladder 10 and ureters 6, 8 (shown in
In some examples, the tube 122 can comprise: a distal portion 118 (e.g., a portion of the tube 122 configured to be positioned in the ureter 6, 8 and renal pelvis 20, 21); a middle portion 126 (e.g., a portion of the tube 122 configured to extend from the distal portion through the ureteral openings 16 into the patient's bladder 10 and urethra 12); and a proximal portion 128 (e.g., a portion of the tube 122 extending from the urethra 12 to an external fluid collection container and/or pump assembly). In one preferred example, the combined length of the proximal portion 128 and the middle portion 126 of the tube 122 is about 54±2 cm. In some examples, the tube 122 terminates in another indwelling catheter and/or drainage lumen, such as in a drainage lumen of the bladder catheter 116. In that case, fluid drains from the proximal end of the ureteral catheter 112, 114 and is directed from the body through the additional indwelling catheter and/or drainage lumen.
Additional Exemplary Ureteral Retention Portions:
With continued reference to
In some examples, the retention portion 130 is integral with the tube 122. In that case, the retention portion 130 can be formed by imparting a bend or curl to the catheter body 122 that is sized and shaped to retain the catheter at a desired fluid collection location. Suitable bends or coils can include a pigtail coil, corkscrew coil, and/or helical coil. For example, the retention portion 130 can comprise one or more radially and longitudinally extending helical coils configured to contact and passively retain the catheter 112 within the ureter 6, 8 proximate to or within the renal pelvis 20, 21. In other examples, the retention portion 130 is formed from a radially flared or tapered portion of the catheter body 122. For example, the retention portion 130 can further comprise a fluid collecting portion, as shown in
The retention portion 130 can further comprise one or more perforated sections, such as drainage holes or ports 132 (shown in
Referring now to
As shown in
In some examples, multiple coils 184 can have the same inner and/or outer diameter D and height H2. In that case, the outer diameter D1 of the coils 184 may range between 10 mm and 30 mm. The height H2 between coils 184 may be about 3 mm to 10 mm.
In other examples, the retention portion 130 is configured to be inserted in the tapered portion of the renal pelvis. For example, the outer diameter D1 of the coils 184 can increase toward the distal end 120 of the tube 122, resulting in a helical structure having a tapered or partially tapered configuration. For example, the distal or maximum outer diameter D1 of the tapered helical portion ranges from about 10 mm to about 30 mm, which corresponds to the dimensions of the renal pelvis. The height H2 of the retention portion 130 ranges from about 10 mm to about 30 mm.
In some examples, the outer diameter D1 and/or height H2 of the coils 184 can vary in a regular or irregular fashion. For example, the outer diameter D1 of coils or height H2 between coils can increase or decrease by a regular amount (e.g., about 10% to about 25% between adjacent coils 184). For example, for a retention portion 130 having three coils (as shown, for example, in
The retention portion 130 can further comprise the drainage ports 132 or holes disposed on or through the sidewall of the catheter tube 122 on or adjacent to the retention portion 130 to permit urine waste to flow from the outside of the catheter tube 122 to the inside of the catheter tube 122. The position and size of the drainage ports 132 can vary depending upon the desired flow rate and configuration of the retention portion. The diameter of the drainage ports 132 can range from about 0.005 mm to about 1.0 mm. The spacing between the drainage ports 132 can range from about 0.1 mm to about 255 mm. The drainage ports 132 can be spaced in any arrangement, for example, linear or offset. In some examples, the drainage ports 132 can be non-circular, and can have a surface area of about 0.002 mm2 to 0.79 mm2 or more.
In some examples, as shown in
With reference to
As shown in
With reference to
The retention portion 130 of the ureteral catheter 112 can be made from a variety of suitable materials that are capable of transitioning from the collapsed state to the deployed state. In one example, the retention portion 130 comprises a framework of tines or elongated members formed from a temperature sensitive shape memory material, such as nitinol. In some examples, the nitinol frame can be covered with a suitable waterproof material such as silicone to form a tapered portion or funnel. In that case, fluid is permitted to flow down the inner surface 186 of the retention portion 130 and into the drainage lumen 124. In other examples, the retention portion 130 is formed from various rigid or partially rigid sheets or materials bended or molded to form a funnel-shaped retention portion as illustrated in
In some examples, the retention portion of the ureteral catheter 112 can include one or more mechanical stimulation devices 191 for providing stimulation to nerves and muscle fibers in adjacent tissues of the ureter(s) and renal pelvis. For example, the mechanical stimulation devices 191 can include linear or annular actuators embedded in or mounted adjacent to portions of the sidewall of the catheter tube 122 and configured to emit low levels of vibration. In some examples, mechanical stimulation can be provided to portions of the ureters and/or renal pelvis to supplement or modify therapeutic effects obtained by application of negative pressure. While not intending to be bound by theory, it is believed that such stimulation affects adjacent tissues by, for example, stimulating nerves and/or actuating peristaltic muscles associated with the ureter(s) and/or renal pelvis. Stimulation of nerves and activation of muscles may produce changes in pressure gradients or pressure levels in surrounding tissues and organs which may contribute to or, in some cases, enhance therapeutic benefits of negative pressure therapy.
With reference to
As shown in
With reference to
With reference to
Exemplary Urine Collection Assemblies:
Referring now to
Exemplary Bladder Catheter
The bladder catheter 116 comprises a deployable seal and/or anchor 136 for anchoring, retaining, and/or providing passive fixation for indwelling portions of the urine collection assembly 100 and, in some examples, to prevent premature and/or untended removal of assembly components during use. The anchor 136 is configured to be located adjacent to the lower wall of the patient's bladder 10 (shown in
The catheter tube 138 can comprise one or more drainage ports 142 configured to be positioned in the bladder 10 for drawing urine into the drainage lumen 140. For example, excess urine left in the patient's bladder 10 during placement of the ureteral catheters 112, 114 is expelled from the bladder 10 through the ports 142 and drainage lumen 140. In addition, any urine that is not collected by the ureteral catheters 112, 114 accumulates in the bladder 10, and can be conducted from the urinary tract through the drainage lumen 140. The drainage lumen 140 may be pressurized to a negative pressure to assist in fluid collection or may be maintained at atmospheric pressure such that fluid is collected by gravity and/or as a result of partial contraction of the bladder 10. In some examples, the ureteral catheters 112, 114 may extend from the drainage lumen 140 of the bladder catheter 116 to facilitate and/or simplify insertion and placement of the ureteral catheters 112, 114.
With specific reference to
Exemplary Bladder Anchor Structures
With specific reference to
The balloon 144 is in fluid connection with an inflation lumen 146, and is inflated by introducing fluid into the balloon 144. In a deployed state, the balloon 144 can be a substantially spherical structure mounted to and extending radially outward from the catheter tube 138 of the bladder catheter 116 and comprising a central cavity or channel for the catheter tube 138 to pass through. In some examples, the catheter tube 138 extends through the cavity defined by the balloon 144, such that the open distal end 148 of the catheter tube 138 extends distally beyond the balloon 144 and toward the center of the bladder 10 (shown in
As shown in
With reference to
As shown in
With reference again to
With reference again to
In some examples, the cage 210 further comprises a shield or cover 214 over distal portions of the cage 210 to prevent or reduce the likelihood that tissue, namely, the distal wall of the bladder, will be caught or pinched as a result of contact with the cage 210 or member 212. More specifically, as the bladder contracts, the inner distal wall of the bladder comes into contact with the distal side of the cage 210. The cover 214 prevents the tissue from being pinched or caught, may reduce patient discomfort, and protect the device during use. The cover 214 can be formed at least in part from a porous and/or permeable biocompatible material, such as a woven polymer mesh. In some examples, the cover 214 encloses all or substantially all of the cavity 242. In that case, the cover 214 defines openings suitable for receiving the ureteral catheters 112, 114. In some examples, the cover 214 covers only about the distal ⅔, about the distal half, or about the distal third portion or any amount, of the cage 210. In that case, the ureteral catheters 112, 114 pass through the uncovered portion of the cage 210.
The cage 210 and cover 214 are transitionable from a contracted position, in which the members 212 are contracted tightly together around a central portion and/or around the bladder catheter 116 to permit insertion through a catheter or sheath to the deployed position. For example, in the case of a cage 210 constructed from a shape memory material, the cage 210 can be configured to transition to the deployed position when it is warmed to a sufficient temperature, such as body temperature (e.g., 37° C.). In the deployed position, the cage 210 has a diameter D that is preferably wider than the urethral opening, such that the cage 210 provides support for the ureteral catheters 112, 114 and prevents patient motion from translating through the ureteral catheters 112, 114 to the ureters. When the assembly 200 is deployed in the urinary tract, the ureteral catheter(s) 112, 114 extend from the open distal end 248 of the bladder catheter 216, past the longitudinally extending members 212 of the cage 210, and into the bladder. Advantageously, the open (e.g., low profile) arrangement of the members 212 or tines facilitates manipulation of the ureteral catheters 112, 114 from the bladder catheter 116 and through the bladder. Particularly, the open arrangement of the members 212 or tines does not obstruct or occlude the distal opening 248 and/or drainage ports of the bladder catheter 216, making manipulation of the catheters 112, 114 easier to perform.
With reference to
With reference again to
Exemplary Connectors and Clamps:
With reference to
Once the catheters 112, 114 are mounted to the connector 150, urine entering the connector 150 through the vacuum inflow ports 154, 155 is directed through a fluid conduit in the direction of arrow A2 (shown in
With specific reference to
In some examples, urine received in the vacuum ports 154, 155 can be directed through a Y-shaped conduit to a single vacuum outflow port 158 located on a proximal side 160 of the connector 150. As in previously-described examples, the vacuum outflow port 158 can be connected to the fluid collection container 712 and/or pump 710 by suitable flexible tubing or other conduits for drawing urine from the body and for inducing negative pressure in the ureters and/or kidneys. In some examples, the outflow port 156 and/or connector 150 can be configured to attach only to vacuum sources or pumps operating within a predetermined pressure range or power level to prevent exposing the ureteral catheters 112, 114 to elevated levels or intensity of negative pressure. The proximal side 160 of the connector 150 can also comprise a gravity outflow port 162 in fluid communication with the inflow port 156. The gravity outflow port 162 can be configured to be connected directly to the urine collection container 712 for urine collection by gravity drainage.
With continued reference to
Exemplary Fluid Sensors:
With reference again to
Exemplary sensors 174 that can be used with the urine collection assembly 100 can comprise one or more of the following sensor types. For example, the catheter assembly 100 can comprise a conductance sensor or electrode that samples conductivity of urine. The normal conductance of human urine is about 5-10 mS/m. Urine having a conductance outside of the expected range can indicate that the patient is experiencing a physiological problem, which requires further treatment or analysis. The catheter assembly 100 can also comprise a flow meter for measuring a flow rate of urine through the catheter(s) 112, 114, 116. Flow rate can be used to determine a total volume of fluid excreted from the body. The catheter(s) 112, 114, 116 can also comprise a thermometer for measuring urine temperature. Urine temperature can be used to collaborate the conductance sensor. Urine temperature can also be used for monitoring purposes, as urine temperature outside of a physiologically normal range can be indicative of certain physiological conditions. In some examples, the sensors 174 can be urine analyte sensors configured to measure a concentration of creatinine and/or proteins in urine. For example, various conductivity sensors and optical spectrometry sensors may be used for determining analyte concentration in urine. Sensors based on color change reagent test strips may also be used for this purpose.
Method of Insertion of a Urine Collection Assembly:
Having described the urine collection assembly 100 including the ureteral catheter retention portions and bladder anchor device (e.g., a standard or modified Foley-type catheter), methods for insertion and deployment of the assemblies will now be discussed in detail.
With reference to
After the ureteral catheter is in place and deployed, the same guidewire can be used to position a second ureteral catheter in the other ureter and/or kidney using the same insertion and positioning methods described herein. For example, the cystoscope can be used to obtain visualization of the other ureteral opening in the bladder, and the guidewire can be advanced through the visualized ureteral opening to a fluid collection position in the other ureter. A catheter can be drawn alongside the guidewire and deployed in the manner described herein. Alternatively, the cystoscope and guidewire can be removed from the body. The cystoscope can be reinserted into the bladder over the first ureteral catheter. The cystoscope is used, in the manner described above, to obtain visualization of the ureteral opening and to assist in advancing a second guidewire to the second ureter and/or kidney for positioning of the second ureteral catheter. Once the ureteral catheters are in place, in some examples, the guidewire and cystoscope are removed. In other examples, the cystoscope and/or guidewire can remain in the bladder to assist with placement of the bladder catheter.
Optionally, a bladder catheter can also be used. Once the ureteral catheters are in place, as shown at box 620, the medical professional or caregiver can insert a distal end of a bladder catheter in a collapsed or contracted state through the urethra of the patient and into the bladder. The bladder catheter can be a conventional Foley bladder catheter or a bladder catheter of the present invention as discussed in detail above. Once inserted in the bladder, as shown at box 622, an anchor connected to and/or associated with the bladder catheter is expanded to a deployed position. For example, when an expandable or inflatable catheter is used, fluid may be directed through an inflation lumen of the bladder catheter to expand a balloon structure located in the patient's bladder. In some examples, the bladder catheter is inserted through the urethra and into the bladder without using a guidewire and/or cystoscope. In other examples, the bladder catheter is inserted over the same guidewire used to position the ureteral catheters. Accordingly, when inserted in this manner, the ureteral catheters can be arranged to extend from the distal end of the bladder catheter and, optionally, proximal ends of the ureteral catheters can be arranged to terminate in a drainage lumen of the bladder catheter.
In some examples, the urine is permitted to drain by gravity from the urethra. In other examples, a negative pressure is induced in the ureteral catheter and/or bladder catheter to facilitate drainage of the urine.
With reference to
Once the catheter(s) and pump assembly are connected, negative pressure is applied to the renal pelvis and/or kidney and/or bladder through the drainage lumens of the ureteral catheters and/or bladder catheter, as shown at box 626. The negative pressure is intended to counter congestion mediated interstitial hydrostatic pressures due to elevated intra-abdominal pressure and consequential or elevated renal venous pressure or renal lymphatic pressure. The applied negative pressure is therefore capable of increasing flow of filtrate through the medullary tubules and of decreasing water and sodium re-absorption.
In some examples, mechanical stimulation can be provided to portions of the ureters and/or renal pelvis to supplement or modify therapeutic affects obtained by application of negative pressure. For example, mechanical stimulation devices, such as linear actuators and other known devices for providing, for example, vibration waves, disposed in distal portions of the ureteral catheter(s) can be actuated. While not intending to be bound by theory, it is believed that such stimulation effects adjacent tissues by, for example, stimulating nerves and/or actuating peristaltic muscles associated with the ureter(s) and/or renal pelvis. Stimulation of nerves and activation of muscles may produce changes in pressure gradients or pressure levels in surrounding tissues and organs which may contribute to or, in some cases, enhance therapeutic benefits of negative pressure therapy. In some examples, the mechanical stimulation can comprise pulsating stimulation. In other examples, low levels of mechanical stimulation can be provided continuously as negative pressure is being provided through the ureteral catheter(s). In other examples, inflatable portions of the ureteral catheter could be inflated and deflated in a pulsating manner to stimulate adjacent nerve and muscle tissue, in a similar manner to actuation of the mechanical stimulation devices described herein.
As a result of the applied negative pressure, as shown at box 628, urine is drawn into the catheter at the plurality of drainage ports at the distal end thereof, through the drainage lumen of the catheter, and to a fluid collection container for disposal. As the urine is being drawn to the collection container, at box 630, sensors disposed in the fluid collection system provide a number of measurements about the urine that can be used to assess the volume of urine collected, as well as information about the physical condition of the patient and composition of the urine produced. In some examples, the information obtained by the sensors is processed, as shown at box 632, by a processor associated with the pump and/or with another patient monitoring device and, at box 634, is displayed to the user via a visual display of an associated feedback device.
Exemplary Fluid Collection System:
Having described an exemplary urine collection assembly and method of positioning such an assembly in the patient's body, with reference to
As shown in
In some examples, the controller 714 is incorporated in a separate and remote electronic device in communication with the pump 710, such as a dedicated electronic device, computer, tablet PC, or smart phone. Alternatively, the controller 714 can be included in the pump 710 and, for example, can control both a user interface for manually operating the pump 710, as well as system functions such as receiving and processing information from the sensors 174.
The controller 714 is configured to receive information from the one or more sensors 174 and to store the information in the associated computer-readable memory 716. For example, the controller 714 can be configured to receive information from the sensor 174 at a predetermined rate, such as once every second, and to determine a conductance based on the received information. In some examples, the algorithm for calculating conductance can also include other sensor measurements, such as urine temperature, to obtain a more robust determination of conductance.
The controller 714 can also be configured to calculate patient physical statistics or diagnostic indicators that illustrate changes in the patient's condition over time. For example, the system 700 can be configured to identify an amount of total sodium excreted. The total sodium excreted may be based, for example, on a combination of flow rate and conductance over a period of time.
With continued reference to
In some examples, the feedback device 720 further comprises a user interface module or component that allows the user to control operation of the pump 710. For example, the user can engage or turn off the pump 710 via the user interface. The user can also adjust pressure applied by the pump 710 to achieve a greater magnitude or rate of sodium excretion and fluid removal.
Optionally, the feedback device 720 and/or pump 710 further comprise a data transmitter 722 for sending information from the device 720 and/or pump 710 to other electronic devices or computer networks. The data transmitter 722 can utilize a short-range or long-range data communications protocol. An example of a short-range data transmission protocol is Bluetooth®. Long-range data transmission networks include, for example, Wi-Fi or cellular networks. The data transmitter 722 can send information to a patient's physician or caregiver to inform the physician or caregiver about the patient's current condition. Alternatively, or in addition, information can be sent from the data transmitter 722 to existing databases or information storage locations, such as, for example, to include the recorded information in a patient's electronic health record (EHR).
With continued reference to
Non-invasive patient monitoring sensors 724 can include pulse oximetry sensors, blood pressure sensors, heart rate sensors, and respiration sensors (e.g., a capnography sensor). Invasive patient monitoring sensors 724 can include invasive blood pressure sensors, glucose sensors, blood velocity sensors, hemoglobin sensors, hematocrit sensors, protein sensors, creatinine sensors, and others. In still other examples, sensors may be associated with an extracorporeal blood system or circuit and configured to measure parameters of blood passing through tubing of the extracorporeal system. For example, analyte sensors, such as capacitance sensors or optical spectroscopy sensors, may be associated with tubing of the extracorporeal blood system to measure parameter values of the patient's blood as it passes through the tubing. The patient monitoring sensors 724 can be in wired or wireless communication with the pump 710 and/or controller 714.
In some examples, the controller 714 is configured to cause the pump 710 to provide treatment for a patient based information obtained from the urine analyte sensor 174 and/or patient monitoring sensors 724, such as blood monitoring sensors. For example, pump 710 operating parameters can be adjusted based on changes in the patient's blood hematocrit ratio, blood protein concertation, creatinine concentration, urine output volume, urine protein concentration (e.g., albumin), and other parameters. For example, the controller 714 can be configured to receive information about a blood hematocrit ratio or creatinine concentration of the patient from the patient monitoring sensors 724 and/or analyte sensors 174. The controller 714 can be configured to adjust operating parameters of the pump 710 based on the blood and/or urine measurements. In other examples, hematocrit ratio may be measured from blood samples periodically obtained from the patient. Results of the tests can be manually or automatically provided to the controller 714 for processing and analysis.
As discussed herein, measured hematocrit values for the patient can be compared to predetermined threshold or clinically acceptable values for the general population. Generally, hematocrit levels for females are lower than for males. In other examples, measured hematocrit values can be compared to patient baseline values obtained prior to a surgical procedure. When the measured hematocrit value is increased to within the acceptable range, the pump 710 may be turned off ceasing application of negative pressure to the ureter or kidneys. In a similar manner, the intensity of negative pressure can be adjusted based on measured parameter values. For example, as the patient's measured parameters begin to approach the acceptable range, intensity of negative pressure being applied to the ureter and kidneys can be reduced. In contrast, if an undesirable trend (e.g., a decrease in hematocrit value, urine output rate, and/or creatinine clearance) is identified, the intensity of negative pressure can be increased in order to produce a positive physiological result. For example, the pump 710 may be configured to begin by providing a low level of negative pressure (e.g., between about 0.1 mmHg and 10 mmHg). The negative pressure may be incrementally increased until a positive trend in patient creatinine level is observed. However, generally, negative pressure provided by the pump 710 will not exceed about 50 mmHg.
With reference to
In some examples, the pump 710 is configured for extended use and, thus, is capable of maintaining precise suction for extended periods of time, for example, for about 8 hours to about 24 hours per day, for 1 to about 30 days or longer. Further, in some examples, the pump 710 is configured to be manually operated and, in that case, includes a control panel 718 that allows a user to set a desired suction value. The pump 710 can also include a controller or processor, which can be the same controller that operates the system 700 or can be a separate processor dedicated for operation of the pump 710. In either case, the processor is configured for both receiving instructions for manual operation of the pump and for automatically operating the pump 710 according to predetermined operating parameters. Alternatively, or in addition, operation of the pump 710 can be controlled by the processor based on feedback received from the plurality of sensors associated with the catheter.
In some examples, the processor is configured to cause the pump 710 to operate intermittently. For example, the pump 710 may be configured to emit pulses of negative pressure followed by periods in which no negative pressure is provided. In other examples, the pump 710 can be configured to alternate between providing negative pressure and positive pressure to produce an alternating flush and pump effect. For example, a positive pressure of about 0.1 mmHg to 20 mmHg, and preferably about 5 mmHg to 20 mmHg can be provided followed by a negative pressure ranging from about 0.1 mmHg to 50 mmHg.
Treatment for Removing Excess Fluid from a Patient with Hemodilution
According to another aspect of the disclosure, a method for removing excess fluid from a patient with hemodilution is provided. In some examples, hemodilution can refer to an increase in a volume of plasma in relation to red blood cells and/or a reduced concentration of red blood cells in circulation, as may occur when a patient is provided with an excessive amount of fluid. The method can involve measuring and/or monitoring patient hematocrit levels to determine when hemodilution has been adequately addressed. Low hematocrit levels are a common post-surgical or post-trauma condition that can lead to undesirable therapeutic outcomes. As such, management of hemodilution and confirming that hematocrit levels return to normal ranges is a desirable therapeutic result for surgical and post-surgical patient care.
Steps for removing excess fluid from a patient using the devices and systems described herein are illustrated in
As shown at box 912, the method further comprises applying negative pressure to the ureter and/or kidney through the catheter to induce production of urine in the kidney(s) and to extract urine from the patient. Desirably, negative pressure is applied for a period of time sufficient to reduce the patient's blood creatinine levels by a clinically significant amount.
Negative pressure may continue to be applied for a predetermined period of time. For example, a user may be instructed to operate the pump for the duration of a surgical procedure or for a time period selected based on physiological characteristics of the patient. In other examples, patient condition may be monitored to determine when sufficient treatment has been provided. For example, as shown at box 914, the method may further comprise monitoring the patient to determine when to cease applying negative pressure to the patient's ureter and/or kidneys. In a preferred and non-limiting example, a patient's hematocrit level is measured. For example, patient monitoring devices may be used to periodically obtain hematocrit values. In other examples, blood samples may be drawn periodically to directly measure hematocrit. In some examples, concentration and/or volume of urine expelled from the body through the catheter may also be monitored to determine a rate at which urine is being produced by the kidneys. In a similar manner, expelled urine output may be monitored to determine protein concentration and/or creatinine clearance rate for the patient. Reduced creatinine and protein concentration in urine may be indicative of over-dilution and/or depressed renal function. Measured values can be compared to the predetermined threshold values to assess whether negative pressure therapy is improving patient condition, and should be modified or discontinued. For example, as discussed herein, a desirable range for patient hematocrit may be between 25% and 40%. In other preferred and non-limiting examples, as described herein, patient body weight may be measured and compared to a dry body weight. Changes in measured patient body weight demonstrate that fluid is being removed from the body. As such, a return to dry body weight represents that hemodilution has been appropriately managed and the patient is not over-diluted.
As shown at box 916, a user may cause the pump to cease providing negative pressure therapy when a positive result is identified. In a similar manner, patient blood parameters may be monitored to assess effectiveness of the negative pressure being applied to the patient's kidneys. For example, a capacitance or analyte sensor may be placed in fluid communication with tubing of an extracorporeal blood management system. The sensor may be used to measure information representative of blood protein, oxygen, creatinine, and/or hematocrit levels. Measured blood parameter values may be measured continuously or periodically and compared to various threshold or clinically acceptable values. Negative pressure may continue to be applied to the patient's kidney or ureter until a measured parameter value falls within a clinically acceptable range. Once a measured values fails within the threshold or clinically acceptable range, as shown at box 916, application of negative pressure may cease.
Treatment of Patients Undergoing a Fluid Resuscitation Procedure
According to another aspect of the disclosure, a method for removing excess fluid for a patient undergoing a fluid resuscitation procedure, such as coronary graft bypass surgery, by removing excess fluid from the patient is provided. During fluid resuscitation, solutions such as saline solutions and/or starch solutions, are introduced to the patient's bloodstream by a suitable fluid delivery process, such as an intravenous drip. For example, in some surgical procedures, a patient may be supplied with between 5 and 10 times a normal daily intake of fluid. Fluid replacement or fluid resuscitation can be provided to replace bodily fluids lost through sweating, bleeding, dehydration, and similar processes. In the case of a surgical procedure such as coronary graft bypass, fluid resuscitation is provided to help maintain a patient's fluid balance and blood pressure within an appropriate rate. Acute kidney injury (AKI) is a known complication of coronary artery graft bypass surgery. AKI is associated with a prolonged hospital stay and increased morbidity and mortality, even for patients who do not progress to renal failure. See Kim, et al., Relationship between a perioperative intravenous fluid administration strategy and acute kidney injury following off-pump coronary artery bypass surgery: an observational study, Critical Care 19:350 (1995). Introducing fluid to blood also reduces hematocrit levels which has been shown to further increase mortality and morbidity. Research has also demonstrated that introducing saline solution to a patient may depress renal functional and/or inhibit natural fluid management processes. As such, appropriate monitoring and control of renal function may produce improved outcomes and, in particular, may reduce post-operative instances of AKI.
A method of treating a patient undergoing fluid resuscitation is illustrated in
As shown at box 1012, optionally, a bladder catheter may also be deployed in the patient's bladder. For example, the bladder catheter may be positioned to seal the urethra opening to prevent passage of urine from the body through the urethra. The bladder catheter can include an inflatable anchor (e.g., a Foley catheter) for maintaining the distal end of the catheter in the bladder. As described herein, other arrangements of coils and helices may also be used to obtain proper positioning of the bladder catheter. The bladder catheter can be configured to collect urine which entered the patient's bladder prior to placement of the ureteral catheter(s). The bladder catheter may also collect urine which flows past the fluid collection portion(s) of the ureteral catheter and enters the bladder. In some examples, a proximal portion of the ureteral catheter may be positioned in a drainage lumen of the bladder catheter. In a similar manner, the bladder catheter may be advanced into the bladder using the same guidewire used for positioning of the ureteral catheter(s). In some examples, negative pressure may be provided to the bladder through the drainage lumen of the bladder catheter. In other examples, negative pressure may only be applied to the ureteral catheter(s). In that case, the bladder catheter drains by gravity.
As shown at box 1014, following deployment of the ureteral catheter(s), negative pressure is applied to the ureter and/or kidney through the ureteral catheter(s). For example, negative pressure can be applied for a period of time sufficient to extract urine comprising a portion of the fluid provided to the patient during the fluid resuscitation procedure. As described herein, negative pressure can be provided by an external pump connected to a proximal end or port of the catheter. The pump can be operated continually or periodically dependent on therapeutic requirements of the patient. In some cases, the pump may alternate between applying negative pressure and positive pressure.
Negative pressure may continue to be applied for a predetermined period of time. For example, a user may be instructed to operate the pump for the duration of a surgical procedure or for a time period selected based on physiological characteristics of the patient. In other examples, patient condition may be monitored to determine when a sufficient amount of fluid has been drawn from the patient. For example, as shown at box 1016, fluid expelled from the body may be collected and a total volume of obtained fluid may be monitored. In that case, the pump can continue to operate until a predetermined fluid volume has been collected from the ureteral and/or bladder catheters. The predetermined fluid volume may be based, for example, on a volume of fluid provided to the patient prior to and during the surgical procedure. As shown at box 1018, application of negative pressure to the ureter and/or kidneys is stopped when the collected total volume of fluid exceeds the predetermined fluid volume.
In other examples, operation of the pump can be determined based on measured physiological parameters of the patient, such as measured creatinine clearance, blood creatinine level, or hematocrit ratio. For example, as shown at box 1020, urine collected form the patient may be analyzed by one or more sensors associated with the catheter and/or pump. The sensor can be a capacitance sensor, analyte sensor, optical sensor, or similar device configured to measure urine analyte concentration. In a similar manner, as shown at box 1022, a patient's blood creatinine or hematocrit level could be analyzed based on information obtain from the patient monitoring sensors discussed hereinabove. For example, a capacitance sensor may be placed in an existing extracorporeal blood system. Information obtained by the capacitance sensor may be analyzed to determine a patient's hematocrit ratio. The measured hematocrit ratio may be compared to certain expected or therapeutically acceptable values. The pump may continue to apply negative pressure to the patient's ureter and/or kidney until measured values within the therapeutically acceptable range are obtained. Once a therapeutically acceptable value is obtained, application of negative pressure may be stopped as shown at box 1018.
In other examples, as shown at box 2024, patient body weight may be measured to assess whether fluid is being removed from the patient by the applied negative pressure therapy. For example, a patient's measured bodyweight (including fluid introduced during a fluid resuscitation procedure) can be compared to a patient's dry body weight. As used herein, dry weights is defined as normal body weight measured when a patient is not over-diluted. For example, a patient who is not experiencing one or more of: elevated blood pressure, lightheadedness or cramping, swelling of legs, feet, arms, hands, or around the eyes, and who is breathing comfortably, likely does not have excess fluid. A weight measured when the patient is not experiencing such symptoms can be a dry body weight. Patient weight can be measured periodically until the measured weight approaches the dry body weight. When the measured weight approaches (e.g., is within between 5% and 10% of dry body weight), as shown at box 1018, application of negative pressure can be stopped.
Inducement of negative pressure within the renal pelvis of farm swine was performed for the purpose of evaluating effects of negative pressure therapy on renal congestion in the kidney. An objective of these studies was to demonstrate whether a negative pressure delivered into the renal pelvis significantly increases urine output in a swine model of renal congestion. In Example 1, a pediatric Fogarty catheter, normally used in embolectomy or bronchoscopy applications, was used in the swine model solely for proof of principle for inducement of negative pressure in the renal pelvis. It is not suggested that a Fogarty catheter be used in humans in clinical settings to avoid injury of urinary tract tissues. In Example 2, the ureteral catheter 112 shown in
Method
Four farm swine 800 were used for purposes of evaluating effects of negative pressure therapy on renal congestion in the kidney. As shown in
Urine output of two animals was collected for a 15 minute period to establish a baseline for urine output volume and rate. Urine output of the right kidney 802 and the left kidney 804 were measured individually and found to vary considerably. Creatinine clearance values were also determined.
Renal congestion (e.g., congestion or reduced blood flow in the veins of the kidney) was induced in the right kidney 802 and the left kidney 804 of the animal 800 by partially occluding the inferior vena cava (IVC) with an inflatable balloon catheter 850 just above to the renal vein outflow. Pressure sensors were used to measure IVC pressure. Normal IVC pressures were 1-4 mmHg. By inflating the balloon of the catheter 850 to approximately three quarters of the IVC diameter, the IVC pressures were elevated to between 15-25 mmHg. Inflation of the balloon to approximately three quarters of IVC diameter resulted in a 50-85% reduction in urine output. Full occlusion generated IVC pressures above 28 mmHg and was associated with at least a 95% reduction in urine output.
One kidney of each animal 800 was not treated and served as a control (“the control kidney 802”). The ureteral catheter 812 extending from the control kidney was connected to a fluid collection container 819 for determining fluid levels. One kidney (“the treated kidney 804”) of each animal was treated with negative pressure from a negative pressure source (e.g., a therapy pump 818 in combination with a regulator designed to more accurately control the low magnitude of negative pressures) connected to the ureteral catheter 814. The pump 818 was an Air Cadet Vacuum Pump from Cole-Parmer Instrument Company (Model No. EW-07530-85). The pump 818 was connected in series to the regulator. The regulator was a V-800 Series Miniature Precision Vacuum Regulator—⅛ NPT Ports (Model No. V-800-10-W/K), manufactured by Airtrol Components Inc.
The pump 818 was actuated to induce negative pressure within the renal pelvis 820, 821 of the treated kidney according to the following protocol. First, the effect of negative pressure was investigated in the normal state (e.g., without inflating the IVC balloon). Four different pressure levels (−2, −10, −15, and −20 mmHg) were applied for 15 minutes each and the rate of urine produced and creatinine clearance were determined. Pressure levels were controlled and determined at the regulator. Following the −20 mmHg therapy, the IVC balloon was inflated to increase the pressure by 15-20 mmHg. The same four negative pressure levels were applied. Urine output rate and creatinine clearance rate for the congested control kidney 802 and treated kidney 804 were obtained. The animals 800 were subject to congestion by partial occlusion of the IVC for 90 minutes. Treatment was provided for 60 minutes of the 90 minute congestion period.
Following collection of urine output and creatinine clearance data, kidneys from one animal were subjected to gross examination then fixed in a 10% neutral buffered formalin. Following gross examination, histological sections were obtained, examined, and magnified images of the sections were captured. The sections were examined using an upright Olympus BX41 light microscope and images were captured using an Olympus DP25 digital camera. Specifically, photomicrograph images of the sampled tissues were obtained at low magnification (20× original magnification) and high magnification (100× original magnification). The obtained images were subjected to histological evaluation. The purpose of the evaluation was to examine the tissue histologically and to qualitatively characterize congestion and tubular degeneration for the obtained samples.
Surface mapping analysis was also performed on obtained slides of the kidney tissue. Specifically, the samples were stained and analyzed to evaluate differences in size of tubules for treated and untreated kidneys. Image processing techniques calculated a number and/or relative percentage of pixels with different coloration in the stained images. Calculated measurement data was used to determine volumes of different anatomical structures.
Results
Urine Output and Creatinine Clearance
Urine output rates were highly variable. Three sources of variation in urine output rate were observed during the study. The inter-individual and hemodynamic variability were anticipated sources of variability known in the art. A third source of variation in urine output, upon information and belief believed to be previously unknown, was identified in the experiments discussed herein, namely, contralateral intra-individual variability in urine output.
Baseline urine output rates were 0.79 ml/min for one kidney and 1.07 ml/min for the other kidney (e.g., a 26% difference). The urine output rate is a mean rate calculated from urine output rates for each animal.
When congestion was provided by inflating the IVC balloon, the treated kidney urine output dropped from 0.79 ml/min to 0.12 ml/min (15.2% of baseline). In comparison, the control kidney urine output rate during congestion dropped from 1.07 ml/min to 0.09 ml/min (8.4% of baseline). Based on urine output rates, a relative increase in treated kidney urine output compared to control kidney urine output was calculated, according to the following equation:
Thus, the relative increase in treated kidney urine output rate was 180.6% compared to control. This result shows a greater magnitude of decrease in urine production caused by congestion on the control side when compared to the treatment side. Presenting results as a relative percentage difference in urine output adjusts for differences in urine output between kidneys.
Creatinine clearance measurements for baseline, congested, and treated portions for one of the animals are shown in
Gross Examination and Histological Evaluation
Based on gross examination of the control kidney (right kidney) and treated kidney (left kidney), it was determined that the control kidney had a uniformly dark red-brown color, which corresponds with more congestion in the control kidney compared to the treated kidney. Qualitative evaluation of the magnified section images also noted increased congestion in the control kidney compared to the treated kidney. Specifically, as shown in Table 1, the treated kidney exhibited lower levels of congestion and tubular degeneration compared to the control kidney. The following qualitative scale was used for evaluation of the obtained slides.
Congestion
Tubular Degeneration
As shown in Table 1, the treated kidney (left kidney) exhibited only mild congestion and tubular degeneration. In contrast, the control kidney (right kidney) exhibited moderate congestion and tubular degeneration. These results were obtained by analysis of the slides discussed below.
Surface mapping analysis provided the following results. The treated kidney was determined to have 1.5 times greater fluid volume in Bowman's space and 2 times greater fluid volume in tubule lumen. Increased fluid volume in Bowman's space and the tubule lumen corresponds to increased urine output. In addition, the treated kidney was determined to have 5 times less blood volume in capillaries compared to the control kidney. The increased volume in the treated kidney appears to be a result of (1) a decrease in individual capillary size compared to the control and (2) an increase in the number of capillaries without visible red blood cells in the treated kidney compared to the control kidney, an indicator of less congestion in the treated organ.
Summary
These results indicate that the control kidney had more congestion and more tubules with intraluminal hyaline casts, which represent protein-rich intraluminal material, compared to the treated kidney. Accordingly, the treated kidney exhibits a lower degree of loss of renal function. While not intending to be bound by theory, it is believed that as severe congestion develops in the kidney, hypoxemia of the organ follows. Hypoxemia interferes with oxidative phosphorylation within the organ (e.g., ATP production). Loss of ATP and/or a decrease in ATP production inhibits the active transport of proteins causing intraluminal protein content to increase, which manifests as hyaline casts. The number of renal tubules with intraluminal hyaline casts correlates with the degree of loss of renal function. Accordingly, the reduced number of tubules in the treated left kidney is believed to be physiologically significant. While not intending to be bound by theory, it is believed that these results show that damage to the kidney can be prevented or inhibited by applying negative pressure to a catheter inserted into the renal pelvis to facilitate urine output.
Method
Four (4) farm swine (A, B, C, D) were sedated and anesthetized. Vitals for each of the swine were monitored throughout the experiment and cardiac output was measured at the end of each 30-minute phase of the study. Ureteral catheters, such as the ureteral catheter 112 shown in
The ureteral catheters were positioned to extend from the renal pelvis of the swine, through the bladder, and urethra, and to fluid collection containers external to each swine. Following placement of the ureteral catheters, pressure sensors for measuring IVC pressure were placed in the IVC at a position distal to the renal veins. An inflatable balloon catheter, specifically a PTS® percutaneous balloon catheter (30 mm diameter by 5 cm length), manufactured by NuMED Inc. of Hopkinton, N.Y., was expanded in the IVC at a position proximal to the renal veins. A thermodilution catheter, specifically a Swan-Ganz thermodilution pulmonary artery catheter manufactured by Edwards Lifesciences Corp. of Irvine, Calif., was then placed in the pulmonary artery for the purpose of measuring cardiac output.
Initially, baseline urine output was measured for 30 minutes, and blood and urine samples were collected for biochemical analysis. Following the 30-minute baseline period, the balloon catheter was inflated to increase IVC pressure from a baseline pressure of 1-4 mmHg to an elevated congested pressure of about 20 mmHg (+/−5 mmHg). A congestion baseline was then collected for 30 minutes with corresponding blood and urine analysis.
At the end of the congestion period, the elevated congested IVC pressure was maintained and negative pressure diuresis treatment was provided for swine A and swine C. Specifically, the swine (A, C) were treated by applying a negative pressure of −25 mmHg through the ureteral catheters with a pump. As in previously-discussed examples, the pump was an Air Cadet Vacuum Pump from Cole-Parmer Instrument Company (Model No. EW-07530-85). The pump was connected in series to a regulator. The regulator was a V-800 Series Miniature Precision Vacuum Regulator—⅛ NPT Ports (Model No. V-800-10-W/K), manufactured by Airtrol Components Inc. The swine were observed for 120 minutes, as treatment was provided. Blood and urine collection were performed every 30 minutes, during the treatment period. Two of the swine (B, D) were treated as congested controls (e.g., negative pressure was not applied to the renal pelvis through the ureteral catheters), meaning that the two swine (B, D) did not receive negative pressure diuresis therapy.
Following collection of urine output and creatinine clearance data for the 120-minute treatment period, the animals were sacrificed and kidneys from each animal were subjected to gross examination. Following gross examination, histological sections were obtained and examined, and magnified images of the sections were captured.
Results
Measurements collected during the Baseline, Congestion, and Treatment periods are provided in Table 2. Specifically, urine output, serum creatinine, and urinary creatinine measurements were obtained for each time period. These values allow for the calculation of a measured creatinine clearance as follows:
In addition, Neutrophil gelatinase-associated lipocalin (NGAL) values were measured from serum samples obtained for each time period and Kidney Injury Molecule 1 (KIM-1) values were measured from the urine samples obtained for each time period. Qualitative histological findings determined from review of the obtained histological sections are also included in Table 2.
Animal A: The animal weighed 50.6 kg and had a baseline urine output rate of 3.01 ml/min, a baseline serum creatinine of 0.8 mg/dl, and a measured CrCl of 261 ml/min. It is noted that these measurements, aside from serum creatinine, were uncharacteristically high relative to other animals studied. Congestion was associated with a 98% reduction in urine output rate (0.06 ml/min) and a >99% reduction in CrCl (1.0 ml/min). Treatment with negative pressure applied through the ureteral catheters was associated with urine output and CrCl of 17% and 12%, respectively, of baseline values, and 9× and >10×, respectively, of congestion values. Levels of NGAL changed throughout the experiment, ranging from 68% of baseline during congestion to 258% of baseline after 90 minutes of therapy. The final value was 130% of baseline. Levels of KIM-1 were 6 times and 4 times of baseline for the first two 30-minute windows after baseline assessment, before increasing to 68×, 52×, and 63× of baseline values, respectively, for the last three collection periods. The 2-hour serum creatinine was 1.3 mg/dl. Histological examination revealed an overall congestion level, measured by blood volume in capillary space, of 2.4%. Histological examination also noted several tubules with intraluminal hyaline casts and some degree of tubular epithelial degeneration, a finding consistent with cellular damage.
Animal B: The animal weighed 50.2 kg and had a baseline urine output rate of 2.62 ml/min and a measured CrCl of 172 ml/min (also higher than anticipated). Congestion was associated with an 80% reduction in urine output rate (0.5 ml/min) and an 83% reduction in CrCl (30 ml/min). At 50 minutes into the congestion (20 minutes after the congestion baseline period), the animal experienced an abrupt drop in mean arterial pressure and respiration rate, followed by tachycardia. The anesthesiologist administered a dose of phenylephrine (75 mg) to avert cardiogenic shock. Phenylephrine is indicated for intravenous administration when blood pressure drops below safe levels during anesthesia. However, since the experiment was testing the impact of congestion on renal physiology, administration of phenylephrine confounded the remainder of the experiment.
Animal C: The animal weighed 39.8 kg and had a baseline urine output rate of 0.47 ml/min, a baseline serum creatinine of 3.2 mg/dl, and a measured CrCl of 5.4 ml/min. Congestion was associated with a 75% reduction in urine output (0.12 ml/min) and a 79% reduction in CrCl (1.6 ml/min). It was determined that baseline NGAL levels were >5× the upper limit of normal (ULN). Treatment with negative pressure applied to the renal pelvis through the ureteral catheters was associated with a normalization of urine output (101% of baseline) and a 341% improvement in CrCl (18.2 ml/min). Levels of NGAL changed throughout the experiment, ranging from 84% of baseline during congestion to 47% to 84% of baseline between 30 and 90 minutes. The final value was 115% of baseline. Levels of KIM-1 decreased 40% from baseline within the first 30 minutes of congestion, before increasing to 8.7×, 6.7×, 6.6×, and 8× of baseline values, respectively, for the remaining 30-minute windows. Serum creatinine level at 2 hours was 3.1 mg/dl. Histological examination revealed an overall congestion level, measured by blood volume in capillary space, of 0.9%. The tubules were noted to be histologically normal.
Animal D: The animal weighed 38.2 kg and had a baseline urine output of 0.98 ml/min, a baseline serum creatinine of 1.0 mg/dl, and a measured CrCl of 46.8 ml/min. Congestion was associated with a 75% reduction in urine output rate (0.24 ml/min) and a 65% reduction in Cr Cl (16.2 ml/min). Continued congestion was associated with a 66% to 91% reduction of urine output and 89% to 71% reduction in CrCl. Levels of NGAL changed throughout the experiment, ranging from 127% of baseline during congestion to a final value of 209% of baseline. Levels of KIM-1 remained between 1× and 2× of baseline for the first two 30-minute windows after baseline assessment, before increasing to 190×, 219×, and 201× of baseline values for the last three 30-minute periods. The 2-hour serum creatinine level was 1.7 mg/dl. Histological examination revealed an overall congestion level 2.44× greater than that observed in tissue samples for the treated animals (A, C) with an average capillary size 2.33 times greater than that observed in either of the treated animals. The histological evaluation also noted several tubules with intraluminal hyaline casts as well as tubular epithelial degeneration, indicating substantial cellular damage.
Summary
While not intending to be bound by theory, it is believed that the collected data supports the hypothesis that venous congestion creates a physiologically significant impact on renal function. In particular, it was observed that elevation of the renal vein pressure reduced urine output by 75% to 98% within seconds. The association between elevations in biomarkers of tubular injury and histological damage is consistent with the degree of venous congestion generated, both in terms of magnitude and duration of the injury.
The data also appears to support the hypothesis that venous congestion decreases the filtration gradients in the medullary nephrons by altering the interstitial pressures. The change appears to directly contribute to the hypoxia and cellular injury within medullary nephrons. While this model does not mimic the clinical condition of AKI, it does provide insight into the mechanical sustaining injury.
The data also appears to support the hypothesis that applying negative pressure to the renal pelvis through ureteral catheters can increase urine output in a venous congestion model. In particular, negative pressure treatment was associated with increases in urine output and creatinine clearance that would be clinically significant. Physiologically meaningful decreases in medullary capillary volume and smaller elevations in biomarkers of tubular injury were also observed. Thus, it appears that by increasing urine output rate and decreasing interstitial pressures in medullary nephrons, negative pressure therapy may directly decrease congestion. While not intending to be bound by theory, by decreasing congestion, it may be concluded that negative pressure therapy reduces hypoxia and its downstream effects within the kidney in a venous congestion mediated AKI.
The experimental results appear to support the hypothesis that the degree of congestion, both in terms of the magnitude of pressure and duration, is associated with the degree of cellular injury observed. Specifically, an association between the degree of urine output reduction and the histological damage was observed. For example, treated Swine A, which had a 98% reduction in urine output, experienced more damage than treated Swine C, which had a 75% reduction in urine output. As would be expected, control Swine D, which was subjected to a 75% reduction in urine output without benefit of therapy for two and a half hours, exhibited the most histological damage. These findings are broadly consistent with human data demonstrating an increased risk for AKI onset with greater venous congestion. See e.g., Legrand, M. et al., Association between systemic hemodynamics and septic acute kidney injury in critically ill patients: a retrospective observational study. Critical Care 17:R278-86, 2013.
Method
Inducement of negative pressure within the renal pelvis of farm swine was performed for the purpose of evaluating effects of negative pressure therapy on hemodilution of the blood. An objective of these studies was to demonstrate whether a negative pressure delivered into the renal pelvis significantly increases urine output in a swine model of fluid resuscitation.
Two pigs were sedated and anesthetized using ketamine, midazolam, isoflurane and propofol. One animal (#6543) was treated with a ureteral catheter and negative pressure therapy as described herein. The other, which received a Foley type bladder catheter, served as a control (#6566). Following placement of the catheters, the animals were transferred to a sling and monitored for 24 hours.
Fluid overload was induced in both animals with a constant infusion of saline (125 mL/hour) during the 24 hour follow-up. Urine output volume was measured at 15 minute increments for 24 hours. Blood and urine samples were collected at 4 hour increments. As shown in
Results
Both animals received 7 L of saline over the 24 hour period. The treated animal produced 4.22 L of urine while the control produced 2.11 L. At the end of 24 hours, the control had retained 4.94 L of the 7 L administered, while the treated animal retained 2.81 L of the 7 L administered.
Summary
While not intending to be bound by theory, it is believed that the collected data supports the hypothesis that fluid overload induces clinically significant impact on renal function and, consequently induces hemodilution. In particular, it was observed that administration of large quantities of intravenous saline cannot be effectively removed by even healthy kidneys. The resulting fluid accumulation leads to hemodilution. The data also appears to support the hypothesis that applying negative pressure diuresis therapy to fluid overloaded animals can increase urine output, improve net fluid balance and decrease the impact of fluid resuscitation on development of hemodilution.
The preceding examples and embodiments of the invention have been described with reference to various examples. Modifications and alterations will occur to others upon reading and understanding the foregoing examples. Accordingly, the foregoing examples are not to be construed as limiting the disclosure.
This application is a continuation of U.S. patent application Ser. No. 15/687,083, filed Aug. 25, 2017, which is a continuation-in-part of U.S. patent application Ser. No. 15/411,884 filed Jan. 20, 2017, now issued as U.S. Pat. No. 10,512,713, which is a continuation-in-part of U.S. patent application Ser. No. 15/214,955 filed Jul. 20, 2016, now issued as U.S. Pat. No. 10,307,564, which claims the benefit of U.S. Provisional Application No. 62/300,025 filed Feb. 25, 2016, U.S. Provisional Application No. 62/278,721, filed Jan. 14, 2016, U.S. Provisional Application No. 62/260,966 filed Nov. 30, 2015, and U.S. Provisional Application No. 62/194,585, filed Jul. 20, 2015, each of which is incorporated herein by reference in its entirety.
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