Patent Application
20080114430
The present invention relates generally to patient temperature control systems.
It has been discovered that the medical outcome for a patient suffering from severe brain trauma or from ischemia caused by stroke or heart attack or cardiac arrest is improved if the patient is cooled below normal body temperature (37° C.). Furthermore, it is also accepted that for such patients, it is important to prevent hyperthermia (fever) even if it is decided not to induce hypothermia. Moreover, in certain applications such as post-CABG surgery, it might be desirable to rewarm a hypothermic patient.
As recognized by the present invention, the above-mentioned advantages in regulating temperature can be realized by cooling or heating the patient's entire body. Moreover, the present invention understands that since many patients already are intubated with central venous catheters for other clinically approved purposes anyway such as drug delivery and blood monitoring, providing a central venous catheter that can also cool or heat the blood requires no additional surgical procedures for those patients. The following U.S. patents, all of which are incorporated herein by reference, disclose various intravascular catheters/systems/methods: U.S. Pat. Nos. 6,749,625, 6,786,916, 6,581,403, 6,454,792, 6,436,130, 6,146,411, 6,109,783, 6,419,643, 6,416,533, 6,409,747, 6,405,080, 6,393,320, 6,368,304, 6,338,727, 6,299,599, 6,290,717, 6,287,326, 6,165,207, 6,149,670, 6,146,411, 6,126,684, 6,306,161, 6,264,679, 6,231,594, 6,149,676, 6,149,673, 6,110,168, 5,989,238, 5,879,329, 5,837,003, 6,383,210, 6,379,378, 6,364,899, 6,325,818, 6,312,452, 6,261,312, 6,254,626, 6,251,130, 6,251,129, 6,245,095, 6,238,428, 6,235,048, 6,231,595, 6,224,624, 6,149,677, 6,096,068, 6,042,559, and U.S. patent application Ser. No. 10/355,776. Less optimally, surface cooling can be used. U.S. Pat. Nos. 6,827,728, 6,818,012, 6,802,855, 6,799,063, 6,764,391, 6,692,518, 6,669,715, 6,660,027, 6,648,905, 6,645,232, 6,620,187, 6,461,379, 6,375,674, 6,197,045, and 6,188,930 (collectively, “the external pad patents”), all of which are incorporated herein by reference, disclose such surface cooling systems. In both intravascular catheters and external pad systems, coolant such as a gas or saline is circulated through the heat exchange element.
Regardless of the particular heat exchange element that is engaged with the patient, as understood herein it may be advantageous to use such a system during surgical procedures to control patient temperature. As further understood herein, some procedures may employ another component such as a heart-lung machine (HLM) that can also function to control patient temperature. The present invention understands that during such procedures, a primary temperature control system such as those disclosed in the above patents can be used to assist the other component, e.g., the HLM, in reducing patient temperature to a very low level. However, as further recognized herein it is important to avoid the control processor of one system from “fighting” the control processor of the other system during such assist procedures.
A method includes engaging a heat exchange element with a patient. The heat exchange element is coupled to a primary control system for controlling patient temperature. The method also includes engaging a component such as a heart lung machine (HLM) with the patient for, e.g., cardiac bypass surgery, with the component also controlling patient temperature. The primary control system is used to assist the component in establishing a target patient temperature. Then, at or about target temperature being reached, temperature control functions of the primary control system are suspended so that only the component controls patient temperature.
The heat exchange element can include an intravascular catheter and/or a pad applied externally to a patient's skin.
In another aspect, a system for exchanging heat with primary coolant flowing through a patient-engageable heat exchange element includes a processor executing logic including receiving a target temperature signal, and resetting a low temperature alarm setpoint based on the target temperature signal.
In still another aspect, a method includes engaging a heart-lung machine (HLM) with a patient and engaging a heat exchange element that is not part of the HLM with the patient. The method further includes using both the HLM and heat exchange element to approach a target patient temperature. The method also includes at or about the target temperature, suspending temperature control of the heat exchange element and controlling patient temperature using only the HLM.
The details of the present invention, both as to its structure and operation, can best be understood in reference to the accompanying drawings, in which like reference numerals refer to like parts, and in which:
Referring initially to
In accordance with present principles, the system 10 can be used to induce therapeutic hypothermia in a patient 16 using a catheter in which coolant such as but not limited to saline circulates in a closed loop, such that no coolant enters the body. While certain preferred catheters are disclosed below, it is to be understood that other catheters can be used in accordance with present principles, including, without limitation, any of the catheters disclosed in the following U.S. patents, all incorporated herein by reference: U.S. Pat. Nos. 5,486,208, 5,837,003, 6,110,168, 6,149,673, 6,149,676, 6,231,594, 6,264,679, 6,306,161, 6,235,048, 6,238,428, 6,245,095, 6,251,129, 6,251,130, 6,254,626, 6,261,312, 6,312,452, 6,325,818, 6,409,747, 6,368,304, 6,338,727, 6,299,599, 6,287,326, 6,126,684. The catheter 12 may be placed in the venous system, e.g., in the superior or inferior vena cava. Examples of non-limiting control systems 14 are shown in U.S. Pat. Nos. 6,786,916, 6,581,403, 6,454,792, 6,436,130, 6,146,411, and 6,109,783, incorporated herein by reference.
Instead of or in addition to the catheter 12, the system 10 may include one or more pads 18 that are positioned against the external skin of the patient 16 (only one pad 18 shown for clarity). The pad 18 may be, without limitation, any one of the pads disclosed in the external pad patents. The temperature of the pad 18 can be controlled by a pad controller 20 with processor 22 in accordance with principles set forth in the external pad patents to exchange heat with the patient 16, including to induce therapeutic mild or moderate hypothermia in the patient in response to the patient presenting with, e.g., cardiac arrest, myocardial infarction, stroke, high intracranial pressure, traumatic brain injury, or other malady the effects of which can be ameliorated by hypothermia. The control systems 14, 20 may be implemented by a single system having one or more processors for executing temperature control algorithms in accordance with the referenced patents.
One or both of the primary control systems 14, 20 may be used during, e.g., a surgical procedure such as cardiac bypass surgery that might employ a component such as but not limited to a heart-lung machine (HLM) 24 with component processor 26 that happens to control blood temperature extracorporeally, in addition to other functions it might perform such as blood oxygenation. During some of these procedures it might happen to be desirable to cool the patient to temperatures (e.g., fifteen degrees Centigrade) far lower than those normally used for therapeutic hypothermia (e.g., mild hypothermia temperatures). As recognized herein, one or both of the primary control systems 14, 20 can be used to assist the HLM 24 in lowering patient temperature. It should be understood that while for simplicity the discussion below relates to using only the primary control system 14 with catheter 12 to assist the HLM 24, one or both of the primary control systems 14, 20 can be used to assist the HLM 24.
Now referring to
While the particular TEMPERATURE MANAGEMENT SYSTEM WITH ASSIST MODE FOR USE WITH HEART-LUNG MACHINE is herein shown and described in detail, it is to be understood that the subject matter which is encompassed by the present invention is limited only by the claims.
