Patent Application
20120253279
This invention concerns a method of introducing a catheter into an umbilical artery.
Umbilical artery catheters are frequently used for blood pressure monitoring, and are also used for blood sampling. Severe adverse incidents with such catheters are uncommon, but in trials aortic thrombi have been detected in 30% of cases. Also at a level of around 30% minor perfusion problems in the feet have been encountered, often resolving with contralateral limb warming, at times requiring catheter removal, and occasionally causing loss of digits. The cause is currently thought to be arterial ‘spasm’.
Adverse incidents may occur due to malpositioning of the catheter, and correct positioning is considered to be lower thoracic or lower lumbar aorta. The tip is intended to lie within the aorta. Other adverse incidents may be due to the technique of introduction. One such feature may be the tip of the catheter being contaminated by coming into contact with the cut end of the umbilical stump.
Conventionally the catheter is manually inserted after dilating the cut end of the artery. A no touch technique may be used, but the tip of the catheter becomes exposed to the cut end of the artery, and also at times to the surrounding Wharton's jelly, either directly and/or indirectly by the gloved hand or instruments.
The cut end of the artery contains procoagulants. Wharton's jelly contains substances that cause red cell agglutination. These substances are sufficient cause in the pathogenesis of thrombosis, or minor red cell agglutinations, both involved in the production of arterial emboli, which are a more logical cause of the pattern of symptoms.
According to the present invention there is provided a method of introducing a catheter into an umbilical artery, the method comprising providing a barrier between the distal end of the catheter and the cut end of the artery and surrounding Wharton's jelly, as the catheter is initially introduced into the artery.
The barrier may be removed subsequent to initial introduction of the catheter into the artery.
The artery may be dilated prior to initial introduction of the catheter thereinto, and the dilation may be carried out by any of forceps, an introducer with a rounded end, or an obturator with a rounded end.
In a first embodiment a cannula is provided which lines the inner walls of the proximal end of the artery, and the catheter is slidably movable through the cannula.
The cannula may have a proximal flange which engages against the umbilicus around the end of the artery.
The cannula may be of a sufficient length to extend into a patient's abdomen when located extending into the umbilical artery.
The cannula may be formed such that it can be removed from around the catheter following location of the catheter in the artery. A line of weakness may be provided on the cannula to allow it to be broken open to permit removal from around the catheter.
One or more co-operable formations may be provided on the cannula which enable selective opening and closing thereof, with the catheter removable from the cannula when open.
The cannula may be formed of a plastics material, or alternatively of metal.
The cannula may be selectively locatable on a locating tool, which tool can be used to locate a cannula mounted thereon in the proximal end of the artery, with the cannula removable from the tool once the cannula is in place in the artery.
The locating tool may include an obturator on which the cannula can be located. The locating tool may be made of a flexible material.
The obturator may have a rounded distal end. The obturator may taper towards the distal end thereof. The obturator may be longer than the cannula such that when a cannula is located thereon, the distal end of the obturator extends beyond the cannula.
The locating tool may include a step at the proximal end of the obturator, such that the proximal end of the cannula engages against the step.
The locating tool may also include an introducer engageable in an artery to dilate same. The introducer may have a rounded distal end. The introducer may have a greater diameter than the obturator. The introducer may be provided on an opposite end of the locating tool to the obturator.
In a second embodiment of the invention, a film is provided over the distal end of the catheter prior to introduction into the artery, to close the distal end of the catheter, and the film may be broken following introduction of the catheter into the artery to open the distal end of the catheter.
The film may be made of plastics material. The film may be arranged such that the cannula can pass therethrough once the film has been broken.
Embodiments of the present invention will now be described by way of example only and with reference to the accompanying drawings, in which:
A cannula 30 shown in
To locate a catheter in a one of the arteries 14, the respective artery 14 will be dilated. This may require insertion of the introducer 22, forceps, and/or introduction of the obturator 26. The obturator 26 with the cannula 30 located thereon as shown in
A catheter 38 can then be slowly introduced through the cannula 30, with the distal end of the catheter 38 not engaging with the cut end of the artery 14 and hence the procoagulants therein. Also the distal end of the catheter 38 does not engage with the Wharton's jelly 16 and hence the substances that can cause red cell agglutination. Once the catheter 38 has passed through the cannula 30, and perhaps to a required position, the cannula 30 is slid out of the artery 14 along the catheter.
A further cannula 130 is shown located on the obturator 26. The cannula 130 is of a size to slidingly fit on the obturator 126, and in this instance did not taper towards its distal end 134. Otherwise the cannula 130 has a similar formation to that shown in
It is to be realised that the locating tool and/or cannula can take a number of different forms, and may include any combination of the above described features. For instance a tapering obturator with a rounded end may be used. The locating tool may be made of a flexible material.
There are thus described methods, and apparatus usable with such methods to enable catheters to be inserted into an umbilical artery without the end of the catheter coming into contact with the end of the artery and also the surrounding Wharton's jelly. Accordingly the adverse incidents outlined above can be avoided.
It is to be realised that various other modifications may be made without departing from the scope of the invention. For instance a cannula with a different form could be used. Other methods may be used for initially providing a barrier between the distal end of the catheter.
Whilst endeavouring in the foregoing specification to draw attention to those features of the invention believed to be of particular importance it should be understood that the Applicant claims protection in respect of any patentable feature or combination of features hereinbefore referred to and/or shown in the drawings whether or not particular emphasis has been placed thereon.
| Number | Date | Country | Kind |
|---|---|---|---|
| 1102424.7 | Feb 2011 | GB | national |
