GB2333461A

GB2333461A - Epidural catheter

Info

Publication number: GB2333461A
Application number: GB9900117A
Authority: GB
Inventors: Kester Julian Batchelor; John Edward Nash
Original assignee: Smiths Group PLC
Current assignee: Smiths Group PLC
Priority date: 1998-01-23
Filing date: 1999-01-06
Publication date: 1999-07-28
Anticipated expiration: 2019-01-06
Also published as: GB2333461B; EP0931559A3; EP0931559A2; GB9801325D0; GB9900117D0; GB2333461A8

Abstract

Parallel slits 7 in the wall of the an epidural catheter form four strips 8 which are attached at both ends but which can deflect outwardly midway along their length to anchor the catheter in the epidural space. A tether 5 fixed to the patient end 3 of the catheter can be pulled at its machine end 6 to deflect the strips 8 outwardly. Alternatively, the patient end is split into two strips (18) fixed at their rear end only and having a J-shape memory so that they expand when pushed out of an epidural needle.

Description

EPIDURAL CATHETERS This invention relates to epidural catheters.

Epidural catheters are used to administer anaesthetic fluid to the epidural space in order to relieve pain in the lower part of the body. The patient end tip of the catheter is introduced to the epidural space through a needle, which is subsequently removed over the catheter. The catheter is left in place and taped in position where it emerges from the skin.

One problem is that there is a risk that the catheter can be pulled out of the epidural space as the patient moves, because of relative sliding movement between the different tissue layers through which the catheter passes. This can prevent the anaesthetic being administered. In order to reduce this risk, the clinician may insert an extra length of catheter into the epidural space. This extra length of catheter, however, allows the tip to be displaced away from the centre line, thereby increasing the risk of a unilateral block. Also, where an excessive length of catheter is inserted in the epidural space, there is a risk of entanglement of the catheter. In US 5591132 there is described an epidural catheter that forms a curl at its patient end.

It is an object of the present invention to provide an improved epidural catheter.

According to one aspect of the present invention there is provided an epidural catheter having a machine end and a patient end that can be inserted into the epidural space through a needle, a region towards the patient end having at least two deflectable members that can deflect away from one another when outside the needle in the epidural space such as to anchor the patient end in the epidural space.

The deflectable members may possess a memory such that they deflect away from one another when unconfined. The deflectable members may be formed from a part of the wall of the catheter and may be formed by dividing the wall of the catheter in the patient end region with a plurality of parallel slits into a plurality of deflectable strips.

In one form, the deflectable members may be attached with the wall of the catheter at both ends, the deflectable members deflecting outwardly midway along their length. The catheter may include a manually-engageable member extending along the catheter from the patient end region to the machine end, the manually-engageable member being movable along the catheter such as to displace the deflectable members. The manually-engageable member may be either pulled rearwardly to displace the deflectable members outwardly or pushed forwardly to displace the deflectable members inwardly. The manually-engageable is preferably attached with the patient end of the catheter forwardly of the deflectable members.

The patient end tip of the catheter may be closed, the patient end of the catheter opening through the wall of the catheter in the patient end region. The catheter may include four deflectable members around the catheter.

Alternatively, the deflectable members may be attached with the wall of the catheter at their rear ends only such that the forward ends of the deflectable members are deflectable outwardly. The deflectable members may be formed by splitting the catheter in half into two deflectable members.

According to another aspect of the present invention there is provided an assembly of an epidural catheter according to the above one aspect of the invention and an epidural needle, the catheter being inserted within the needle with its patient end emerging from the tip of the needle into the epidural space, the needle being removable rearwardly over the catheter, and the deflectable members at the patient end of the catheter being displaceable outwardly when unconfined by the needle.

The assembly preferably includes an introducer of tubular form into which the patient end of the catheter is inserted and which is held up to the machine end of the needle to enable the patient end of the catheter to be introduced to the needle.

Two forms of epidural catheter according to the present invention, will now be described, by way of exarnple, with reference to the accompanying drawings, in which: Figure 1 is a perspective view of the first form of catheter, in an unexpanded state; Figure 2 is a perspective view of the catheter of Figure 1, in an expanded state; Figure 3 is an enlarged perspective view of the patient end of the catheter of Figures 1 and 2 in an expanded state; Figure 4 is a perspective view of a second form of catheter; Figure 5 is an enlarged perspective view of the patient end of the catheter of Figure 4; and Figure 6 is a perspective view of the catheter of Figures 4 and 5, showing the catheter prior to use.

With reference first to Figures 1 to 3, the catheter has a nylon tubular shaft 1 with a circular section and a diameter of about 1 mum. The length of the catheter is typically about 920mm. The rear, machine end 2 of the catheter is plain so that the needle used to introduce the catheter can be pulled off over the machine end of the catheter. The patient end 3 of the catheter is closed by a bullet-shape tip 4, which is attached to the forward end of a flexible tether 5 extending along the inside of the shaft 1. The rear end of the tether 5 emerges from the rear end 2 of the catheter and is formed with a small loop 6, which is large enough to prevent it entering the bore of the catheter but is small enough to allow it to pass through the bore of the needle used to introduce the catheter. The cross-sectional dimensions of the tether 5 are small enough to allow passage of fluid along the catheter. About 5mm rearwardly of its patient end 3, the wall of the catheter is cut by four parallel slits 7 to divide a region of the catheter into four longitudinally-extending strip members 8 about 1 5mm long. The strips are attached at both ends with the shaft 1. In their natural state, the strip members 8 lie flat, forming a continuation of the cylindrical surface of the remainder of the shaft 1, as shown in Figure 1. It is in this state that the catheter is introduced through a hollow needle into the epidural space, in the usual way.

After removing the needle, the loop 6 is gripped and the tether 5 is pulled, so as to pull the tip 4 rearwardly by about 1 Omm. As this happens, the strip members 8 deflect outwardly away from one another, in the manner shown in Figures 2 and 3, so that the lateral dimensions of the catheter in this region are substantially increased. The expanded cross section of the catheter in this region is sufficient to prevent it being pulled through the path made through the tissue by the needle. This, therefore, anchors the patient end of the catheter in the epidural space until the tether 5 is released. The machine end 2 of the catheter is attached to a modified epidural catheter connector (not shown), which acts to hold the loop 6 in its retracted position and allows anaesthetic liquid to be injected along the catheter. The anaesthetic liquid flows out of the patient end 3 of the catheter through the expanded slits 7 between the strips 8. The catheter could be pulled rearwardly by the clinician, following deflection of the strips 8, until the strips contact the wall of the epidural space. This ensures that the anaesthetic fluid is administered directly at the midline. When the catheter needs to be removed, the loop 6 is released, allowing the resilience of the deflectable strip members 8 to restore them to their original flat state.

With this arrangement, there is a reduced the risk of the patient end of the catheter being pulled out of the epidural space without the need to increase the length of catheter inserted in the epidural space, thereby avoiding the consequent increase in the risk of unilateral block.

It will be appreciated that the natural state of the deflectable members 8 could be such that they are in a laterally expanded state, in which case, the tether would be sufficiently stiff that, when pushed forwardly, it pushes the patient end forwardly and thereby retracts the deflectable members inwardly sufficient for insertion and removal.

Instead of forming the deflectable strips from the wall of the shaft of the catheter itself, they could be formed from a slit sleeve attached over a conventional epidural catheter.

There are various other ways in which an epidural catheter could be provided with deflectable members to anchor the patient end of the catheter in the epidural space. For example, as shown in Figures 4 to 6, the shaft 11 of the catheter could simply be split longitudinally at its patient end 13 into two arms 18. The arms 18 are attached with the shaft at their machine end and are unattached at their patient end. The arms 18 have a plastic memory (such as provided by suitable heat treatment) such that they tend to assume a shape extending laterally away from the axis of the main part of the catheter. The catheter is introduced in the manner shown in Figure 6. The catheter is pulled rearwardly into a needle introducer 20 in the form of a short sleeve having a reduced external diameter at its forward end 21. This brings the arms 18 together. The forward end 21 of the introducer 20 is then inserted into the hub of the epidural needle (not shown) so that the bore of the introducer aligns with the bore of the needle. The catheter is then pushed forwardly out of the introducer and along the bore of the needle, with the arms 18 being held together by the confinement of the needle. When the catheter emerges from the patient end of the needle, in the epidural space, the arms 18 deflect laterally outwardly, by their memory. The needle is then removed over the rear end of the catheter, leaving the catheter in position. The deflected arms 18 anchor the patient end of the catheter in the epidural space. To remove the catheter, it is simply pulled out with sufficient force to close the two arms 18 sufficiently for them to pass through the passage through the tissue made by the epidural needle. This force is greater than that normally experienced as a result of movement of patient tissue. Because the patient end of this form of catheter has relatively large lateral dimensions, there is a low risk of dural tap, that is, of the patient end of the catheter puncturing the dura and entering the spinal cavity.

Claims

CLAIMS 1. kn epidural catheter having a machine end and a patient end that can be inserted into the epidural space through a needle, wherein a region towards the patient end has at least two deflectable members that can deflect away from one another when outside the needle in the epidural space such as to anchor the patient end in the epidural space.
2. An epidural catheter according to Claim 1, wherein the deflectable members possess a memory such that they deflect away from one another when unconfined.
3. An epidural catheter according to Claim 1 or 2, wherein the deflectable members are formed from a part of the wall of the catheter.
4. An epidural catheter according to Claim 3, wherein the deflectable members are formed by dividing the wall of the catheter in the patient end region with a plurality of parallel slits into a plurality of deflectable strips.
5. An epidural catheter according to Claim 3, wherein the deflectable members are attached with the wall of the catheter at both ends, and wherein the deflectable members deflect outwardly midway along their length.
6. An epidural catheter according to any one of the preceding claims, wherein the catheter includes a manually-engageable member extending along the catheter from the patient end region to the machine end, and wherein the manually-engageable member is movable along the catheter such as to displace the deflectable members.
7. An epidural catheter according to Claim 6, wherein the manually-engageable member is pulled rearwardly to displace the deflectable members outwardly.
8. An epidural catheter according to Claim 6, wherein the manually-engageable member is pushed forwardly to displace the deflectable members inwardly.
9. An epidural catheter according to any one of Claims 6 to 8, wherein the manually engageable member is attached with the patient end of the catheter forwardly of the deflectable members.
10. An epidural catheter according to any one of the preceding claims, wherein the patient end tip of the catheter is closed and the patient end of the catheter opens through the wall of the catheter in the patient end region.
11. An epidural catheter according to any one of the preceding claims including four deflectable members around the catheter.
12. An epidural catheter according to any one of Claims 1 to 4, wherein the deflectable members are attached with the wall of the catheter at their rear end only such that the forward end of the deflectable members are deflectable outwardly.
13. An epidural catheter according to Claim 12, wherein the deflectable members are formed by splitting the catheter in half into two deflectable members.
14. An epidural catheter substantially as hereinbefore described with reference to Figures 1 to 3 of the accompanying drawings.
15. An epidural catheter substantially as hereinbefore described with reference to Figures 1 to 3 as modified by Figures 4 to 6 of the accompanying drawings.
16. An assembly of an epidural catheter according to any one of the preceding claims and an epidural needle, the catheter being inserted within the needle with its patient end emerging from the tip of the needle into the epidural space, wherein the needle is removable rearwardly over the catheter, and wherein the deflectable members at the patient end of the catheter are displaceable outwardly when unconfined by said needle.
17. An assembly according to Claim 16 including an introducer of tubular form into which the patient end of the catheter is inserted and which is held up to the machine end of the needle to enable the patient end of the catheter to be introduced to the needle.
18. Any novel and inventive feature as hereinbefore described.