GB2377889A

GB2377889A - Subcutaneous tunnelling

Info

Publication number: GB2377889A
Application number: GB0118113A
Authority: GB
Inventors: Andrew S Kong
Original assignee: Individual
Current assignee: Individual
Priority date: 2001-07-25
Filing date: 2001-07-25
Publication date: 2003-01-29
Also published as: GB0118113D0

Abstract

A tunnelling device 2 for creating a subcutaneous tunnel comprises a stylet 6 and a malleable tubular cannula (4). The stylet 6 has a cutting tip 8 at its proximal end and a handle 10 at its distal end. The cannula (4) sheathes the stylet 6, along a portion of the stylet's length between the handle 10 and the cutting tip 8. The cutting tip 8 projects beyond the proximal end 14 of the cannula (4), and the stylet 6 is axially movable within the cannula (4).

Description

SUBCUTANEOUS TUNNELLING FIELD OF THE INVENTION The present invention relates to subcutaneous tunnelling for securing a catheter, notably an epidural catheter, under a patient's skin. The invention provides a tunnelling device for use in the tunnelling method.

BACKGROUND TO THE INVENTION Medical or surgical procedures for administering fluid to a patient on a long term basis are well known. Typically, a subcutaneous tunnel is made between two locations and a catheter is located in the tunnel to supply fluid between the locations. Such a procedure may be used, for example, in the administration of an analgesic for relieving pain in terminal cancer patients. An epidural catheter extends subcutaneously from the paravertebral site, where it introduces the analgesic into the epidural space, to an exit location some distance away. The analgesic, for example diamorphine, is introduced through a suitable connection to the catheter at the exit location.

A known tunnelling device comprises a solid tunneller having a leading end with a cutting tip and a trailing end over which is slipped the catheter. The catheter is dragged through the tunnel created by the tunneller.

Problems with this tunneller are that the catheter may become kinked, or may slip off the tunneller. Moreover,

an epidural catheter may become dislodged from the epidural space during tunnelling. Another known tunneller is hollow and has openings in the cutting tip and the trailing end of sufficient dimensions to permit the catheter to pass through them. After the tunnel is made, and with the tunneller still in place, the catheter is then threaded through the opening in the tip and out through the trailing end. A problem with this arrangement is that blood or severed tissue from the tunnelling procedure may enter the tunneller through the opening in the tip and clog the passageway through the tunneller so as to inhibit or prevent the threading of the catheter therethrough. A further tunneller is described in US Patent No. 5,171, 226. This comprises a hollow shaft which has a solid removable cutting tip on one end thereof.

After the tunneller has created a subcutaneous passage, the cutting tip projects from the skin and is removed by pulling or unscrewing it from the shaft. Following removal of the solid cutting tip, a catheter may then be passed through the shaft. A problem with this device is that the tip may cut the surgeon during its removal, with consequent risk of blood-borne infection.

The present invention seeks to provide an improved subcutaneous tunnelling device.

DESCRIPTION OF THE INVENTION According to an aspect of the present invention there is provided a tunnelling device for creating a subcutaneous tunnel, the device comprising a stylet having a cutting tip at its proximal end and a handle at its distal end; and a malleable tubular cannula having a proximal end and a distal end ; wherein the cannula sheathes the stylet along a portion of the stylet's length between the handle and the cutting tip, the cutting tip projecting beyond the proximal end of the cannula, and the stylet being axially movable within the cannula.

After tunnelling has located the cannula in the desired location, the stylet is withdrawn therefrom by pulling it back through the distal end of the cannula. This procedure avoids a surgeon or anaesthetist having to handle the cutting tip. A catheter is then threaded through the cannula prior to removal of the cannula to leave the catheter in place in the tunnel.

The device is particularly for use in creating a subcutaneous tunnel in a patient's back, for securing an epidural catheter under the skin, from the point of catheter insertion to a suitable exit point some distance away. For convenience, the invention will be described hereinafter with reference to this use. However, it is to be understood that the invention is not limited to this use.

If the tunnelling device is to be used on a nonanaesthetised patient, a hollow stylet may be used, with openings at the distal end and in the cutting tip connected together by a lumen. This arrangement permits anaesthetic fluid to be provided at the cutting point from a source connected to the distal end of the stylet. A positive pressure of anaesthetic fluid will inhibit blood or cutting debris from entering the tunneller through the opening in the cutting tip. However, because the stylet is completely removed from the cannula after tunnelling, any blood or cutting debris therein will also be removed, leaving the cannula open for a catheter to be threaded through.

The stylet may be formed from any suitable resilient material, for example metal or a structural plastics material. In a preferred embodiment, the stylet is formed from stainless steel. It is preferred that the stylet is malleable so that the operator may, if desired,"shape" the tunnelling device before insertion. In this way the operator can direct and control the depth and direction of the subcutaneous tunnel as the tunneller is advanced under the skin. Typically, the operator will create a slight curve in the tunnelling device to facilitate its passing through and out of the skin at the exit point.

The length of the stylet will depend on the particular operation to be performed and the clinical demands resulting from this. The stylet is preferably from 8 to 22 cm long, notably about 12 to 18 cm, particularly about

15 cm.

The handle of the stylet may be integrally formed with the stylet, or it may be permanently or releasably secured thereto.

The cannula is preferably a snug fit around the stylet, and may be provided with a tapered tip at its proximal end to prevent or reduce ingress of blood or other matter. To minimise the advancement required of the tunnelling device, it is preferred that the cannula covers almost the entire length of the stylet, with its proximal end just shy of the cutting tip.

The material from which the cannula is made must permit the cannula substantially to maintain its shape once the stylet is removed. The cannula may be made of a suitable medical-grade semi-rigid plastics material, for example polytetrafluoroethylene (PTFE) or a vinyl material, or from a metal, for example stainless steel.

The stylet must be axially moveable in the cannula to permit its removal by pulling on completion of the tunnelling operation. However, it is within the scope of the invention to releasably fix the stylet relative to the cannula while the tunnelling operation is being carried out, and then to release the stylet for withdrawal.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will now be further described, by way of example, with reference to the following drawings in which: Figure 1 is sectional view through the cannula of the tunnelling device shown in Figure 3; Figure 2 is a sectional view through a stylet of the tunnelling device shown in Figure 3; Figure 3 is a sectional view through a tunnelling device in accordance with the present invention; and Figure 4 is an enlarged view of the proximal end of the tunnelling device shown in Figure 3.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT The tunnelling device 2 comprises a cannula 4 which sheathes a stylet 6. In this example, the cannula 4 is formed from 16 gauge PTFE.

The stylet 6, in this example formed from stainless steel, is provided with a sharp cutting tip 8. In this example the cutting tip 8 is integrally formed, but it could alternatively be releasably secured to the stylet 6, for example by means of a screw thread or a friction fit, or it could be separately formed but permanently bonded to the stylet. The stylet 6 is malleable, so that it may if desired be shaped into a slight curve to facilitate its passage under a patient's skin and out through an exit point.

The stylet 6 is approximately 15 cm in length. At its distal end it is provided with a handle, in this example a finger-shield 10 of a type known per se, formed from a plastics material. The major surfaces of the finger shield 10 measure about 1 cm x 1 cm. The distal end of the stylet 6 is also provided with an injection port 12, for connection to a source of local anaesthetic fluid.

As best shown in Figure 4, the proximal end 14 of the cannula 4 is tapered so that is closely conforms to the external circumference of the stylet 6. This helps to reduce ingress of blood and cutting debris between the cannula 4 and stylet 6 during use. With the distal end of

the cannula 4 butted against the finger-shield 10, the cutting tip 8 projects a short distance beyond the proximal end 14 of the cannula 4.

After insertion of an epidural catheter (EC) in known manner, a subcutaneous tunnel is created by passing the tunnelling device 2 from a point adjacent to the catheter insertion point to a suitable skin exit site (usually lateral to the insertion site), pointing the cutting tip 8 away from the catheter at all times. The finger-shield 10 is used to advance and direct the stylet 6 in the most appropriate direction. In a non-anaesthetised patient, local anaesthetic solution may be introduced subcutaneously via the injection port 12 as the tunnelling device is advanced.

When the exit site of the tunnel is reached, the stylet 6 is removed by pulling it back through the cannula 4 by means of the finger-shield 10. Care must be taken to leave short lengths of cannula protruding from both ends of the subcutaneous tunnel. The EC is then threaded through the cannula 4; once a sufficient length of EC emerges from the tunnel, the cannula may be withdrawn and removed laterally over the advancing EC. The EC is withdrawn further until its exterior loops completely disappears through the insertion site within the tunnel.

The proximal end of the EC is then connected to an appropriate infusion device in known manner.

For added safety, the following procedure may be followed prior to removal of the stylet. Having located the EC in the epidural space, the epidural needle (for example a Tuohy needle) is partially withdrawn over the EC so that most of the needle remains under the skin (but with its tip out of the epidural space) shielding the EC from the tunnelling stylet 6. The needle is completely withdrawn once the tunnelling stylet has been removed.

Although the invention has been described with reference to a preferred embodiment thereof, the invention is not limited to this embodiment. Many changes may be made without departing from the scope of the invention herein contemplated and the invention is limited only as indicated in the claims.

Claims

CLAIMS 1. A tunnelling device for creating a subcutaneous tunnel, the device comprising a stylet having a cutting tip at its proximal end and a handle at its distal end; and a malleable tubular cannula having a proximal end and a distal end; wherein the cannula sheathes the stylet along a portion of the stylet's length between the handle and the cutting tip, the cutting tip projecting beyond the proximal end of the cannula, and the stylet being axially movable within the cannula.
2. A tunnelling device as claimed in claim 1, wherein the stylet has a lumen therethrough, and the cutting tip and the distal end of the stylet have openings therein, which are connected by the said lumen so as to permit the passage of fluid from the distal end of the stylet through the opening in the cutting tip.
3. A tunnelling device as claimed in claim 1 or claim 2, wherein the proximal end of the cannula is tapered so as to conform closely to the external surface of the stylet.
4. A tunnelling device as claimed in any one of the preceding claims, wherein the handle comprises a fingershield.
5. A tunnelling device as claimed in any one of the preceding claims wherein, when the distal end of the cannula abuts the handle, the cutting tip of the stylet

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projects a short distance beyond the proximal end of the cannula.
6. A tunnelling device as claimed in any one of the preceding claims, wherein the handle is releasably secured to the stylet.
7. A tunnelling device as claimed in claim 2, which is provided with an injection port in fluid communication with the opening in the distal end of the stylet.
8. A tunnelling device as claimed in any one of the preceding claims, wherein the cannula is formed from PTFE.
9. A tunnelling device as claimed in any one of the preceding claims, wherein the stylet is malleable so that it may be deformed to a desired shape.
10. A tunnelling device as claimed in any one of the preceding claims, wherein the stylet is formed from stainless steel.
11. A tunnelling device for creating a subcutaneous tunnel substantially as herein described with reference to or as shown in the drawings.