WO2000012167A1

WO2000012167A1 - Catheter guide

Info

Publication number: WO2000012167A1
Application number: PCT/AU1999/000689
Authority: WO
Inventors: Ross Cyril Smith
Original assignee: Microcatheters Pty. Ltd.
Priority date: 1998-08-26
Filing date: 1999-08-26
Publication date: 2000-03-09
Also published as: AUPP550098A0

Abstract

A catheter guide (200) for guiding a fine bore catheter into a cannula, including a housing (201) having a distal end configured to fit into the open end of a cannula and separable into two parts, and guide path means to receive a catheter tube, the guide path means supporting the catheter tube in a substantially straight line. Means for engaging and pushing the catheter tube (203) inside the guide path and a retractable needle and flashback chamber are also disclosed.

Description

Catheter guide Field of the Invention

This invention relates to a catheter guide. In particular, the invention relates to a catheter guide for use in inserting such a catheter tube, typically a fine bore catheter tube, into a cannula.

Background of the Invention

As used in this specification, and in the appended claims, the term fine bore catheter tube means a catheter tube having an outside diameter of less than about 2 mm (which would normally imply an internal bore of less than 1.5 mm diameter]. Fine bore catheter tubes can have outside diameters as small as 0.6 mm. The term fine bore catheter as used herein means either a catheter including a fine bore catheter tube (i.e. a catheter hub and a fine bore catheter tube secured to that hub, or a fine bore catheter tube per se. Fine bore silicone catheters allow long term phlebitis (inflammation) free infusion of intravenous nutrition into peripheral veins such as leg and arm veins. The also create less trauma to a patient's body tissue than a large bore catheter and have a wider range of applications than a large bore catheter. Such a fine bore catheter can be as effective a large bore catheter centrally placed in a main vein in the torso or the chest of a patient such as an infraclavicular sub clavian or jugular vein. Placing a larger catheter in a main vein has inherent risks: in particular damage to the vein and surrounding structures and thrombosis can occur. Dedicated specialised support teams are required to monitor patients subjected to central venous cannulation yet the risks persist. The current method for placing catheters in peripheral veins requires taxing hand to eye coordination and uses risky "catheter through needle" techniques with which it is possible to cut the catheter tube on the needle being used to introduce the catheter into peripheral veins, and thus requires specially trained personnel. Thus, because of the problems associated with introducing fine bore catheters into peripheral veins, central venous cannulation despite the potentially life threatening risks, remains the current method of choice of administration of intravenous nutrition.

In the applicant's co-pending international patent application WO 96/33764, a system for introducing a fine bore catheter into a vein is described which includes a cannula unit comprising an elongate tubular sheath defining a distal end and a proximal end and a hub enclosing the proximal end of the sheath. The cannula unit is adapted to receive an introducing needle for introducing the distal end of the sheath of the cannula into a vein. The system also includes a catheter unit having a distal end and a proximal end, a body portion being located at the proximal end of the catheter unit and a fine bore catheter tube extending from the body portion to the distal end of the catheter unit. The hub of the cannula unit defines guide means adapted to receive and guide the distal end of the catheter of the tube into the proximal end of the cannula sheath so that the catheter tube can be guided into and then fed along the sheath. The hub of a cannula unit is adapted to receive and enclose at least a part of the hub of the catheter in a locking arrangement which substantially prevents the catheter hub moving relative to the hub of the cannula unit. In use, the introducing needle is inserted into the cannula unit and used to pierce a vein of a patient and thus introduce the distal end of the cannula sheath into a vein. The introducer needle is then removed and the catheter tube is inserted into the cannula.

To avoid contaminating the catheter tube, the insertion of the catheter tube into the cannula is carried out using forceps and normally the surgeon inserting the catheter tube into the cannula would hold the cannula against the patient's body to prevent the cannula moving and traumatising the patient, and attempt to use his other hand to try and guide the bore of the catheter into the cannula and thus into the patient's vein using the forceps. However, despite the system described above being a considerable improvement on the existing catheter through needle technique described above, it is still an awkward procedure to insert the catheter tube in an efficient and aseptic manner since fine bore catheter tubes are very flexible particularly when compared with larger bore catheters which are stiffer. The present invention seeks to further improve on the system described in WO 96/33764 (the entire contents of which are incorporated herein by reference). One existing solution to the problem of introducing (large bore) catheters into veins and the like without contaminating the catheter has been the provision of a sheath is disposed around the catheter so that the catheter can be handled with the surgeons hands rather than forceps, the sheath being peeled off after handling so that the actual catheter tube itself is not touched and contaminated. However, in the case of fine bore catheters it is difficult to feel and manipulate the catheter through the sheath. The present invention seeks to provide a device which allows more efficient handling of a catheter particularly a fine bore catheter and that may assist in reducing the risk of insertion complications.

Summary of the Invention

According to a first aspect of the present invention there is provided a catheter guide including: a housing having a proximal end and a distal end, the distal end being configured to fit into an open end of a hub of a suitably configured cannula, the housing defining a guide path means located inside the housing which guide path means is adapted to receive a catheter tube, the guide path means being adapted for supporting the catheter tube in a preferably substantially straight line from the proximal end of the housing to the distal end to allow feeding of the catheter along the guide path means through the guide and out of the distal end.

In a particularly preferred embodiment the guide is separable or openable to allow removal of the catheter tube from the guide path means of the housing.

Typically the guide path means will be adapted for receiving a fine bore catheter and have a diameter of about 2mm or less.

The catheter guide preferably has two wings extending laterally from each side of the centre of the housing. This feature enables a user to grasp the catheter guide without risking touching the catheter tube that is to be inserted into the cannula and thence into the vein of a patient. Further, when the catheter guide is inserted into a cannula having a configuration such as is described in WO 96/33764, the wings locate and secure the guide means preventing the guide and catheter from becoming dislodged from the cannula during the insertion procedure and enabling the user (such as a nurse or healthcare professional) to operate (i.e. insert the catheter tube) with two free hands.

It is preferred that the guide path means is of uniform dimension along its entire length (i.e. of substantially constant diameter) such that no articles are encountered by the catheter tube that would disrupt passage of the catheter tube through the housing. It is preferred that the guide is manufactured from a plastics material such as PVC or nylon. In a preferred embodiment, the catheter guide is manufactured in two substantially identical halves. It is preferred that the two halves are fixed together by means of a pin and socket design in which pins and sockets are located at the proximal end of the guide and the base of the pins is approximately as wide as or marginally wider than, the width of the socket so that the two components of the catheter guide are biased apart slightly at the distal end.

According to a second aspect of the present invention there is provided a catheter guide including: a housing having a proximal end and a distal end, the distal end being configured to fit into an open end of a hub of a suitably configured cannula, the housing defining a guide path means located inside the housing which guide path means is adapted to receive a catheter tube, typically a fine bore catheter tube, the guide path means being adapted for supporting the catheter tube in a preferably substantially straight line from the proximal end of the housing to the distal end and including a means for indirectly or remotely engaging the catheter tube inside the guide path means and pushing the same along the guide path means,

In a preferred embodiment the means for engaging the catheter tube includes a wheel which is mounted in the catheter guide on a shaft and which defines an external rim which can be pushed by a user to turn the wheel about its axis and an engaging surface such as a flange defined between the rim of the wheel and the shaft the arrangement being such that the catheter guiding surface may be rotated about the shaft by means of a person touching the rim and without the need for a person to touch the catheter engaging surface.

It is preferred that the catheter guide is separable into two parts or openable to disengage the catheter guide from the catheter.

The catheter guide may define wings for engaging in corresponding slots in a suitably configured cannula unit.

In a related aspect the present invention provides an assembly comprising a length of catheter tubing typically between 10 and 60 cm long defining a proximal end and a distal end, the distal end being incorporated in a catheter hub, with a catheter guide having the first or second aspects as described above being provided at the proximal end of the catheter tubing with a small length, preferably a few millimetres, of catheter tubing protruding beyond the distal end of the catheter guide, the assembly being sealed in a package which is aseptic and/or sterilisable.

A third aspect of the present invention provides a catheter guide including: a housing having a proximal end and a distal end, the distal end being configured to fit into an open end of a hub of a suitably configured cannula. the housing defining a guide path means located inside the housing which guide path means is adapted to receive a catheter tube, typically a fine bore catheter tube, the guide path means being adapted for supporting the catheter tube in a line from the proximal end of the housing to the distal end, the housing further defining a substantially straight bore separate from the guide path means at the proximal end of the housing but which merges with the guide path means at or near the distal end of the housing: and a means for indirectly or remotely engaging the catheter tube inside the guide path means and pushing the catheter tube along the guide path means; and wherein the bore is adapted to receive a retractable needle the arrangement being such that after the needle has punctured a patient's vein, the needle may be retracted along the bore to allow the catheter tube to be fed through the guide means into the cannula.

In a particular embodiment a needle is disposed in the bore in a retracted position so that the guide can be inserted into the catheter with the needle retracted and venipuncture occurs when the needle is pushed along the bore and into the cannula and thence into a patient's vein. The distal end of the needle may be provided with a grip or handle for pushing the needle and the open distal end of the needle may be in sealed fluid communication with a blood flashback chamber.

Particularly when a catheter tube is located in an at least partly blocking the track means, this particular construction minimises blood spillage at the time of needle insertion as well as protecting against needlestick injuries.

Further, the use of the same component for venipuncture and catheter insertion reduces the number of steps required to be taken by the inserter, no connections are required at the insertion site and this reduces the opportunities for contamination of the components. In a particularly preferred embodiment the means for engaging the catheter tube includes a wheel which is mounted in the catheter guide on a shaft and which defines an external rim which can be pushed by a user to turn the wheel about its axis and an engaging surface such as a flange defined between the rim of the wheel and the shaft the arrangement being such that the catheter guiding surface may be rotated about the shaft by means of a person touching the rim and without the need for a person to touch the catheter engaging surface.

The guide path means may be substantially straight and may be oriented at an angle of about 5 to 30 degrees relative to the bore.

The grip means may define two bores, one for receiving the needle, the other for receiving an elongate projection extending rearwards from the proximal end of the guide parallel to the bore of the guide and along which the grip can slide to move the needle relative to the guide. Preferably the device includes a needle engagement means to prevent re-use of the needle and guide after it had been used once.

The present invention also provides an assembly comprising a length of catheter tubing typically between 10 and 60 cm long defining a proximal end and a distal end, the distal end being incorporated in a catheter hub, with a catheter guide of the third aspect as described above being provided at the proximal end of the catheter tubing with the distal end of the catheter tubing located in the guide means of the catheter guide, the assembly including a needle and being sealed in a package which is aseptic and/or sterilisable. The invention also provides a method of inserting a fine bore catheter into a vein comprising the steps of:- a). inserting a catheter guide including a retractable needle into a hub of a cannula, positioning the cannula on a patient for puncture of a chosen vein with the needle tip projecting from the cannula and piercing the patient's vein: b). checking that the needle has pierced the vein by means of a blood flashback chamber associated with the needle; c). retracting the needle to remove it from the cannula; and d). using the guide means to guide a catheter tube into the vein via the cannula. The invention has numerous advantages over the prior art in particular providing a sterile "no-touch" technique for inserting fine bore catheters.

Brief description of the Drawings

A specific embodiment of the present invention will now be described, by way of example only, and with reference to the accompanying drawings in which:

Figure 1 is a perspective drawing of an introducer needle unit a cannula and a catheter partially inserted into that cannula;

Figure 2 is a plan view of one half of a catheter guide embodying the present invention;

Figure 3 is a section on line III III shown in Figure 2; and

Figure 4 is a part section on line IV IV shown in Figure 2 showing one half (component) of the guide only;

Figure 5 is a perspective view of a second embodiment of a catheter guide;

Figure 6 is a schematic side view of a similar catheter guide to that of Figure 5 when inserted in a cannula; Figure 7 is a section on lines VII- VII of Figure 6;

Figure 8 is a schematic side view of a yet further embodiment of the present invention; and

Figures 9 to 11 show stages in the introduction of a catheter using the embodiment of Figure 8.

Detailed Description of a Preferred Embodiment

Referring to the drawings, Figure 1 shows components of system for inserting a fine bore catheter into a vein comprising an introducing needle unit 10, a cannula unit generally indicated at 30 and a catheter hub generally indicated at 50.

The introducing needle unit 10 defines a hub which has a proximal end 10A and a distal end 10B. From the proximal end 10A, the needle unit hub defines a main body portion 12 which is generally cylindrical but which is contoured with a series circumferentially extending ribs 14, a conical portion 16 and an enlarged bulbous portion 18 which is generally ellipsoid in shape. The proximal end of the cylindrical body portion defines a central bore 20 which has a standard luer taper. A needle 11 extends from the distal end of the needle unit as far as the junction between the conical portion and the cylindrical portion of the needle hub.

The cannula unit 30 has a proximal end 30A and a distal end 30B. It comprises an elongate sheath or cannula tube 32 defining a cylindrical bore and a hub portion generally indicated at 34. In the Figure only a part of the sheath 32 is visible. From the proximal end 30A, the hub defines a generally bell shape portion 36 from which extend two flat wing portions 38, 40. The bell shaped portion 36 defines a generally bell shaped internal cavity including a depending skirt portion through which two slots 42, 44 extend from the proximal end 30A of the hub of the cannula unit and which terminate in an enlarged generally circular opening of which only one 46 is visible in Figure 1.

The catheter unit 50 has a proximal end 50A and a distal end 50B. The distal end of the catheter hub 51 defines a conical portion 52 which tapers towards a generally ellipsoid shape protrusion or plug 54. Two diametrically opposed cylindrical stubs of which only one numbered 56 is visible, protrude from the catheter. The catheter tube 58 is fixed to the distal end 50B of the catheter body. Both the introducer needle and the catheter hub are configured to fit inside the cannula. In particular, the conical and ellipsoid portions locate inside the bell shaped portion of the cannula with the protrusions on the catheter hub preventing the same from moving or rotating relative to the cannula hub. As described in the introduction to this specification, problems can arise when feeding the fine bore catheter tube 58 into the hub of the cannula 30 through the cannula sheath 32 and into the vein of a patient. Figure 2 shows a catheter guide generally indicated at 100, which can be utilised to alleviate that problem. The catheter guide 100 has a proximal end 100A and a distal end

100B and includes a centre 101 and wings 106, 108. From the proximal end 100A the centre of the catheter guide comprises a generally cylindrical but slightly tapering, central portion 102 and a generally ellipsoid portion 104 which terminates at the distal end 100B of the catheter guide. Wings 106, 108 extend laterally from the centre portion 102 of the housing. The total width of the housing including the wings is approximately 20 mm, a preferred range for that width being 15 to 40 mm.

A longitudinal bore 110 of approximately 2 mm diameter which defines a guide path extends through the centre 101, best seen in Figure 3. The catheter guide is made of two identical halves or components

112, 114 which are held together by a pin and socket means defined on the wings 106, 108. The sockets 116 are generally cylindrical and are defined in protrusions 118. one socket/protrusion being defined on one wing of each component in an asymmetric arrangement (refer to Figure 3). The plugs 120 have a generally cylindrical portion 122 adjacent the wing and a distal truncated conical portion 124. On the opposite side of the wing to the plug there is a protrusion whose external shape and size is substantially identical to the shape of protrusions 118. The protrusions 126. 118 can be used to grip and manipulate the catheter guide. The pins and sockets principally engage by means of friction of the cylindrical portions 122 in the sockets with relatively little force and this allows the catheter guide to be separated in two and removed from this location around a catheter bore with minimal disruption to the catheter tube 58. Further, tabs 128 on either side of the assembled catheter guide provides extra leverage when separating the two halves of the catheter guide.

The provision of the wings enables the catheter guide to securely locate in a cannula made to the design of the cannula 30 shown in Figure 1 with the wings locating in slots 42,44. The fact that both components of the assembled guide 100 are identical reduces the moulding costs for making the guide.

In use the catheter 50 and assembled catheter guide 100 can be provided in a sealed aseptic package with the catheter guide already located around the distal end of the catheter tubing 58 associated with the catheter hub. with the catheter tubing positioned inside the bore or guide path 110 of the catheter guide. The package can be opened and the catheter guide conveniently grasped by the operator by means of the two laterally extending wings 106. 108. with a short section of the catheter tubing protruding from the distal end of the guide. The protruding section is then inserted into the open end of a suitably configured cannula such as a cannula 30 and the catheter tubing guided into the vein of the patient via the guide and cannula. The guide locks in the cannula by means of the wings 106, 108 engaging in slots 42, 44. Forceps can be used to push the catheter tube through the catheter guide (the bore 110 being lightly wider than the tubing), through the sheath into the vein. The fact that a portion of the catheter is maintained straight by the catheter guide assists in this. This method of insertion is possible since guide is locked in the cannula and the operator can use two free hands. When the desired length of catheter tubing has been introduced, the catheter guide may be removed from the cannula by the lateral wings and separated into two. Instead of separation into two a hinge arrangement could also be provided which would enable the guide to open to disengage/remove the catheter tube from the bore of the guide.

Thus the present invention provides a catheter guide which can be used to guide tubing into a introducing cannula without the necessity of precise hand to eye coordination. The invention also reduces the possibility of trauma and infection at the insertion sight as the guide assists in inserting the catheter efficiently and aseptically. Once the guide has been removed, the catheter can be secured and dressed in a standard manner.

Figures 5 to 7 show two further catheter guides generally indicated at 200. The design of the guide shown in Figure 5 is slightly different to the guide shown in Figures 6 and 7, however the differences are largely cosmetic and the principal of operation of the two embodiments is the same. Similar components in the Figures share the same reference numerals.

The catheter guide 200 includes a body portion 201 defining a longitudinal central axis 202. The guide is generally rotationally symmetrical about its central axis 202 apart from the upper part of the catheter body portion 201 in which a wheel 203 is mounted, to be described in detail below. As shown in Figure 6, the body portion 201 of the catheter guide comprises a first ellipsoid portion 204 and a second larger generally ellipsoid body portion 206 in which the abovementioned wheel 203 is mounted. As illustrated in Figure 6, the small ellipsoid body portion 204 is configured to fit inside the cannula unit 30 shown in Figure 1. Along the central axis of the catheter guide there is a longitudinal bore or guide path 202A best seen in Figure 7 which is approximately the same diameter as the fine bore catheter 58 (i.e. about 2mm). The body portion of the catheter guide of Figures 6 and 7 is made in two parts 201A and 201B joined along a vertically oriented plane 208 passing though the axis 202. As is best seen in Figure 7, when the two parts are conjoined a vertically extending slot 210 is defined between the plates. The slot is configured to receive the wheel 203, thus in side view, the slot is generally arcuate. Two plates 212, 214 extend up from the body portion 201. A generally keyhole-shaped slot 216 is defined in each plate.

The wheel 203, as is best seen in Figure 7, includes a central integral shaft 218 which is mounted in a lower part of the hole 216 defined in each of two spaced apart plates 212, 214. A flange is defined at each distal end of the shaft. Each flange is wider than the lower part of the slot, to lock the wheel in the slot. The wheel has an external surface or rim 220 which is serrated and defines a second circular flange surface 222 of a lesser diameter than the wheel. As the wheel rotates the part of the flange surface 222A below the central shaft of the wheel contacts the catheter 58 in the central bore of the catheter guide as illustrated in Figure 7. Rotation of the wheel by pressing the serrated external rim 220 will engage the catheter between the body of the catheter guide and the flange 222 of the wheel and cause the catheter to move along the guide path of the catheter guide along axis 202. Thus the catheter guide can be used for feeding a fine bore catheter

58 into a cannula as illustrated in Figure 6.

As illustrated in Figure 5, a protective sheath 250 may be attached over the catheter guide so the catheter has no contact with dust or air and the risk of infection to an open insertion site and to the length of the catheter to lie inside the vein would be greatly reduced.

The catheter guide is preferably made of a plastics material. The catheter guide of the second and third embodiments of the present invention provides a means to hold a soft fine bore catheter straight and stiff at the point of insertion where the catheter is fed into a cannula. The guide path/track holds the catheter horizontal for the length of the guide path, thus any portion of the fine bore catheter that has been pushed through the track via the wheel will remain supported for the necessary length to ensure insertion. Since the catheter guide is shaped to fit into the cannula in the correct orientation, the fine bore catheter will automatically be guided from the catheter guide through the cannula and into the vein. After the catheter has been inserted to the desired position in the vein, the catheter guide is removed from the cannula and the catheter tube by splitting the catheter guide into two portions.

The catheter guide may include wings for locking the guide into the cannula 30.

The present invention obviates the need for the use of secondary tools such as forceps and hands in servicing fine bore catheter tubes.

In the embodiment shown in Figure 5. the split occurs along a horizontal line 240 where the two parts of the catheter are joined in contrast with the embodiment shown in Figures 6 and 7 the split is along the vertical line 208.

Figures 8 to 11 show a yet further embodiment of a guide 300 of the present invention which is similar to those shown in figures 5 to 7. However in this embodiment the introducer needle 10 is not required. The catheter guide includes a body portion 302 which at its front or distal end defines a first ellipsoid portion 304 which is adapted to be received in the hub of the cannula 30.

An elongate rod 306 extends away from the body portion 302 of the guide. The body portion of the guide defines two bores 308, 310. Bore 308 extends through the body of the guide along an axis which is spaced from and generally parallel to the axis 306 of the rod. The other bore extends from the proximal or rear end of the guide above the rod along a line which is generally at an angle of approximately 10° to that of bore 308 and which meets and merges with bore 308 at the distal, or front end. of the guide, A wheel 312 is provided for feeding a catheter guide along the bore 310 and the structure of the wheel is similar to that of the embodiments shown in Figures 5 to 7 having an external rim 314 which may be touched by the surgeon or health care worker and a flange 316 of a lesser diameter than the rim 314 which contacts the fine bore catheter as it is pushed through the bore/guide path 310.

A grip or handle 320 is mounted on the rod 306 and is slidable therealong. A needle 322 has its proximal end 324 fixedly mounted in the grip 320 and extends from the grip parallel to the rod 306 and into the bore 308. An end 326 is provided at the end of the rod 306 to prevent the guide 320 from sliding off the rod 306. A tube 326 extends from the end of the needle 322 and is in fluid communication with the needle and extends back to a flash back chamber 328. In Figure 8 the tube 326 is shown shortened so that all the components of the guide can be shown in the Figure.

When using the guide in a first step, the grip 320 and needle 322 are mounted to guide 300 so that are arranged as shown in Figure 8 if they are not already so arranged. In the next stage the guide assembly is inserted into the cannula 30 with the front end 304 locking in the cannula. (Wings may be provided to prevent rotation if desired). At this stage the needle is protected from accidental needle stick injuries since the pointed end of the needle 322 is inside the guide 300. In the next stage the grip 320 is pushed forward so that the needle

322 travels through the bore 308 into the cannula and into the vein. Blood will flash-back along the needle 322 and tube 326 into the flash-back chamber 328 when a vein has been successfully pierced. If a catheter tube is located in the second bore 310 thus should block the bore and prevent any blood from being spilt. All blood should be in the lumen of the cannula or in the flash-back chamber. This arrangement is shown in Figure 9.

Turning to Figure 10, the needle is then retracted by pulling the grip 320 backwards and an arrangement is provided such that when this is done the needle is permanently locked backwards and cannot then be reused. Following that, the wheel 314 is turned in order to feed the catheter tube 58 through the guide means and into the vein. Although Figure 9 does not illustrate the catheter 58 being in the bore 310 at the time the needle pierces the vein, the catheter tube maybe located there at that stage, or alternatively may be inserted into the guide after the vein has been pierced. Once the catheter tube has been inserted into the vein successfully, the guide 300 may be pulled back from engagement with cannula 30 separated into two or more pieces or opened, if hinged, to remove it from around the catheter 58 and the catheter hub 50 can then be locked into the cannula 30. Although all the embodiments described include an ellipsoid portion which is adapted to fit in a matingly configured cannula. it will be appreciated that the front end of the catheter guide could be configured to fit into any cannula or the like and could, for example define a luer taper or lock. Also, although the catheter guides described above are particularly suited for use with fine bore catheters, it will be appreciated that they could be used with larger bore catheters.

It will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the invention as shown in the specific embodiments without departing from the spirit or scope of the invention as broadly described. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.

Claims

1. A catheter guide including: a housing having a proximal end and a distal end, the distal end being configured to fit into an open end of a hub of a suitably configured cannula, the housing defining a guide path means located inside the housing which guide path means is adapted to receive a catheter tube, the guide path means being adapted for supporting the catheter tube in a preferably substantially straight line from the proximal end of the housing to the distal end to allow feeding of the catheter along the guide path means through the guide and out of the distal end.

2. A catheter guide as claimed in claim 1 wherein the guide is separable into two parts or openable so as to allow removal of the catheter tube from the guide path means of the housing.

3. A catheter guide as claimed in any preceding claim wherein the guide path means has a diameter of 2mm or less.

4. A catheter guide as claimed in any preceding claim having two wings extending laterally from each side of the centre of the housing.

5. A catheter guide as claimed in any preceding claim wherein the guide path means is of a substantially constant diameter along its entire length.

6. A catheter guide as claimed in any preceding claim wherein the guide is made from a plastics material such as PVC or nylon.

7. A catheter guide as claimed in any preceding claim wherein the catheter guide is manufactured in two substantially identical halves which may be joined together by means of a pin and socket design in which pins and sockets are located at the proximal end of the guide and the base of the pins is approximately as wide as or marginally wider than, the width of the socket so that the two components of the catheter guide are biased apart slightly at the distal end.

8. A catheter guide including: a housing having a proximal end and a distal end. the distal end being configured to fit into an open end of a hub of a suitably configured cannula. the housing defining a guide path means located inside the housing which guide path means is adapted to receive a catheter tube, typically a fine bore catheter tube, the guide path means being adapted for supporting the catheter tube in a preferably substantially straight line from the proximal end of the housing to the distal end and including a means for indirectly or remotely engaging the catheter tube inside the guide path means and pushing the same along the guide path means.

9. A catheter guide as claimed in claim 8 wherein the means for engaging the catheter tube includes a wheel which is mounted in the catheter guide on a shaft and which defines an external rim which can be pushed by a user to turn the wheel about its axis and an engaging surface such as a flange defined between the rim of the wheel and the shaft the arrangement being such that the catheter guiding surface may be rotated about the shaft by means of a user touching the rim and without the need for that user to touch the catheter engaging surface.

10. A catheter guide as claimed in claim 8 or claim 9 wherein the catheter guide is separable into two parts or openable to disengage the catheter guide from the catheter.

11. A catheter guide as claimed in any one of claims 8 to 9 wherein the catheter guide defines wings for engaging in corresponding slots in a suitably configured cannula unit.

12. A catheter guide and catheter assembly comprising a length of catheter tubing typically between 10 and 60 cm long defining a proximal end and a distal end, the distal end being incorporated in a catheter hub, with a catheter guide according to any preceding claim provided at the proximal end of the catheter tubing with a short length, preferably a few millimetres, of catheter tubing protruding beyond the distal end of the catheter guide, the assembly being sealed in a package which is aseptic and/or sterilisable.

13. A catheter guide including: a housing having a proximal end and a distal end, the distal end being configured to fit into an open end of a hub of a suitably configured cannula, the housing defining a guide path means located inside the housing which track is adapted to receive a catheter tube, typically a fine bore catheter tube, the guide path means being adapted for supporting the catheter tube in a line from the proximal end of the housing to the distal end, the housing further defining a substantially straight bore separate from the track means at the proximal end of the housing but which merges with the track means at or near the distal end of the housing; and a means for engaging the catheter tube inside the guide path means and pushing the catheter tube along the guide path means; and wherein the bore is adapted to receive a retractable needle, the arrangement being such that after the needle has punctured a patient's vein, the needle may be retracted along the bore to allow the catheter tube to be fed through the guide means into the cannula.

14. A catheter guide as claimed in claim 13 wherein a needle is disposed in the bore in a retracted position so that the guide can be inserted into the cannula with the needle retracted

15. A catheter guide as claimed in claim 13 or 14 wherein the distal end of the needle is provided with a grip or handle for pushing the needle and the open distal end of the needle is in fluid communication with a blood flashback chamber.

16. A catheter guide as claimed in any one of claims 13 to 15 wherein the means for engaging the catheter tube is a means for indirectly or remotely engaging the tube including a wheel which is mounted in the catheter guide on a shaft and which defines an external rim which can be pushed by a user to turn the wheel about its axis and an engaging surface such as a flange defined between the rim of the wheel and the shaft the arrangement being such that the catheter guiding surface may be rotated about the shaft by means of a person touching the rim and without the need for the user to touch the catheter engaging surface.

17. A catheter guide as claimed in any one of claims 13 to 16 wherein the guide path means is substantially straight and is oriented at an angle of about 5 to 30 degrees relative to the bore.

18. A catheter guide as claimed in any one of claims 15 to 17 wherein the grip means defines two bores, one for receiving the needle, the other for receiving an elongate projection extending rearwards from the proximal end of the guide parallel to the bore of the guide and along which the grip can slide to move the needle relative to the guide.

19 A catheter guide as claimed in any one of claims 14 to 19 wherein the guide includes a needle engagement means to prevent re-use of the needle and guide after it had been used once.

20. An assembly comprising a length of catheter tubing typically between 10 and 60 cm long defining a proximal end and a distal end, the distal end being incorporated in a catheter hub, with a catheter guide as claimed in any one of claims 13 to 19 provided at the proximal end of the catheter tubing with the distal end of the catheter tubing located in the guide means of the catheter guide, the assembly including a needle and being sealed in a package which is aseptic and/or sterilisable.

21. A method of inserting a fine bore catheter into a vein comprising the steps of:- a), inserting a catheter guide including a retractable needle into a hub of a cannula, positioning the cannula on a patient for puncture of a chosen vein with the needle tip projecting from the cannula and piercing the patient's vein; b). checking that the needle has pierced the vein by means of a blood flashback chamber associated with the needle; c). retracting the needle to remove it from the cannula; and d). using the guide means to guide a catheter tube into the vein via the cannula.

22. The use of a guide as claimed in any one of claims 1 to 20 for inserting a catheter tube into a vein.