The present invention refers to a procedure for catheterization of preferably the vascular system in accordance with the introduction of Claim No. 1 and a device for performing same according to the introduction of Claim No. 4.

A previously known device of the same kind is shown and described in SE-A- 404491, the device with the purpose of guiding a catheter into its position in a blood-vessel, consisting of a head part and a sheath with a slit along the entire length of said device, both tubular and head member included. The sheath is made of a flexible material with the slit extending along the complete extension of it. Similar devices are known in US-A-3853130, EP-A-00911434, US-A-3472232, US-A-4619644 and EP-A-0067260.

These previously known devices have the following disadvantages;

US-A-3472232 consists of several movable parts and no wide slot making a deformation of the catheter unavoidable. EP-A-0067260 calls for a deformation to create or enlarge a slit (with the following increase of the outer diameter of the device). US-A→4619644 is not designed for flexible long catheters without stiffening guide- wires that have to be extracted later. Neither US-A-3472232 nor US-A-4619644 are designed for use with the Seldinger technique, the most atraumatic and safe method.

Catheters are introduced into the vascular system to create a link to the outside world. If great and fast dilution exists the administration of highly irritating solutions will be possible. For this reason central vessels close to the heart are catheterized when delivering cytotoxics, certain antibiotics and aminoacids.

A centrally positioned catheter can be connected to a port, subcutaneously placed by surgery, and a system concealed from the outside world will be obtained. When necessary this system can be connected to the outside world by penetrating the silicone top of the port (and the skin) with a special cannula which in turn is connected to an infusion system.

Catheters inserted in "central" veins are soft and highly flexible, in size and consistency like boiled spaghetti, i.e. flexible and soft. In order to penetrate the skin and underlying tissues as well as the wall of a vessel, a tube or sheath through which the catheter will be introduced or, alternatively, a guide-wire over which the catheter will be advanced into the vascular lumen, is required. The intravascularly positioned catheter is connected to infusion-systems via standardized attachments or connected to a subcutaneously placed port. Catheters are often tunnelled in order to minimize the risk of infection or simply for practical reasons, giving the port or catheter a convenient position.

1 Direct method

The direct method implies introduction of the catheter through a sufficiently large cannula after positioning of the latter in the vascular lumen. Disadvantage; Postulates a large cannula (inner-diameter = catheter diameter), and a "stripped" catheter without mounts, attachments or port.

2. Indirect method

A cannula with an enveloping plastic sheath on the outside is introduced into the vascular lumen, the sheath is passed over the cannula into a vessel and the cannula thereafter extracted. The catheter is inserted through the sheath. Disadvantage; Requires a "stripped" catheter. Rather large cannula.

3. Seldinger technique

Method A:

A guide- wire is inserted through a small bore cannula into the lumen. A catheter is threaded over the guide- wire reaching an intraluminar position.

Disadvantage; The guide-wire may not make sharp turns as the friction between catheter and guide-wire at the insertion of the catheter, or extraction of the guide-wire, will be too great and the catheter will get caught. The guide-wire is extracted through the distal end of the catheter making a port impracticable.

Method B:

A guide-wire is introduced into the vascular lumen via a small bore cannula. A plastic sheath with tapered proximal end and plastic tubular sleeve on the outside is pushed or forced into the vessel, and the tubular sleeve pushed in, whereupon the sheath (dilator) and guide- wire is extracted. The catheter is inserted through the remaining tubular sleeve into the lumen and the sleeve is pulled out. The Seldinger technique allows a small bore cannula, (atraumatic).

Disadvantage; Requires "stripped" catheter. The method postulates tunnelling to be made as a last step.

The problems with the methods described above are;

- The sheath or sleeve has to be extracted over a "stripped" catheter by being drawn over the distal end for which reason no port or attachment can be connected to it until later. The connection will then take place under suboptimal conditions.

- When a guide- wire is used it has to be extracted through the distal end of the catheter to which no port can be connected. A catheter advanced over a guide- wire will because of friction easily stick to the guide-wire in shaφ turns and is often caught by surrounding tissues when penetrating narrow passages on the way between skin and vessel. When extracting the guide-wire from the inserted catheter the risk of getting caught is even greater, and shaφ bends may make extraction impossible.

- Tunnelling always has to be made as a last step when using any of the methods described above.

It is, accordingly, the general object of the present invention to provide a technique for catherization, preferably of the central vascular system, and the provision of an insertion device with which this technique becomes possible, eliminating the problems with the present methods described above, not postulating rigid catheters for removal of said device as a condition with this catherization technique, the minimal friction between sheath and catheter preventing the latter from slipping out the least.

An additional object is to minimize the space needed between the catheter coming out of the subcutaneous tunnel and the puncture site of the insertion device a roughly 5 - 10 mm long incision with underlying subcutaneous pocket without restriction in depth.

A further object is to eliminate the risk of kinking when using a flexible catheter.

These objects are achieved according to the invention by both a technique in accordance with the criteria set forth in Claim 1, and a device in accordance with the criteria set forth in Claim 4.

Owing to the technique and the device according to the present invention the problems described above are avoided by the use of an "open" sheath, metal or plastic, with an unbroken head at the distal end. The catheter is inserted in front of the head member through an opening that is insignificantly larger than the diameter of the catheter. The sheath may, proximal to the opening, be provided with a wide slot identical in width to the opening. In this case the opening forms the beginning of the slot, i.e. exhibits a head part and a tubular part equipped with a long slot. Alternatively, the sheath can also, proximal to the opening, be furnished with a slit. In this case the sheath is conveniently made of a thin plastic material.

Existing devices make it necessary for the catheter to be inserted through the head member of the sheath leaving a catheter-loop of several centimeters which after the extraction will give rise to kinking if a flexible catheter is used. In the slot of the device according to the present invention the catheter can be inserted as proximal as possible as the width of the slot exceeds that of the catheter. Insertion of central venous catheters, with or without the use of subcutaneous tunnelling or insertion of subcutaneous ports, is exclusively made with "closed" devices generally utilizing the Seldinger technique.

A simple removal of the sheath from the catheter and a simple construction of the sheath making it economical to manufacture has this far been obstacles for widespread use of "open" sheaths. The device according to the present invention complies with those requirements by adopting an unbroken head member and an opening proximal to it. Being adapted to the Seldinger technique, the method necessitates only a moderate alteration of present techniques, notwithstanding a considerable simplification.

In present kits for introduction of central venous catheters or implantation of ports only one sort of sheath has to be changed for another in order to obtain a substantial improvement of method.

The object of the invention is the provision of a technique and a device for catherization of preferably central veins. When using long, flexible unstiffened catheters for catheterization of central veins it is an advantage to be able to make all necessary connections to attachments or ports in advance and to make the tunnelling prior to the

introduction of the catheter into the vein. This requires an "open" device not extracted over the distal end of the catheter. The device according to the present invention solves this problem by having an open sheath with an open duct or groove forming a slot in front of an unbroken head member. By introducing the catheter proximal to the head a strong head-end is obtained and the groove may therefore be made wider than the catheter. When extracting the sheath the insignificant friction between the catheter and slot makes the use of very flexible catheters possible. The same applies to the alternative thin sheath with an opening and a slit.

The simplicity and function of the design, distinguishing it from other existing "open" devices, makes it possible to replace the totally dominating "closed" techniques with the "open" without increase in complexity or higher costs.

The present invention is described more detailed by reference to the drawings showing presented designs.

Fig. 1 is a bottom elevation of the first design of the device according to the present invention. Fig. 2 is a top elevation of the device. Fig. 3 is a side elevation of the device.

Fig. 4 is a sectional side view of the device, showing the catheter having entered the slot. Fig. 5 is a sectional top elevation of the device.

Fig. 6 is an sectional side view of the proximal part of tubular member of the device, schematically showing the positions of the catheter and dilator. Fig. 7 is an cross-section oat the line VI1-NI1 in fig. 4 showing the dilator and guide- wire in proper positions. Fig. 8 is an sectional view like fig. 7 showing the catheter in the proper position. Fig. 9 is a side elevation of the device with dilator and guide- wire. Fig. 10 is a top elevation of the second design of the device of the present invention. Fig. l la-f show partly sectional views illustrating the procedure of using the device of the present invention for catheterization.

Figs. 1-9 show the device 1 of the present invention, consisting of a tubular member 2 and a head 3. The sheath is provided with a slot 4 extending from the distal end of the sheath towards the head, so that a groove or channel 5 is produced, defined by the inner wall of the sheath and open via the slot and forward, also connected to the central opening 6 of the head (fig 5). Fig. 4 shows how a catheter 7 is positioned in the sheath when accomplishing the technique according to the present invention. Note that the catheter 7 is not inserted through the opening of the head-member for reasons explained below.

Fig. 10 shows an alternative design of the device 1 of the present invention also consisting of a tubular member 8 and a head member 9 having a not indicated opening

extending all along the device through both end 10 and 11. At least the tubular member 8 in this design is made of a thin and flexible material having a narrow slit 12 extending from the proximal end 10 towards the head 9 terminating as a wide opening 13.

Figs. 6-8 show the correct positions of the sheath 2, catheter 7, a dilator 14 and guide- wire 15, in the first design of the present invention during different steps of the procedure of catherization according to the method of the present invention shown in (fig.

1-9).

As seen in the drawings the slot has preferably a width smaller than the inner diameter of the sheath (fig. 7) in order for the edges of it to grip around the dilator keeping it firmly within the sheath. Later, when the catheter is guided through the sheath, a "roof" is formed between these edges by the surrounding tissues preventing the catheter from escaping out of the sheath, so when advanced it will be guided into the vessel.

The procedure of catherization in accordance with the technique and device of the present invention may now be described with reference to particularly figs, l la-f. A central vein 16 is located with a syringe when administrating local anaesthetics. A small bore cannula is inserted into the vascular lumen with the guidance of the previously found position, whereupon the guide- wire 15 is advanced to the vessel 16 through the cannula to a radiographically verified position in the superior caval vein.

After removal of the cannula a small incision of the skin and an underlying subcutaneous "pocket" 17 is made. The catheter 7 and the port 18 are now connected if that has not been done at an earlier stage. The catheter 7 is cut to the proper length according to the radiografϊcal information. A skin incision with a length slightly greater than the diameter of the port is made just distal to the intended position of the port 18. By blunt dissection a subcutaneous pocket 19 with a width just barely accepting the port and a length permitting the latter to be is pushed in completely is formed.

The catheter 7 is tunnelled through the pocket to the place of the guide-wire 15 where the previously made 1 cm long pocket is made. Thus the catheter 7 and guide- wire 15 emerge into and out of the same opening. During this tunnelling manoeuvre the port 18 will be placed in its pocket 19 so that it barely disappears out of sight. Two ligatures 20 are put in fascia in the bottom of the distal end of the pocket and threaded through the posterior holes of the port just before it is pushed in.

The device according to the present invention with dilator 14 included is then passed over the guide- wire 15 into the vessel 16, the device with the tubular member 2 is pushed in whereupon the dilator is removed.

The catheter 7 with its length corrected earlier, is then inserted through the slot- -opening of the tubular member 2 and guided on as far as possible. Only a minimal portion of the catheter, possible kinked, is at this moment visible in the subcutaneous pocket at the puncture site. The device is now extracted, the catheter 7 being held in place with the slight pressure of a finger.

In order to minimize the risk of bleeding or aspiration of air, the dilator 14 is removed just prior to the insertion of the catheter 7 into the tubular member. It is understood

understood that the patient is positioned in such a way that a verified positive central venous pressure exists.

The ligatures (20) attaching the distal part of the port (18) to the surrounding tissues are tied, pulling it backwards somewhat during the procedure so that the catheter is tightened slightly and any eventual kink at the site of the proximal incision is stretched out. If the port does not move backwards any possible kinked loop will disappears after "massage". Finally the dermis and possibly the subcutis are sutured.

If the plastic sheath of a thinner material is being used the slit (12) with which it is provided will open itself when extracting the sheath, provided that the catheter is fixed with a finger at the moment of extraction hindering it from accompanying the sheath out.

An alternative to the use of a dilator, the device according to the invention can be placed on the outside of a relatively large-bore cannula, which it is introduced directly into the vessel whereupon the sheath is pushed in. The diameter of the cannula will then be equal to the inner diameter of the tubular member and somewhat larger than that of the catheter.

With the use of the device of the present invention all necessary connections can be made by the fabricator under optimum conditions. The length of the catheter can readily be corrected during the operation by cutting off the proximal part of the catheter, or simply by using a few prefabricated standard lengths.

The technique according to the present invention implies a simplification, increased safety and faster execution especially if subcutaneous tunnelling and implantation of port systems are made.

The device according to the present invention has a standardized head (3) at the distal end to which syringes or standardized attachments can be connected. Being "unbroken" it has maximum stability and even violently made connections cause no alteration to its shape.

Consequently, the head constitutes a firm foundation of the tubular member which, despite the opening, the slot or slit has an acceptable rigidity in the head end. This allows a width of the tubular opening and slot almost equal to the inner diameter of the sheath. Thus it is possible for the lateral introduction of a catheter, with a diameter almost equal to the diameter of the tubular inner lumen

The slot (5) has a width insignificantly exceeding the diameter of the catheter (7) in width, making extraction of the catheter possible with a minimum of force. As the catheter is inserted through the tubular member, the surrounding tissues form a defined roof preventing the catheter from escaping out through it.

The approximate inner diameter of the device may for instance be; inner tubular diameter 2 mm, length 85 mm. The outer tubular diameter of the tubular member 2.6 - 3 mm depending on the material, and the outer diameter of the catheter preferably 1.6 - 1.8 mm.

When the sheath is being extracted, the flexible catheter must not accompany it the least, not even parts of a cm, as this would result in a loop with the risk of kinking at the puncture site. The "unbroken" head and the slot constitutes a sheath with no mobile

parts, sufficient stability of form and a simple design making it uncomplicated to manufacture.

The device is thought to be used with a dilator 14, having an outer diameter equal to the inner diameter of the tubular member. The bevelled end of the dilator starts approximately 5 mm distal to the end of the tubular member. The end of the tubular member 10 is bevelled and forms a smooth transition between itself and the dilator 14 in order not to get caught in the wall of the vessel when the latter is penetrated.

The device according to the invention can be manufactured of either steel or plastic material so dimensioned that no or insignificant flexure exists. If a too thin material is used, the sheath 2 will be flexible to a degree at which the slot enlarges when bent or the tubular member gets squeezed by the surrounding tissues as the dilator is extracted .

The outer diameter of the dilator is preferably slightly less than the inner diameter of the tubular member in order to fit exactly inside the latter. The length of the dilator and cannula should preferably exceed that of the sheath by at least 50 and 15 mm respectively, and the guide-wire have a length that exceeds the sheath by at least 150 mm. The dimension of the soft catheter in relation to the device are; an outer diameter less than the width v of the slot and less than the height h of the channel, 75 - 80 % of the inner lumen diameter being the optimum.

The second design of the device according to the present invention replaces the wide slot described above with a narrow slit 12 in front of the opening 13 (fig. 10), the thin material of the tubular member makes extraction of it possible as the slit easily opens itself to the catheter. The slit makes the tubular member more stable than a slot. Notwithstanding the pressure of the surrounding tissue the inner lumen remains intact.

It is obvious that the present invention, having been presented in the above detailed description set forth in conjunction with the drawings, can be modified within the framework of the claims attached.