WO1999002209A1

WO1999002209A1 - Two lumen cannula

Info

Publication number: WO1999002209A1
Application number: PCT/EP1998/004246
Authority: WO
Inventors: Josef Magasi
Original assignee: Süddeutsche Feinmechanik GmbH
Priority date: 1997-07-08
Filing date: 1998-07-08
Publication date: 1999-01-21
Also published as: DE19729022C2; DE19729022A1; PL338044A1; AU8974198A; JP2001509425A; EP0996475A1; BR9810690A

Abstract

The invention relates to a two lumen cannula (1) comprising an external cannula (2) designed as a perforation and incision cannula, and an internal cannula (3) which can slide in the external cannula and which, in a forward position, sticks out of the latter. These two cannulas (2, 3) are both bound to a respective blood hose (4, 5). The inventive two lumen cannula must be designed so that blood recirculation and blood vessels damage are avoided to a large extent. This is achieved by means of the internal cannula (3) being a flexible plastic cannula which, when in a forward position, sticks out so much with its forward end (6) of the external cannula (2) that no substantial recirculation of the blood can take place.

Description

description

Double lumen cannula

The invention relates to a double-lumen cannula with an outer cannula, which is designed as a stab incision cannula, and an inner cannula which can be displaced therein and which, in its forward position, projects beyond the outer cannula, and with two blood tubes, each of which is connected to one of the cannulas.

Double-lumen cannulas are used in the field of plasmapheresis or dialysis, i.e. when drawing blood and replacing parts with suitable solutions or in the artificial blood purification of kidney patients. In most cases, a permanent vascular access was created to draw and supply the blood by connecting an artery to a vein. This vascular access is called a shunt or fistula. Fresh arterial blood flows through the Nene and develops into a highly developed vessel that is easy to puncture. The puncture was typically carried out by means of two puncture cannulas, an arterial stab incision cannula further away from the body being used for taking the blood and a venous stab incision cannula closer to the body for supplying the cleaned blood.

The problem, however, is that dialysis patients have to clean their blood three times a week, with two puncture incision needles having to be applied each time using the conventional method. This is six punctures a week. This leads to the patient's vein being used up after a long period of treatment and therefore no longer being punctured. Therefore, ways were sought to extend the life of the shunt. One suggestion was to apply only a stab incision cannula that leads to branching. From this branch, two blood tubes with the interposition of blood pumps led to the dialysis machine. Blood was taken alternately and purified blood fed. With this method, the advantage that only one incision needle had to be applied was purchased with a number of disadvantages: the dialysis time doubled or the performance of the pumps had to be increased. However, the latter is harmful to the blood vessel, since the vein can collapse if the suction is too strong and damage to the vein wall, such as tears of the vein inner skin, can occur. Such damage can lead to Zeil growths that close the vein and make the shunt unusable. Further disadvantages were that part of the blood remains in the tube system (compliance), some of the cleaned blood is pumped into the arterial blood tube (pendulum blood) and some of the cleaned blood is removed again when switching to suctioning the cannula and the vein and in again is sent to the extracorporeal circuit (recirculation).

To avoid these disadvantages as possible ^'double lumen cannulas have been proposed. A double lumen cannula of the type mentioned at the outset is known, in which both cannulas are made of steel. The outer cannula is equipped with a T-shaped housing, the arterial blood tube being connected to the base of the "T", the cannula tip being located at one end of the "T" and the other end being tubular. The inner cannula can be inserted into this tubular end. It can be displaced in the tubular part in such a way that the front end of the inner cannula projects beyond the cannula tip or that it is withdrawn behind the cannula tip. The double lumen cannula is applied in the latter position. The inner cannula is then pushed into its front position. The arterial blood is withdrawn through the outer cannula and the purified blood (venous blood flow) is returned through the inner cannula. The inner cannula protrudes only a short distance from the outer cannula, which is due to the fact that such a steel part cannot be pushed further into the blood vessel without significantly increasing the risk of injury and the stress on the inner vein skin.

Although these and similar double lumen cannulas were able to overcome some of the problems mentioned above, the recirculation cannot be eliminated by this. This resulted from the fact that the rigid steel inner cannula can only be inserted a short distance into the vein and therefore the distance between the end of the inner cannula and the end of the outer cannula is relatively small. In this way, the arterial lie The sampling point and the venous return point are not far enough apart. This results in the removal of purified blood, i.e. recirculation, which makes dialysis ineffective and extends the treatment time. In practice, the recirculation is 10 to 30%. In addition, the steel front edge of the inner cannula placed at the front end carries the risk of damage to the inner vein wall. A further disadvantage is that emerge in the insertion of the inner cannula into the T-shaped housing blood and can reach to ekehrtem ^g path contaminants in the blood.

DE 195 35 349 A1 relates to a double-flow cannula for the treatment of gums and gums, with a washing-up liquid emerging from a rinsing cannula and being taken up again by a suction cannula surrounding it. The irrigation and suction cannula are made in particular of stainless steel.

DE 33 27 585 AI is a surgical instrument for epidural and spinal anesthesia and consists of a cannula with two needles lying one inside the other. In order to rule out injury to body tissue when inserting the needles, the needles are oriented to one another to the desired extent.

An infusion cannula is described in the literature reference "Die Braunüle", company lettering from Braun Melsungen, 2nd revised and supplemented edition, Nov. 1994, in which an outer plastic cannula surrounds a metal cannula running in it. The inner cannula must be removed to infuse.

The invention is therefore based on the problem of developing a double-lumen cannula of the type mentioned in such a way that the recirculation of the blood or blood and solution and vascular damage are largely avoided.

The object is achieved according to the invention essentially in that the inner cannula is designed as a flexible plastic cannula, which in its front position projects so far with its front end that the outer cannula no longer has any medically significant recirculation of blood. The invention was based on the knowledge that the arterial sampling point must be further away from the venous return point without the inner wall of the vein being stressed by the front edge of a metal tube. To solve this problem, the invention proposes forming the inner cannula from flexible plastic. It is thereby achieved that the inner cannula can be pushed much further into the vein, since it is not rigid, but also "seeks" the path through a curvature of the vein. The leading edge of this flexible plastic tube also poses a much lower risk for the inner wall of the vein, since the material is softer and because this inner cannula evades by its flexibility when it hits the inner wall of the vein. This allows the inner cannula with its front end to be pushed far enough into the vein that it projects a large distance beyond the front end of the outer cannula. The distance between the arterial sampling point and the venous return point can be measured in such a way that no significant recirculation of blood takes place.

A further development of the invention provides that the double-lumen cannula has a cannula housing that forms an absolutely closed system with the blood tubes. In this way, no blood can escape in the region of the double-lumen cannula, and no contamination can get into the blood.

There are various ways of ensuring that the inner cannula can be moved in the closed system. A further development provides that the rear end of the inner cannula has a piston-like rim which is mounted in a cylindrical recess of the cannula housing through which blood flows back so that the back-flowing blood pushes the inner cannula forward. The advantage of this embodiment is that the inner cannula is gently inserted into the vein with its front end and comes to a standstill if there is any resistance. If this is observed, for example, through a transparent housing, the inner cannula can be gently guided past the obstacle by a slight movement of the double-lumen cannula. A further embodiment provides that the rear end of the inner cannula has a thickening which is mounted within a flexible wall. It is then expediently provided that the thickening is held within the flexible wall in such a way that the inner cannula can be displaced by action from outside, but not by the blood flowing back. In this way, the position of the inner cannula can be adjusted as desired. The respective conditions, for example a curvature in the vein, can then be taken into account. The flexible wall can be the blood tube itself. Of course, other possibilities are also conceivable, for example that the thickening contains an iron core, as a result of which the inner cannula can be moved from the outside by means of a magnet.

The cannula housing of all embodiments can be equipped with a handle, for example with a turning handle, which allows the double-lumen cannula to be rotated and fixed in any position on the skin.

In order to be able to manufacture the cannula housing better, it can be provided that it consists of a front cannula housing and a branching piece, which are connected to one another by a coupling or in some other way. The cannula housing can at least partially consist of transparent material in order to be able to better observe the positioning of the inner cannulas and the blood flow.

Further details, advantages and features of the invention result not only from the claims, the features to be extracted from them - individually and / or in combination - but also from the following description of a preferred exemplary embodiment which can be seen from the drawing.

Show it:

1 shows a first example of a double lumen cannula according to the invention,

1 a and 1 b details of the double lumen cannula of FIG. 2, Fig. 2 shows another embodiment of a double-lumen cannula and

Fig. 3 an application to a vein.

1 shows a first exemplary embodiment of a double-lumen cannula 1 with an outer cannula 2 and an inner cannula 3. The outer cannula 2 is fixedly connected to the cannula housing 7, and the inner cannula 3 is displaceably mounted in this and in the outer cannula 2. The lumen 18 of the inner cannula 3 is used for the return of cleaned, ie venous blood, and the lumen 17, which is located between the outer wall of the inner cannula 3 and the inner wall of the outer cannula 2, is used to withdraw arterial blood. In the cannula housing 7 there is a fork through which the lumen 17 is connected to a blood tube 4 for the arterial blood and the lumen 18 to a blood tube 5 for the venous blood. The blood tubes 4 and 5 are only shown in FIG. 2, FIG. 1 only shows the connections 28 for the blood tubes, which are connected to a channel 19 for arterial blood and a channel 20 for venous blood.

The tip of the double-lumen cannula 1 is shown in FIG. 1b, the illustration showing the removal position as explained in FIG. 3 with the aid of an application to a vein 23. This front position of the inner cannula 3 shown in FIG. 1b corresponds to the position shown in FIG. 1. The rear position of the inner cannula 3 is shown with broken lines, in which its front end 6 lies within the outer cannula 2 and which serves to insert the vein 23 into the vein 23. Once this puncture has taken place, the inner cannula 3 must be moved to the front so that the arterial removal site 26 is far enough from the venous return site 27. In the exemplary embodiment shown, this displacement is served by the piston-like edge 8, which is located within a cylindrical recess 9 of the cannula housing 7. The rear part of the inner cannula 3 is drawn out in Fig.la. The inner cannula 3 is displaced by means of the piston-like rim 8 by the blood flow of the venous blood in the direction of the arrow 21. As a result, the inner cannula 3 is gently pushed into the vein 25.

The puncture tip 16 of the outer cannula 2 is ground in a conventional manner such that the Double lumen cannula 1 can be inserted into the vein 23 with as little injury as possible.

In the exemplary embodiment shown, the cannula housing 7 consists of a front cannula housing 13 and a branching piece 14 which are connected to one another by means of a coupling 15. In this way, the cannula housing 7 can be produced by means of, for example, simpler injection molded parts. In the front part of the cannula housing 7, a handle anchor 12 is provided, on which a handle, for example a rotary handle, can be attached.

FIG. 2 shows a further exemplary embodiment of the double-lumen cannula 1. In this exemplary embodiment, the inner cannula 3 has a thickening 10, which is located within a flexible wall 11, which in the exemplary embodiment is designed as a wall of the blood tube 5. The thickening 10 has such a dimension with respect to the flexible wall 11 that the thickening 10 can be displaced from the outside by finger pressure, but not by the blood flow. In this way it is possible to bring the inner cannula 3 consciously and specifically into a certain desired position. As a result, conditions such as the curvature of the vein can be taken into account, for example by stopping the displacement of the inner cannula 3 in view of an obstacle and only continuing when the obstacle can be avoided by changing the position of the double-lumen cannula 1.

3 shows the application to a vein 23. The double-lumen cannula 1 was applied by means of the puncture tip 16 into the vein 23 at the puncture 24. The inner cannula 3 was then moved forward, as described, so that the venous return site 27 is far enough from the arterial removal site 26. The distance must be such that the venous blood shown by arrow 21 can no longer reach the arterial blood shown by arrow 22, since distance and blood flow 25 no longer allow this. In this way, the dialysis can be carried out by means of a single puncture 24 with simultaneous blood withdrawal and blood return without any appreciable recirculation of blood. In this way, the patient's blood vessel is spared as much as possible, since only a single puncture 24 has to be made, the inner cannula 3 is inserted gently and through preventing blood recirculation the time of dialysis can be kept short.

Preferred dimensions of the double-lumen cannula, the inner cannula of which can be made of polyurethane or polytetrafluoroethylene (Teflon ®) or other materials suitable for indwelling cannulas and whose outer cannula can be made of steel such as AISI 304 or those according to DIN 1.4301, are:

Inner diameter of inner cannula: 0.5-1.5 mm, preferably approximately 1 mm, outer diameter of inner cannula: 0.6-1.6 mm, preferably 1.2 mm, inner diameter of outer cannula: 0.7-2.4 mm , Outer diameter outer cannula: up to 2.5 mm, preferably about 1.8 mm.

The distance between the tips of the inner and outer cannula when the double lumen cannula is applied, i.e. when blood is drawn and supplied, should be about 5 - 30 mm, in particular 15 mm with a blood flow of about 350 ml / min and a blood pressure of 200 mmHg.

Claims

Claims Double lumen cannula

1.Double-lumen cannula (1) with an outer cannula (2), which is designed as a stab incision cannula, and an inner cannula (3) which can be moved in it and which projects beyond the outer cannula (2) in its front position, as well as with two blood tubes (4 , 5), each of which is connected to one of the cannulas (2, 3), characterized in that the inner cannula (3) is designed as a flexible plastic cannula which, in its front position, has the front end (6) of the outer cannula ( 2) towered so far that no medically significant recirculation of blood takes place.

2. Double lumen cannula according to claim 1, characterized in that the double lumen cannula has a cannula housing (7) which form an absolutely closed system with the blood tubes (4, 5).

3. Double-lumen cannula according to claim 1 or 2, characterized in that the rear end of the inner cannula (3) has a piston-like edge (8) which is mounted in a cylinder-like recess (9) of the cannula housing (7) through which blood flows back is that the blood flowing back pushes the inner cannula (3) forward.

4. Double lumen cannula according to at least one of the preceding claims, characterized in that the rear end of the inner cannula (3) has a thickening (10) which is mounted within a flexible wall (11).

5. Double lumen cannula according to at least one of the preceding claims, characterized in that the thickening (9) is held within the flexible wall (10) in such a way that the inner cannula (3) can be displaced by action from the outside, but not by the refluxing blood is.

6. Double lumen cannula according to at least one of the preceding claims, characterized in that the flexible wall (10) is the blood tube (5).

7. Double lumen cannula according to at least one of the preceding claims, characterized in that the cannula housing (6) is equipped with a handle.

8. Double lumen cannula according to at least one of the preceding claims, characterized in that the handle is a rotary handle.

9. Double lumen cannula according to at least one of the preceding claims, characterized in that the cannula housing (7) consists of a front cannula housing (13) and a branching piece (14).

10. Double lumen cannula according to at least one of the preceding claims, characterized in that the cannula housing (7) consists at least partially of transparent material.

11. Double lumen cannula according to at least claim 5, characterized in that the thickening (9) consists of ferromagnetic material, which acts on a magnet for displacement.

12. Double lumen cannula according to at least one of the preceding claims, characterized in that the inner cannula (3) has an inner diameter of approximately 05 to 1.5 mm and an outer diameter of approximately 0.6 to 1.6 mm and / or the outer Cannula (2) has an inside diameter of about 0.7 to 2.4 mm and or an outside diameter of up to about 2.5 mm.

13. Double lumen cannula according to at least one of the preceding claims, characterized in that the inner cannula (3) consists of polyurethane or polytetrafluoroethylene and / or the outer cannula (2) consists of steel.