WO2007126380A1

WO2007126380A1 - Microdialysis catheter with fixating means

Info

Publication number: WO2007126380A1
Application number: PCT/SE2007/050282
Authority: WO
Inventors: Stefan Lindgren
Original assignee: Cma/Microdialysis Ab; Burman, Sven
Priority date: 2006-05-02
Filing date: 2007-04-27
Publication date: 2007-11-08

Abstract

The invention resides in A catheter adapted to be attached to organs or tissue, said catheter having an inlet and an outlet for perfusion liquid and dialysate, respectively, which at the proximal end of the catheter are joined in a mounting, an inner tube and a concentrically arranged outer tube operatively coupled to the mounting, said inner 5 tube and outer tube extending to the distal end of the catheter, said outer tube having a membrane arranged in surface of the outer tube adjacent to the distal end of the catheter said catheter having outer shaft (210;310;410) arranged concentrically with the outer tube (205;305;405), and that means for fixation of the catheter comprising at least one suture (209;309;409) is attached to the mounting (203;303;403), so as to 10 pass between outer tube (205;205;405) and the outer shaft (210; 310; 410).

Description

MICRODIALYSIS CATHETER WITH FIXATING MEANS

FIELD OF THE INVENTION

The present invention generally relates to a catheter according to the preamble of claim 1 , and especially to a microdialysis catheter, more specifically for use for diagnostic or testing purposes. It may be used in the body or an organ in order to perform various analyses of e.g. interstitial fluids etc. and the catheter may be temporarily fixated in place and thereafter withdrawn.

BACKGROUND OF THE INVENTION The meaning of specific wordings in the text for the purpose of this application should be interpreted as follows:

The word catheter should be interpreted also as probe.

Perfusion liquid is the liquid used in the microdialysis, which is allowed to enter the probe and there take up substances from the surrounding tissue through a membrane. The perfusion liquid becomes the dialysate after the dialysis.

The word shaft should be understood as being one or more concentric tubes arranged in the catheter.

The inlet and outlet of the catheter as described may in case of a reversed flow be used as outlet and inlet, respectively.

Microdialysis is used to monitor interstitial fluids and blood in various body organs.

The technique relies on the passage of a perfusion liquid through the catheter and the collection of the resulting dialysate, which is the result of the microdialysis having taken place through the membrane during the passage of the perfusion liquid through the catheter.

Microdialysis provides a method for in vivo sampling, during which little or no fluid is removed from or introduced into the system. It involves having the catheter located at a site for measurements, the catheter exhibiting a dialysis membrane at that site, thereafter continuously/discontinuously perfusing the interior of the membrane with a solution similar in composition to the body fluid at that site. The dialysate, containing substances which during the dialysis have diffused through the membrane, may easily be collected and analyzed. However, the perfusion liquid on entering the catheter may also contain substances which are supplied to the body/organ. The substance may e.g. be a pharmaceutical preparation, an isotope, or a substrate for an enzymatic reaction in the liver.

Microdialysis probes are by nature fragile and very small, which requires great care in inserting and withdrawing the probe from the tissue in which it is used. Probes are often made in the form of an inner and an outer tube, where the outer tube exhibits a membrane and the dialysate and the perfusate, is entering and exiting the tube at one end, and the other end of the tubes are fused or plugged. The rigid or flexible type cannula probe have, even though their geometries differ, relatively large diameters at the junction of their inlet and outlet tubing since they enter and exit a body at the same point. This type of probe is usually partly entered into brain tissue or some other tissue from the outside of the body, i. e. the liquid cross will be outside the tissue to be measured on, and thus has a limited available depth depending on the length of the probe, where the dialysis is to take place. This design also has limitations in the attachment and insertion of the probe to/in soft and/or moving tissue, e.g. skin, heart, liver, eye, and tumor in that the catheter should be fixated in place. The problem is discussed below in connection with a prior art catheter shown in Fig. 1

In Fig. 1 is shown a microdialysis catheter according to the prior art. Inlet and outlet ducts for perfusion liquid and dialysate 101 and 102 are shown entering a mounting 103, also described as a liquid cross. The mounting exhibits a grove 108, which is intended to use in combination with a suture 109 in order to fixate the catheter in the tissue of organ. The catheter further comprises an inner tube 104 arranged to reach essentially to the distal end 107 of the catheter. Concentrically with the inner tube

104 and outside the same an outer tube 105 is arranged. The outer tube 105 having a dialysis membrane 106, the membrane is preferably placed adjacent to the distal end 107 of the catheter. Preferably the dialysis membrane is fastened to the outer tube

105 using glue. Indicated at the 111 is the abdominal wall through which the catheter at a later stage will have to be withdrawn through. The problem which then arises is that the withdrawal will be made through a relatively small opening in e.g. the abdominal wall or any other tissue, by pulling essentially in the ducts 101 and 102 or using some other arrangement for pulling the catheter using the liquid cross.

To keep the catheter in place in order to make measurements in the same location throughout the procedure, the suture 109 fixated in the grove 108 is used to fasten the suture in a suitable ligament or the like. The suture is preferably of a reabsorb- able type. The man skilled in the art would know how to perform this. The catheter may then by pulling be loosened from the ligament and the withdrawal may be started. However, it has been shown that withdrawal has two moments which still present a problem, one when the liquid cross is withdrawn and the other is that the withdrawal itself puts compressive forces from tissue and tensile forces from pulling, etc. on the liquid-containing parts of the catheter i.e. the outer tube 105 and the inner tube 104. These forces are concentrated to the outer tube 105 and may propagate to the glued joint between the outer tube 105 and the membrane 106 and damage the same.

Further microdialysis probes are described in SE-C-434 214, US,A,5,735,832 and US,A,5,741,284. Further patents representing various devices for microdialysis are e.g. US 4,694832, US 5,106365, and US 6929618.

SUMMARY OF THE INVENTION The invention relates to a catheter adapted to be attached to organs or tissue, said catheter having an inlet and an outlet for perfusion liquid and dialysate, respectively, which at the proximal end of the catheter are joined in a mounting, an inner tube and a concentrically arranged outer tube operatively coupled to the mounting, said inner tube and outer tube extending to the distal end of the catheter, said outer tube having a membrane arranged in surface of the outer tube adjacent to the distal end of the catheter said catheter further having an outer shaft arranged concentrically with the outer tube, and means for fixation of the catheter comprising at least one suture attached to the mounting, so as to pass between outer tube and the outer shaft.

Preferably the mounting of the catheter according of the invention is the liquid cross.

Preferably the mounting exhibits fastening means for attaching the at least one suture to the same.

Preferably the outer shaft adjacent its distal end comprises fixating means for fixating the suture to the distal end of the outer shaft.

It is thus an object of the invention to provide a microdialysis probe, which is may be inserted both into more deeply located organs or in generally deeply located places for microdialysis, where the common type of catheter will be difficult to attach and remain attached during the microdialysis procedure.

It is thus a further object of the invention to provide a microdialysis catheter which may be inserted e.g. after a liver transplantation and where it may be secured safely in e.g. a ligament.

It is also an object of the invention to provide a microdialysis probe, which essentially may be left for a period in the measuring spot, e.g. in a transplanted liver, and thus allow monitoring of the liver postoperatively, truly reflecting the metabolic changes continuously. At an appropriate time after surgery, when the liver has been monitored for a needed period, the catheter should then so constructed as to allow complete removal with ease. To be able to leave the microdialysis catheter in the liver after operation allows for early detection of complications in the transplant and will allow the surgeon to re-operate and thus increases the chance to save the liver from complications such as thrombosis, cholangitis etc. It is pointed out, that although above is discussed a transplanted liver, the catheter may just as well be used before removal of the liver from the donator and also while waiting for the transplantation. The catheter may of course also be used in any other appropriate location as the liver is only used for exemplary purposes in this description.

The catheter should thus be removable fastened to the organ or tissue in which the catheter is placed. The catheter according to the invention is therefore supplied with a suture which is used for suturing the catheter to e.g. the falciform ligament at the liver. The invention is described as having one suture, however, the catheter could be provided with more than one suture.

A problem is how to attach the suture to the catheter safely. The suture needs to be attached such that there is no risk of leaving any part of the catheter in the wound

These objects according to the invention are solved by the catheter according to claim 1 and the subsequent subclaims in which:

The mounting exhibits fastening means for attaching the at least one suture (209;309;409) to the same.

The outer shaft adjacent its distal end comprises fixating means for fixating the suture to the distal end of the outer shaft.

A gold thread is arranged within the inner tube (204;304;404) at the distal end (207; 307; 407) of the inner tube in order to make the catheter observable using X-ray etc.

BRIEF DESCRIPTION OF THE DRAWINGS

The objects and advantages and features of the present invention will be more readily understood from the following detailed description of the preferred embodiments thereof, when considered in conjunction with the drawings, in which like reference numerals indicate identical structures throughout the several views, and wherein:

Fig. 1 shows a catheter according to prior art;

Fig. 2 shows a first embodiment of the catheter according to the invention. Fig. 3 shows a second embodiment of the catheter according to the invention. Fig. 4 shows a third embodiment of the catheter according to the invention.

DETAILED DESCRIPTION QF THE PREFERRED EMBODIMENTS OF THE INVENTION Fig. 1 has already been described above in connection with prior art.

In Fig. 2 is shown a microdialysis catheter according to one embodiment of the invention. Inlet and outlet ducts for perfusion liquid and dialysate 201 and 202 are shown entering a mounting 203, which may be identical to that which is termed a liquid cross. The catheter further comprises an inner tube 204 arranged to reach essentially to the distal end 207 of the catheter. Concentrically with the inner tube 204 and outside the same an outer tube 205 is arranged. The outer tube 205 having a dialysis membrane 206, and the membrane is preferably placed adjacent to the distal end 207 of the catheter. Indicated at the 211 is the abdominal wall through which the liquid bearing parts at a later stage will have to be withdrawn through. It should be noted that in this embodiment the liquid cross 203 will remain outside the abdominal wall 211 making for an easier removal of the catheter.

According to the invention a suture 209 is used also here in order to fixate the catheter in the measurement location. However, the suture is not fastened into a circumferential grove in the liquid cross as in the known art but fasten/fixated 208 in the liquid cross in such a manner that it will be protected. The withdrawal will thus not put the same compressive forces from tissue and tensile forces from pulling, etc. on the liquid-containing parts of the catheter i.e. the outer tube 205 and the inner tube 204. This is avoided according to the invention by arranging an outer shaft 210 concentrically with, and outside the outer tube 205.

The suture 209, as shown, is fixated in a fastening means 208 in the liquid cross/mounting 203 at a location between the outer tube 205 and the outer shaft 210, thereby protecting the outer tube 205, the inner tube 204 and the membrane from tensile and compressive forces as they will be taken up by the outer shaft 210. Exemplary measurements for a microdialysis catheter may be summarized as follows.

Material Length mm Diameter mm

Outer polyurethane 310 0,9 tubing

Outer shaft polyurethane 280 1,5

Membrane polyarylethersulphone, 30 0,6

PAES

Inlet tube polyurethane 400 1,0

Outlet tube polyurethane 70 1,0

Suture braided polyestersuture 200 out- sticking part

Further embodiments according to the invention are shown in Fig. 3 and 4 in which the catheter essentially only differs in how the suture is fixed to the catheter. Like reference numbers in Fig. 2, Fig. 3, and Fig. 4 denote the same details.

In Fig 3 is shown that the suture which is fixated in the mounting 303 by a fastening means 308 also is fixated at 313 by threading the suture through a hole in the wall of the outer shaft 310 creating a loop in the suture on exiting the interspace between the outer shaft 310 and the outer tube 305. The pulling and tensile forces will then essentially be taken up by the outer shaft while the rest of the catheter is protected.

In Fig 4 is shown that the suture which is fixated in the mounting 403 by a fastening means 408 also is fixated at 413 by a fixating means e.g. application of glue or the like 413 to the outer shaft 410. It is, however, important that the glue does not attach to the outer tube 405 as that would destroy the effect. The pulling forces will then essentially be taken up by the outer shaft while the rest of the catheter is protected.

Although the present invention has been described in connection with preferred embodiments thereof, it will be appreciated by those skilled in the art that additions, deletions, modifications and substitutions not specifically described may be made without departing from the spirit and scope of the invention as defined in the appended claims.

Claims

1. A catheter adapted to be attached to organs or tissue, said catheter having an inlet and an outlet for perfusion liquid and dialysate, respectively, which at the proximal end of the catheter are joined in a mounting, an inner tube and a concentrically arranged outer tube operatively coupled to the mounting, said inner tube and outer tube extending to the distal end of the catheter, said outer tube having a membrane arranged in surface of the outer tube adjacent to the distal end of the catheter characterized in that an outer shaft (210;310; 410) is arranged concentrically with the outer tube (205;305;405), and that means for fixation of the catheter comprising at least one suture (209;309;409) attached to the mounting (203;303; 403), so as to pass between outer tube (205;205;405) and the outer shaft (210; 310; 410).

2. A catheter according to claim 1 characterized in that the mounting (203;303; 403) is the liquid cross (203;303;403).

3. A catheter according to claim 1 or 2 characterized in that the mounting (203;303;403) exhibits fastening means (208,308,408) for attaching the at least one suture (209;309;409) to the same.

4. A catheter according to any of the preceding claims characterized in that the outer shaft (310; 410) adjacent its distal end comprises fixating means (313;413) for fixing the suture (309;409) to the distal end of the outer shaft.

5. A catheter according to any of the preceding claims characterized in that a gold thread is arranged within the inner tube of the distal end (207;307;407) of the inner tube (204; 304; 404).

6. A catheter according to any of the preceding claims, said catheter adapted to be arranged such that the liquid cross (203;203;403) resides outside the body during dialysis.