Surgery – Devices transferring fluids from within one area of body to...
Reexamination Certificate
1998-11-06
2001-07-17
McDermott, Corrine (Department: 3738)
Surgery
Devices transferring fluids from within one area of body to...
C604S006160, C604S175000, C606S158000
Reexamination Certificate
active
06261255
ABSTRACT:
BACKGROUND OF THE INVENTION
1.Field of the Invention
The invention relates generally to an apparatus that facilitates vascular access for patients. In particular, the invention relates to an extended use tubing apparatus that is inserted into a patient to facilitate vascular access for chronic hemodialysis treatment. The tubing provides an arteriovenous fistula that resists occlusion and/or clogging.
2. Known Art
Over 130,000 patients undergo chronic hemodialysis in the United States each year as treatment for renal failure. Conventional hemodialysis treatment requires extensive and often extended, long-term vascular access. Access to the blood supply is generally sought through the vasculature, which is usually accomplished by establishing a native artery to vein arteriovenous fistula or by placement of a prosthetic graft fistula.
The Brescia-Cimino direct radio-cephalic fistula is a preferred form of permanent access to the vasculature. In this surgery, and in other native arteriovenous fistulas a communication is established between an artery traversing a limb (i.e. the arm or leg) and a corresponding vein in the same limb. If acceptable vasculature is not available then a prosthetic graft is employed to create a fistula for vascular access. Unfortunately, all types of vascular access are known to have a high failure rates and associated high costs of treatment. Vascular access often eventually fail due to the formation of scar tissue inside the vessel or due to vessel occlusion. Other common causes of graft failure are technique errors, infection, and neointimal hyperplasia at the distal anastomosis (venous) and within polytetraflouroethylene (PTFE) graft segments. Hyperplasia or buildup of fibrin at the venous anastomosis is probably the leading threat to most A-V fistulas. Arterial occlusive problems are less commonly the primary cause of fistula failure. As will be readily appreciated by those skilled in the art, failure of hemodialysis access contributes to morbidity, hospitalization time, and the cost of treatment.
While percutaneous interventional techniques (such as angoiplasty, atherectomy, and stent placement) are becoming increasingly popular in the management of hemodialysis access graft complications, these techniques are also generally prone to failure for the same reasons as the original fistula, necessitating further surgical revision. Such revision usually consists of the implanting of a PTFE interposition graft, and offer 30-day patencies of about 44-65%.
PTFE interposition grafts are also often placed in patients who have failed native fistula. Usually, these fistulae retain a small segment of patent vein beyond the anastomosis, and have reconstitution of veins further up the arm via collaterals. An interposition prosthetic graft is used to bridge the artery and vein.
Various types of highly flexible, non-porous tubings have been previously proposed for various medical applications. These applications typically involve the insertion of the tubing into a living body, either temporarily or as a permanent implant. Temporary applications include the use of the tubing as a catheter tubing to convey fluids into or out of a body, or alternatively as the tubing portion of a medical device such as an endoscope. For example, present endoscope channel tubes are made of porous expanded PTFE having a microstructure of nodes interconnected by fibrils, made as taught by U.S. Pat. Nos. 4,187,390 and 3,953,566.
These tubes typically have a very small pore size with a fibril length of less than five microns. They are quite flexible, inert, biocompatible and lubricious. However, due to the porosity of the tubing, during use various contaminants such as proteins and calcium tend to penetrate the void spaces present on the inner surface of the tube and to adhere to the inner surface. The adhesion of contaminants to the inner surface of the tube result in a decline in the slip properties of the inner surface, and also impaired other tube functions such as its flexing properties. Moreover, washing and sterilization were necessary in order to remove the contaminants so that the tube could be reused and such washing and sterilization were time consuming, and represented a burdensome operation.
Thus, there exists a need in the art for an improved apparatus for establishing reliable, long-term access to a patient's vasculature for chronic hemodialysis treatment. In particular, there exists a need for a fistula that facilitates subsequent remedial revisions including the removal and/or replacement of portions of the tubing. An ideal tubing should promote uninhibited blood flow through the tubing while resisting clogging or other occlusions.
SUMMARY OF THE INVENTION
The present invention addresses the problems associated with the known art. The invention includes a composite tubing graft with at least two conjoined sections. The first section includes an elongated tubing formed from PTFE, silicone, fluorosilicone or another catheter material that is similarly amenable for convenient arteriovenous access. The second section includes an elongated tubing formed from silicone or another suitable long-term catheter material. An intermediate connection couples the first section to the second section.
The first segment (i.e. the PTFE segment) is commercially available in varying lengths or rolls. The preferred diameters for the first segment are from between two millimeters to ten millimeters. The second segment (i.e. the silicone segment) is also commercially available in varying lengths. Ideally, the segment has a diameter of four to eight millimeters at the coupling site and tapers to approximately three to four millimeters distally. In an exemplary embodiment, the segment includes a radio-opaque strip proximate the terminus. While various connectors are suitable for use with the invention (including conventional luer fittings and the like), the selected connector must not inhibit blood flow, must be entirely extraluminal, and must provide for subsequent interchangeability of the first and second segments.
A method of inserting the apparatus into the venous system without an anastomosis to reduce graft failures compared to current methods also enables the tubing graft to be advantageously deployed in many patients. A significant advantage of the insertion method for the tubing graft is that the surgeon may avoid anchoring the second section in the venous system without a venous anastomosis. Consequently, the second section will have a freely moving venous end that resists clogging. (In percutaneously placed temporary venous catheters, it has been suggested that it is the free mobility of the catheter tip which is important in preventing and/or reducing clogging.)
The method for inserting the graft is as follows. Anatomic sites are selected and evaluated. Then, surgical antisepsis is achieved. The appropriate length and diameter composite graft is chosen according to the size of the selected artery and vein and distances therebetween. The distal end of the PTFE segment is sutured to a functioning artery using standard vascular techniques including systemic heparinization. Arterial inflow is assured. The appropriate vein is located and controlled with vascular tapes. The PTFE segment is tunneled subcutaneously close to the level of the vein. A venotomy is made and the silicone segment of the graft is inserted into the vein. An intraluminal trocar can assist with this insertion. The trocar is removed and venous back bleeding noted. In an alternate technique, the silicone segment (venous limb) can be inserted into a more proximal or central vein with standard peel-away technique. After insertion into the central vein, the distal silicone segment is tunneled subcutaneously to meet with the PTFE segment. The two segments are conjoined and flow established across the fistula. Adequate flow is determined with palpation for thrill and auscultation for bruit.
The invention also addresses problems related to PTFE intimal buildup by providing for subsequent graft cleaning that does not necessi
McNair William R.
Mullis Ronald Jay
Head Johnson & Kachigian
Koh Choon P.
McDermott Corrine
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