Cannulation of blood vessels for prolonged hemodialysis *

In the process of trying to simplify the technique of continuous hemodialysis, the problem of long-term cannulation of arteries and veins presented itself. The technique which has been developed and is herein described solves this problem by making use of two devices. First, the cannulas are placed in the vessels through a subcutaneous tunnel so that they emerge from the skin through a tightfitting puncture wound some distance from the site of vessel cannulation. Second, a special fitting has been developed which permits the arterial cannula to be connected directly to the venous cannula thereby creating a small arterio-venous shunt which will stay open indefinitely during periods when dialysis is not in progress. This technique permits a single cannulation of vessels at the outset of treatment of acute renal failure. Dialysis may then be performed at any time simply by replacing the shunt with the hemodialyzer. No anticoagulation is required when the shunt is in place, and the risk of infection is minimized by the tunnel and puncture wound. This bypass technique has also been applied to the problem of long-term cannulation of patients with chronic renal disease. The technique of insertion is the same except that the tunnels are longer. The long tunnels are used to afford maximum protection against infection. These long tunnels are not used in the patients with acute renal failure because of the potential bleeding problem. In the patients with chronic renal failure a delay of several days before the initial dialysis permits healing. Such delay is not possible in patients with acute renal failure, hence the tunnel is made as short as possible to minimize the chance of bleeding. It is interesting that Alwall in 1949 used the bypass as a method of keeping the cannulas open, but stated that the patient must be heparinized, which was probably the case because glass tubing was used for the bypass. The teflon tubing used in our bypass has ideal characteristics to prevent clotting, and none has occurred in our first six cases. Figure 1A shows the bypass and arm plate in place on the arm of a patient with chronic renal failure. At the time the picture was taken the cannulas and fitting had been in place for four weeks. Figure 1B is the same view with the dressings removed (These and other figures mentioned in this article are available online at http://www.blackwellpublishing.com/ products/suppmat/HDI/HDI080/HDI080sm.htm). The cannula from the radial artery makes a 180 turn under the lower incision and emerges through the lower puncture wound. It then enters the lower Swagelok of the arm plate and its square cut end abuts tightly against the curved constricted teflon tube which is the bypass. The venous cannula also abuts tightly against the other end ot the bypass thus forming a smooth uninterrupted teflon tube. The venous cannula re-enters through the skin and curves around into a small forearm vein. The rate of blood flow through the bypass assembly is about 100–200ml. per minute depending on how much of a constriction is put in the bypass loop.