PROBLEMS IN THE MAINTENANCE OF V-A BYPASS

Abstract

We performed veno-arterial bypass (V-A Bypass) in eight patients for severe postoperative heart failure intractable with medical control and intra-aortic balloonn pumping (IABP). The average bypass time was 62 hours ranging from 2 to 261 hours and perfusion index ranged from 0.8 to 2.8L/min/m².The problems we met during V-A Bypass were 1) uncontrollable bleeding, 2) renal failure, 3) rupture of a pump tube and a membrane lung, 4) unstable hemodynamics. Bleeding was relevant to the mode of heparinization and it was better controlled with continuous administration of heparin at the dose of 5-7 units/kg/hour by keeping the activated coagulation time (ACT) around 200 seconds. For the control of the renal failure, hemodialysis with a unit incorporated in the bypass circuit was preferred to peritoneal dialysis in its efficacy. Rupture of a membrane lung was experienced with a Landé-Edwards' lung, but not with a Kolobow lung. The lifetime of a pump tube of Latex rubber was about three days and the one of more durability was expected. Hypothermia in the level of 32-34°C seemed to be effective in decreasing the oxygen consumption during V-A Bypass with the proper use of vasodilator.
No survival was obtained in this series with V-A Bypass. Many troubles we experienced with the present type of V-A Bypass may be solved when an assist heart device becomes available.