Extracorporeal Circulation in Liver Transplantation

______________ _ Extracorporeal circulation has recently expanded outside the realm of the traditional cardiac procedures. Extracorporeal circulation and cardiopulmonary bypass has expanded to include: left and right heart long and short term support, systemic and regional hyperthermic perfusion for cancer therapy, systemic rewarming for hypothermia victims due to exposure, repair of aortic tears and aneurysms, support for respiratory failure, and more recently involvement in support of the surgical process for liver transplantation. The first orthotopic liver graft was performed by Starzl and colleagues in 1963 at The University of Colorado at Denver. Then in 1982 Starzl began utilizing veno-veno extracorporeal circulation. Vena-arterial bypass has also been utilized in other centers. Presently, the use of extracorporeal circulation in liver transplantation is being implemented in an increasing number of centers. There have been a wide range of benefits with the use of extracorporeal circulation in liver transplantation. These benefits are the control of the systemic and perihepatic circulation, greater control of volume status through efficient rapid infusion systems and decreased morbidity and mortality. The increased confidence gained by the use of extracorporeal circulation, enables patients to be referred for transplant surgery at an earlier stage, with a more reasonable prospect for a successful surgery. Introduction _____________ _ The first orthotopic liver graft was performed by Starzl and colleagues in 1963 at The University of Direct communications to: Scott P. Garavet, PSICOR, Inc., 810 East Grand River, Brighton, MI 48116 Colorado at Denver. In the time between 1963 to 1980, liver transplantation did not gain acceptance or become established as a therapeutic procedure because the dangers of the surgical procedure appeared to be prohibitive. Cirrhotic patients tended to be referred for surgery in a terminal state with liver failure, portal hypertension, deranged electrolyte balance, renal failure, and toxic myocarditis manifested by hypotension. In review the liver has a very significant and wide range of functions. These functions include: 1) removes glucose from which it synthesizes glycogen, which it stores; 2) deaminizes amino acids turned into urea; 3) produces proteins such as albumen, prothrombin component and fibrinogen; 4) secretes bile; 5) synthesizes fibrinogen and prothrombin, blood constituents essential for clotting; 6) source of RBCs in the fetus; 7) filters out bacteria; 8) storage for vitamins; 9) regulates blood volume; and 10) important in lipid metabolism. It was only after a long period of experimentation that extracorporeal circulation for liver transplantation was introduced, in 1982, at Presbyterian University Hospital, Pittsburgh, Pennsylvania. The initial technique was the use of a vena-arterial system. The extracorporeal circuit consisted of a roller pump, cardiotomy reservoir, arterial blood filter, reservoir bag, and heat exchanger. The technique required total systemic heparinization (200j..t/kg). Pooled blood was returned to the circuit, through suction pump to the cardiotomy reservoir. When extracorporeal circulation was terminated, protamine was given to reverse the heparin. The results obtained included: elimination of pooling, reduction of hypertension in the venous beds, and the preload to the heart remained essentially unchanged. However useful extracorporeal circulation was in the early cases, the advantages were grossly outweighed by the inability to establish normal clotting times which resulted