Shunt flow and caval pressure gradient during veno-venous bypass in human orthotopic liver transplantation.

The routine use of veno-venous bypass during the anhepatic phase of orthotopic liver transplantation is controversial. Decreased shunt flows (1.5-3.0 litre min-1), as reported in the literature, may explain the lack of beneficial effects on outcome. We have studied the influence of bypass flows on caval pressure gradient (CPG) and renal perfusion pressure (RPP) in 45 patients undergoing orthotopic liver transplantation using a portofemoro-subclavian veno-venous bypass system. Mean shunt flow was 3.63 litre min-1. Second-order polynomial regressions best described the relationship between shunt flow and CPG (r = 0.674), RPP (r = 0.727), and cardiac output (r = 0.602). Shunt flows less than 3.0 litre min-1 failed to normalize CPG and RPP, whereas flows greater than 5.0 litre min-1 did not substantially improve haemodynamic state.