Minimal hemolytic effect of veno-venous bypass during liver transplantation

During liver transplantation, extracorporeal veno-venous bypass (VVBP) from the lower to the upper part of the body is used to prevent the negative circulatory effects otherwise seen on clamping the inferior caval vein during the actual change of livers. Extracorporeal circulation can sometimes be complicated by hemolysis. Therefore, we wanted to determine whether the technique used during liver transplantation might also cause hemolysis. This was measured as plasma hemoglobin using a spectrophotometric method including tetramethylbenzidine. Of 11 patients tested, 5 showed an increase in plasma hemoglobin during the use of VVBP; in no case, however, was this clinically significant. Three patients showed short peaks of hemoglobin during bypass. In two patients the rise continued after bypass and they required higher pump speed than the six patients without hemolysis (mean +/- SD 1900 +/- 150 RPM vs 1700 +/- 60 RPM, respectively). Pump flow, time of VVBP, and numbers of transfusions during the transplantation did not differ between the groups. We conclude that VVBP used during liver transplantation may cause hemolysis, but with low frequency and low clinical significance. We further conclude that the spectrophotometric method used is reliable and sensitive enough to determine the degree of hemolysis.