Metabolism of remifentanil during liver transplantation

We have investigated the pharmacokinetics of remifentanil and its less pote nt metabolite, GR90291, in six adult patients undergoing orthotopic liver t ransplantation (OLT). A single bolus infusion of remifentanil 10 mu g kg(-1 ) min(-1) was given at the beginning of the dissection and anhepatic phases of OLT. Remifentanil and GR90291 concentrations were measured in subsequen t serial arterial and mixed venous blood samples. Mean arterial clearance o f remifentanil was significantly greater (P=0.02) in the dissection phase ( 79.54 mi min(-1) kg(-1)) than in the anhepatic phase (39.57 mi min(-1) kg(- 1)). Steady state volumes of distribution were not significantly different. Clearance of remifentanil during the anhepatic phase was similar to that o f healthy adult patients. Mean maximum concentration (C(p)max) of GR90291 w as lower in the dissection phase than in the anhepatic phase (P=0.026). The re was no significant pulmonary metabolism of remifentanil.