Pulmonary metabolism of propofol during anhepatic phase of orthotopic liver transplantation in pigs

Abstract

Objective: Propofol is a widely used intravenous anesthetic agent which has a total body clearance exceeding hepatic blood flow which suggests extrahepatic metabolism. We therefore assessed the pulmonary metabolism of propofol during the anhepatic phase of orthotopic liver transplantation in pigs.Methods: Seven adult female pigs weighing 30.0±3.37 kg during anhepatic phase of orthotopic liver transplantation were studied. Intravenous anesthesia was induced with 3.5 mg/kg propofol and after endotracheal intubation, anesthesia was maintained with 15 mg/kg/h propofol and 1 pg/kg/min alfentanil infusion following a 10 pg/kg alfentanil bolus. Propofol concentrations from the pulmonary and carotid artery and propofol metabolites in the urine were measured by capillary gas chromatography before the anhepatic phase, every 15 minute during the anhepatic phase and at 30 minute intervals during reperfusion.Results: During the anhepatic phase, propofol concentrations in the pulmonary and carotid artery increased significantly (p<0.05) but propofol metabolites in urine did not change (p>0.05). Although propofol concentration in the pulmonary artery was higher than that of the carotid artery, the difference was not statistically significant. The mean extraction coefficient was 0.13.Conclusion: We conclude that propofol has low pulmonary extraction and other organs or tissues, such as gut wall, may be responsible for the extrahepatic metabolism of propofol.