Background: Extrahepatic clearance of propofol has been suggested because its total body clearance exceeds hepatic blood flow. However, it remains uncertain which organs are involved in the extrahepatic clearance of propofol. In vitro studies suggest that the kidneys contribute to the clearance of this drug. The purpose of this study was to confirm whether human kidneys participate in propofol disposition in vivo.
Methods: Ten patients scheduled to undergo nephrectomy were enrolled in this study. Renal blood flow was measured using para-aminohippurate. Anesthesia was induced with vecuronium (0.1 mg/kg) and propofol (2 mg/kg) and then maintained with nitrous oxide (60%), sevoflurane (1 approximately 2%) in oxygen, and an infusion of propofol (2 mg . kg . h). Radial arterial blood for propofol and para-aminohippurate analysis was collected from a cannula inserted in the radial artery. The renal venous sample and the radial arterial sample were obtained at the same time after the steady state of propofol was established.
Results: The renal extraction ratio of propofol was 0.58 +/- 0.15 (mean +/- SD). The renal clearance of propofol was 0.41 +/- 0.15 l/min (mean +/- SD), or 27 +/- 9.9% (mean +/- SD) of total body clearance.
Conclusion: Human kidneys play an important role in the elimination of propofol.