The independent effect of propofol anesthesia on whole body protein metabolism in humans

Abstract

Background: The purpose of this study was to examine the effect of general anesthesia with propofol in the absence of surgical stimulation on whole body protein metabolism. Methods: Six unpremedicated patients were studied. General anesthesia included propofol (120 μg · kg-1 · min-1), vecuronium bromide, and oxygen-enriched air. Changes in protein breakdown, protein oxidation, and synthesis were measured by an isotope dilution technique using a constant infusion of the stable isotope tracer L- [1-13C]leucine (0.008 mg · kg-1 · min-1) before and during 100 min of propofol anesthesia. The plasma concentrations of glucose, lactate, non- esterified fatty acids, and cortisol were measured before and during anesthesia. Results: An isotopic steady state of plasma [1-13C]α- ketoisocaproate (taken to represent the intracellular leucine precursor pool enrichment for protein synthesis) and expired 13C-carbon dioxide were obtained before and during propofol infusion. Whole body protein breakdown decreased during propofol anesthesia by 6% (P < 0.05), whereas protein synthesis and oxidation did not change significantly. Plasma concentration of cortisol decreased after 90 min of propofol anesthesia (P < 0.05). No significant changes of plasma concentrations of glucose, lactate, and non- esterified fatty acids occurred during propofol administration. Conclusions: Propofol anesthesia did not significantly affect whole body protein synthesis and oxidation but caused a small, although significant, decrease in whole body protein breakdown, possibly mediated through the suppression of plasma cortisol concentration.