This study defines some characteristics of a standard anesthetic circuit that may impede anesthetic induction and recovery with 1–653, sevoflurane, isoflurane, and halothane. Partition coefficients for anesthetic circuit components (masks, bellows, bags, airways, and circuit tubes) consistently ranked halothane > isoflurane > sevoflurane > I-653, suggesting a reverse order of washin and washout rates for an anesthetic circuit constructed from similar components. Consistent with this prediction, the concentrations of I-653 increased and decreased more rapidly than those of the other agents at any flow rate during wash in (0.5, 1, or 2 L/min gas inflow rates) or washout (1, 3, or 5 L/min) in a conventional anesthetic circuit. The rates of change in 1–653 concentration closely approximated the maximal possible theoretical rates. Our results suggest that absorption of 1–653 by circuit components or soda lime should not hinder induction of or recovery from anesthesia.
Address correspondence to Dr. Eger, Department of Anesthesia, University of California, Room S-455, San Francisco, CA 94143–0464.
© 1989 International Anesthesia Research Society