A lower solubility recommends the use of desflurane more than isoflurane, halothane, and enflurane under low-flow conditions

Study Objective: To determine whether the lower solubility of desflurane, over that of isoflurane, enflurane, and halothane, favors its use in low-flow anesthesia. Design: Prospective clinical study. Setting: Technical University of Munich. Patients: 40 elderly (265 yrs), ASA physical status 11 and III surgical patients. Interventions: All patients were anesthetized and received delivered concentrations (FD) of 4 % desflurane, 1.5% isoflurane, 1.8% enflurane, or 0.9% halothane (n = IO patients for each anesthetic) in afresh gas inflow of 3 Llmin (high-flow), until end-tidal target concentrations (FR) of 2% d es fl urane, 0.5% isoflurane, 0.6% enflurane, and 0.3 % halothane were obtained. After 30 minutes., the inflow was decreased to 1 Llmin (low-flow), and the F, and the inspired concentration (FJ were adjusted to maintain the target concentration. Measurements and Main Results: The concentrations of the halogenated anesthetics, as well as nitrous oxide, oxygen (O,), and carbon dioxide, were measured in delivered gas at the common gas outlet and at the endotracheal tube connector. Transcutaneous 0, saturation, noninvasive blood pressure, and heart rate were also measured. During the first 30 minutes of high-flow administration, the target concentration was attained sooner with desflurane than with isoflurane, enjlurane, or halothane (median levels: 4 min vs. 6 min, 8 min, or 10 min; p < 0.01). After the reduction of inflow to 1 Llmin, FD had to be materially increased to maintain FI and F, for the more soluble anesthetics, but not for desflurane. Conclusions: At low flows, F, provides a reasonable surrogate of F, and FA for desflurane, but not for isoflurune, enflurane, or halothane. The rapid and predictable titrability of desflurane favors its safe use in low-flow technique.