Carboxyhemoglobin concentrations during desflurane and isoflurane closed-circuit anesthesia

Desflurane has been implicated in carbon monoxide (CO) intoxication during general anesthesia under certain circumstances. Carboxyhemoglobin (COHb) concentrations were determined in forty-one patients who were randomly allocated to receive closed-circuit anesthesia (CCA) with 1.3 MAC of desflurane (n = 21) or isoflurane (n = 20) in oxygen. Soda lime was used to bind the produced CO2 in previous anesthetic procedures with fresh gas flows of < 21/min. In the desflurane group, COHb concentrations (mean +/- SD) were 0.86 +/- 1.15% and 0.81 +/- 1.11% before and after 1 h of anesthesia, respectively. In the isoflurane group, COHb concentrations were 1.15 +/- 1.47% and 1.19 +/- 1.39% before and after 1 h of anesthesia, respectively. COHb concentrations did not increase after 2 h of CCA in seven patients. Our data suggest that closed-circuit anesthesia with desflurane or isoflurane does not produce clinically significant increases in COHb concentrations under conditions that allow the soda lime to remain sufficiently wet.