Effect of Sevoflurane Versus Isoflurane on Emergence Time and Postanesthesia Care Unit Length of Stay: An Alternating...

We previously reported that the duration of hospitalization was not different between isoflurane and sevoflurane. But more plausible consequences of using soluble volatile anesthetics are delayed emergence from anesthesia and prolonged stays in the postanesthesia care unit (PACU). We therefore compared isoflurane and sevoflurane on emergence time and PACU duration.

We reanalyzed data from 1498 adults who participated in a previous alternating intervention trial comparing isoflurane and sevoflurane. Patients, mostly having colorectal surgery, were assigned to either volatile anesthetic in 2-week blocks that alternated for half a year. Emergence time was defined as the time from minimum alveolar concentration fraction reaching 0.3 at the end of the procedure until patients left the operating room. PACU duration was defined from admission to the end of phase 1 recovery. Treatment effect was assessed using Cox proportional hazards regression, adjusted for imbalanced baseline variables.

A total of 674 patients were given isoflurane, and 824 sevoflurane. Emergence time was slightly longer for isoflurane with a median (quartiles) of 16 minutes (12-22 minutes) vs 14 minutes (11-19 minutes) for sevoflurane, with an adjusted hazard ratio of 0.81 (97.5% CI, 0.71-0.92; P < .001). Duration in the PACU did not differ, with a median (quartiles) of 2.6 hours (2.0-3.6 hours) for isoflurane and 2.6 hours (2.0-3.7 hours) hours for sevoflurane. The adjusted hazard ratio for PACU discharge time was 1.04 (97.5% CI, 0.91-1.18; P = .56).

Isoflurane prolonged emergence by only 2 minutes, which is not a clinically important amount, and did not prolong length of stay in the PACU. The more soluble and much less-expensive anesthetic isoflurane thus seems to be a reasonable alternative to sevoflurane.