SEVOFLURANE VERSUS ISOFLURANE - INDUCTION AND RECOVERY CHARACTERISTICS WITH SINGLE-BREATH INHALED INDUCTIONS OF ANESTHESIA

Because of its nonpungent odor and low blood-gas solubility coefficien t, sevoflurane might be an ideal drug for single-breath inhaled induct ion of anesthesia. Fifty ASA grade I-III ambulatory surgical patients (18-76 yr old) received a single-breath induction with either 5.0% sev oflurane or 5.0% isoflurane (randomized) in a 1:1 N2O/O-2 mixture. Ane sthesia was maintained with the same anesthetic in 70% N2O until the e nd of surgery, when anesthetics were abruptly discontinued. Induction times (loss of eyelash reflex) were similar for sevoflurane (75 +/- 3 s, (x) over bar +/- se) and isoflurane (67 +/- 4 s, P = not significan t). Sevoflurane patients were less likely to have complications during induction (P < 0.005); coughing occurred more frequently with isoflur ane (P < 0.001). During induction, heart rate increased with both sevo flurane (from 73 +/- 3 to 90 +/- 4 bpm, P < 0.05) and isoflurane (from 70 +/- 2 to 92 +/- 2 bpm, P < 0.05); the increase with isoflurane was greater than that with sevoflurane. Times to eye opening for sevoflur ane (8.1 +/- 1.0 min) did not differ significantly from those for isof lurane (10.6 +/- 1.3 min). Patients opened their eyes at lower end-tid al minimum alveolar anesthetic concentration (MAC)-fractions of sevofl urane (0.12 +/- 0.01 MAC) than isoflurane (0.15 +/- 0.01 MAC, P < 0.01 ). During recovery, patients who received sevoflurane felt less clumsy (P < 0.001) and less confused (P < 0.005) but had higher pain scores (P < 0.005) than those who received isoflurane. Sevoflurane is more su itable than isoflurane for single-breath induction, because it produce s a smoother induction with a lower incidence of complications and bet ter patient acceptance.