CLINICAL COMPARISON OF SEVOFLURANE AND ISOFLURANE WHEN ADMINISTERED WITH NITROUS-OXIDE FOR SURGICAL-PROCEDURES OF INTERMEDIATE DURATION

The purpose of this study was to compare the haemodynamic effects and emergence times of anaesthesia with sevoflurane with those of isoflura ne when the agents were administered with nitrous oxide to adult inpat ients (ASA I and II) undergoing surgery of at least an hour in duratio n. Fifty patients were randomly assigned to receive either 0.65 minimu m alveolar concentration (MAC) (1.3%) sevoflurane or 0.65 MAC (0.8%) i soflurane together with 60% nitrous oxide following induction with thi opentone, fentanyl, and succinylcholine. Systemic blood pressure and h eart rate trends were similar for both groups for the duration of anae sthesia. However, differences in systolic blood pressure measurements were noted at one minute after incision (99 +/- 3 mmHg, mean +/- SE, i n the sevoflurane group compared with 109 +/- 4 mmHg for isoflurane), and at emergence (125 +/- 3 mmHg for sevoflurane, 134 +/- 3 mmHg for i soflurane), and in diastolic blood pressure measurements at five minut es after intubation (64 +/- 2 mmHg for sevoflurane, 73 +/- 3 mmHg for isoflurane). Recovery of response to command was more rapid after disc ontinuation of sevoflurane-nitrous oxide (9.9 +/- 1.1 min) than after isoflurane-nitrous oxide (13.9 +/- 1.3 min). Despite earlier emergence , patients who had received sevoflurane did not request postoperative analgesia sooner. We conclude that the purported advantages of sevoflu rane, namely haemodynamic stability and rapid emergence, can be expect ed even when the agent is administered at 0.65 MAC (1.3%) in nitrous o xide to a typical adult surgical population undergoing procedures of i ntermediate duration (2.3 +/- 0.2 hr).