Background and objective: The role of sevoflurane has not been studied in relation to awareness during anaesthesia. We observed the effect of sevoflurane on the incidence of awareness during cardiopulmonary bypass for open-heart surgery.

Methods: Fifty-nine patients of age >17 yr undergoing open-heart surgery with cardiopulmonary bypass were randomly assigned to two groups. In both groups, induction was with etomidate, dehydrobenzperidol and fentanyl; anaesthesia was maintained with sevoflurane, fentanyl and N2O; vecuronium was used for muscular paralysis. Group 1 (30 patients) received dehydrobenzperidol and fentanyl during cardiopulmonary bypass; Group 2 (29 patients) received sevoflurane and fentanyl. Patients were given different auditory inputs during different phases of surgery. All patients were interviewed with standard questions 8 and 24h postoperatively for evidence of explicit awareness.

Results: Five patients in the dehydrobenzperidol group gave a history of awareness (16.67%) as opposed to none in the sevoflurane group. The difference in the incidences of awareness was significant (P < 0.05), but no differences were found between the interviews conducted at 8 and 24h. Sevoflurane and opioid combination reduced the incidence of awareness in open-heart surgery.