Background: Restoration of brain temperature during CPB rewarming may cause patient to sweat, and may result in inadequate depth of anaesthesia. The aim of this study was to investigate the possible correlation between sweating and awareness, and the effect of midazolam on both.

Methods: Forty four nonpremedicated patients undergoing conventional cardiac surgery were allocated to the study. Anaesthetic induction was performed with fentanyl (30 g/kg, IV) (Group 1; n = 22), or fentanyl (20 g/kg; IV) and midazolam (0.1 mg/kg, IV) (Group 2; n = 22). Anaesthesia was maintained with fentanyl (0.1 _g kg-1 min-1, IV) and isoflurane (0.8%) within 100% oxygen in both groups. In the second group additional dose of midazolam (0.1 mg kg-1, IV) was given just before starting to rewarm the patient. Rectal temperature was monitored continuously and noted at lowest point, at highest point and every five minutes. Sweating was noted, starting with rewarming until the end of the rewarming period, scored from 0 to 3 (0 = no sweat, 1 = a little sweat on the forehead, 2 = sweat on forehead and in the face, 3 = widespread sweat in face, neck, and head). On the postoperative first day patients were tested for awareness. Groups were compared for both awareness and sweating, and any possible correlation between sweating and awareness was investigated.

Results: Awareness was observed in 12 patients in Group 1, and two patients in Group 2, and this difference between groups was statistically significant. The rate of sweating was lower in Group 1 than Group 2 (63.55% and 81.82%, respectively), although the degree of sweating was higher in Group 2 (2.28 vs. 2, respectively). These differences were not statistically significant. There was no correlation between sweating and awareness.

Conclusions: Our data suggest that addition of midazolam to fentanyl anaesthesia attenuates the awareness but not the rate and the degree of sweating.

Keywords : Rewarming, sweating, awareness, midazolam, fentanyl