Background and objective: The bispectral index of the electroencephalogram is a measure of the hypnotic component of anaesthesia and can be used to guide the administration of anaesthesia. This study compares bispectral index-guided anaesthesia with remifentanil and either propofol or isoflurane.
Methods: Eighty consenting patients were randomly assigned to two groups. Following induction with propofol and remifentanil, anaesthesia was maintained with remifentanil/propofol or remifentanil/isoflurane. Remifentanil infusion rates were guided by haemodynamic responses – maintaining mean arterial pressure and heart rate within 20% of baseline. Propofol and isoflurane administration was guided using the bispectral index (45–60). Thirty minutes before the end of surgery, morphine was administered (0.15 mg kg−1 intravenously). Fifteen minutes before end of surgery, propofol and isoflurane were reduced (bispectral index 60–75). At the end of surgery, the anaesthetic agents were discontinued. Groups were compared for recovery, remifentanil doses and signs of inadequate anaesthesia using the χ2-test and ANOVA (P < 0.05).
Results: The duration of surgery was longer in the propofol/remifentanil group (121 ± 53 versus 94 ± 40 min). Recovery data were not different between groups. The remifentanil infusion rate was significantly lower with additional isoflurane (0.18 ± 0.06 μg kg−1 min−1) than with additional propofol (0.31 ± 0.20 μg kg−1 min−1). The propofol infusion rate was 123 ± 48 μg kg−1 min−1; isoflurane concentration was 0.66 ± 0.13%.
Conclusions: Bispectral index-guided anaesthesia with remifentanil plus propofol or isoflurane results in the absence of postoperative recall and a fast recovery with both drug combinations. In our patients, at comparable bispectral index-levels, haemodynamic control requires higher doses of remifentanil with propofol than with isoflurane.