A prospective, randomised, controlled clinical trial to evaluate the effect of nitrous oxide on propofol requirement in elective craniotomy in which entropy was used to measure depth of anaesthesia

Background: Propofol is known to have a favourable effect on cerebral haemodynamics. The role of nitrous oxide (N2O) in neurosurgical anaesthesia is still being debated. The primary aim of this study was to assess the dose-sparing effect of N2O on propofol infusion maintenance dosing. Method: Fifty American Society of Anesthesiology (ASA) grade I and II adults scheduled for elective craniotomies for supratentorial tumours were enrolled in the study. The patients received a standard anaesthetic comprising a fentanyl 2 μg/kg bolus prior to propofol induction. Anaesthesia was maintained with an infusion of fentanyl (2 μg/kg/hour), atracurium and propofol. The patients were randomised into two groups. Group A received 67% N2O. Group B did not receive N2O concomitantly with the propofol infusion. Entropy was used to guide the titration of the propofol infusion in both groups. Results: The propofol maintenance dose requirements were 47% lower in Group A (54.30 ± 11.47 μg/kg/minute) vs. Group B (102.30 ± 14.00 μg/kg/minute), (p < 0.001). Conclusion: The use of supplemental N2O significantly decreased propofol infusion rate requirements, compared with the propofol infusion alone, in ASA I and II patients undergoing elective supratentorial tumour excision.