Dose sparing of induction dose of propofol by fentanyl and butorphanol: A comparison based on entropy analysis

BACKGROUND The induction dose of propofol is reduced with concomitant use of opioids as a result of a possible synergistic action. AIM AND OBJECTIVES The present study compared the effect of fentanyl and two doses of butorphanol pre-treatment on the induction dose of propofol, with specific emphasis on entropy. METHODS Three groups of 40 patients each, of the American Society of Anaesthesiologistsphysical status I and II, were randomized to receive fentanyl 2 μg/kg (Group F), butorphanol 20 μg/kg (Group B 20) or 40 μg/kg (Group B 40) as pre-treatment. Five minutes later, the degree of sedation was assessed by the observer's assessment of alertness scale (OAA/S). Induction of anesthesia was done with propofol (30 mg/10 s) till the loss of response to verbal commands. Thereafter, rocuronium 1 mg/kg was administered and endotracheal intubation was performed 2 min later. OAA/S, propofol induction dose, heart rate, blood pressure, oxygen saturation and entropy (response and state) were compared in the three groups. STATISTICAL ANALYSIS Data was analyzed using ANOVA test with posthoc significance, Kruskal-Wallis test, Chi-square test and Fischer exact test. A P<0.05 was considered as significant. RESULTS The induction dose of propofol (mg/kg) was observed to be 1.1±0.50 in Group F, 1.05±0.35 in Group B 20 and 1.18±0.41 in Group B40. Induction with propofol occurred at higher entropy values on pre-treatment with both fentanyl as well as butorphanol. Hemodynamic variables were comparable in all the three groups. CONCLUSION Butorphanol 20 μg/kg and 40 μg/kg reduce the induction requirement of propofol, comparable to that of fentanyl 2 μg/kg, and confer hemodynamic stability at induction and intubation.