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.