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

ABSTRACT

The induction dose of propofol is reduced with concomitant use of opioids as a result of a possible synergistic action. 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. Three groups of 40 patients each, of the American Society of Anaesthesiologistsphysical status I and II, were randomized to receive fentanyl 2 microg/kg [Group F], butorphanol 20 microg/kg [Group B 20] or 40 microg/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. 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. 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 B 40. 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. Butorphanol 20 microg/kg and 40 microg/kg reduce the induction requirement of propofol, comparable to that of fentanyl 2 microg/kg, and confer hemodynamic stability at induction and intubation