Comparative evaluation of fentanyl and lignocaine for reduction of induction dose of propofol and attenuation of hypertensive response to laryngoscopy and intubation

Background: Propofol is a very popular and potent intravenous hypnotic agent. The major drawbacks of anaesthetic induction with propofol are a greater degree of hypotension and inadequate attenuation of the hypertensive response to intubation. In order to reduce these unwanted side effects, adjuvant agents like opioids or local anaesthetics may be used to decrease the propofol induction dose requirement.
Aims: Aims of our study were to compare the effects of fentanyl and lignocaine on Induction dose of propofol as well as on hypertensive response to laryngoscopy and intubation.
Study design: Randomized double-blind placebo-controlled study
Methods: We had randomized 90 adult patients of ASA grade I and II, aged 18 to 60 years, of either sex, weighing 40 to 80 kg, scheduled for elective surgery under general anaesthesia, into one of the three groups (n=30). Each patient received 2 ml of pretreatment solution over 5 seconds, followed one minute later by propofol injected @2.5 ml every 5 seconds and continued until loss of verbalization. Group I: 2 ml 2% lignocaine (40 mg); Group II (fentanyl): 2 ml fentanyl (100 g); Group III (placebo): 2 ml normal saline. The total dose of propofol to achieve loss of response in each patient was recorded. HR and BP were monitored before laryngoscopy and 1, 2 and 5 minutes after laryngoscopy and every 15 minutes thereafter. All the data were recorded as frequencies and meanSD. All the statistical operations were performed using Statistical Package for Social Sciences (SPSS) Version 13.0. Intergroup differences have been compared using chi-square test, ANOVA, student's "t" test and Mann-Whitney U test. The confidence level of the study has been kept at 95%, hence a "p" value <0.05 has been considered as statistically significant.
Results: The mean induction dose of propofol per unit body weight varied in the three groups significantly (p=0.033). In Group III, the quantity of propofol mixture given was 1.70±0.18 mg/kg followed by 1.67±0.26 mg/kg in Group I and 1.54±0.28 mg/kg in Group II. It was significantly higher in Group I as compared to Group II (p=0.031) and in Group III as comared to Group II(p=0.020) whereas no significant difference was seen between Groups I and III (p=0.938). There was no significant difference in mean HR among three groups at baseline as well as at different time intervals, the increase in HR being least significant in group II. A significant difference in MAP (p<0.05) was seen at 1 minute, 2 minutes, 5 minutes and 30 minutes after laryngoscopy, MAP being least in group II at all these points of time except at 5min.
Conclusions: Our study showed that fentanyl was much more effective in reducing the induction dose of propofol as compared to lignocaine when given 1 min before propofol. Also, fentanyl seemed to be effective in attenuating the HR response to laryngoscopy and intubation and was more effective than lignocaine in attenuating the hypertensive response to laryngoscopy.