Effect of intramuscular and intravenous lidocaine on propofol induction dose.

OBJECTIVE Our purpose was to study whether or not intravenous (IV) administration of lidocaine reduces propofol dose requirement as intramuscular (IM) lidocaine in a placebo-controlled manner. SUBJECTS AND METHODS Seventy-five adult patients with American Society of Anesthesiologists physical status I and II, aged 20-60 years who were scheduled for surgery under general anaesthesia were included in the study. The patients were randomly allocated to 3 groups: IM: intramuscular administration; IV: intravenous administration and C: control. There were 25 patients in each group. The patients in group IM received lidocaine 1.5 mg · kg(-1) administered into the deltoid muscle 10 min before anaesthesia induction. In group IV, the patients received IV lidocaine 1.5 mg · kg(-1), 2 min before anaesthesia induction. Group C patients served as control group who received only propofol injection. Hypnosis after propofol administration was measured with response to verbal commands. RESULTS There were no statistical differences between group IM (100.8 ± 26.1 mg) and group IV (110.8 ± 30.1 mg) regarding the induction dose of propofol (p > 0.05). In group C, the required propofol dose (151.2 ± 27.4 mg) for anaesthesia induction was significantly higher than in the other groups (p < 0.001). No side effect was observed in any patients. CONCLUSION In this study, both IV and IM lidocaine administration were effective in reducing the hypnotic dose of propofol without any side effects. In addition, IV lidocaine may be more comfortable for awake patients.