A randomised prospective study on the effect of intramuscular lignocaine and bupivacaine on induction dose of thiopentone sodium

Introduction: The combination of regional and general anaesthesia is popular and there is growing interest in the possible interactions of the local anaesthetic agents(LA) with drugs used for general anaesthesia. The purpose of this study is to evaluate the hypnotic interaction between Thiopentone sodium with Lignocaine and Bupivacaine. Materials and Method: 90 ASA grade I and II patients of either sexes between the age groups of 18 to 50 years, scheduled to undergo various elective surgical procedures under general anaesthesia were included in the study. The patients were randomly allocated into three groups of 30 patients each. Group C received 3 ml of normal saline intramuscularly (i.m.) 10 minutes before induction, group L received lignocaine (2%) 2mg/kg body weight i.m 10 minutes before induction and group B received bupivacaine (0.5%) 1 mg/kg body weight i.m. 30 minutes before induction. General anesthesia was then induced with Thiopentone sodium till loss of eyelash reflex and the dose required was noted. The heart rate and blood pressure were noted for five minutes post induction. Results: The induction dose of thiopentone sodium in the group C was 4.64±0.35 mg/kg body weight (BW) it was significantly higher than the group L 3.65±0.30 mg/kg BW(p<0.001) and group B 3.23±0.22 mg/kg BW(p<0.001) The induction dose was reduced by 21% and 30% in the lignocaine and bupivacaine group respectively. Group L and B had a significantly attenuated response to intubation. Conclusion: Intramuscular lignocaine and bupivacaine significantly reduce the induction dose of thiopentone sodium.