A comparative evaluation of the analgesic efficacy of low doses of intrathecal neostigmine and bupivacaine with plain bupivacaine in lower limb surgery

Abstract

Intrathecal neostigmine prolongs the duration of analgesia and also appropriate dose reduces the associated side effects. The present study was conducted to evaluate the analgesic efficacy, identify the optimum dose using 3 different doses of neostigmine in combination with bupivacaine in comparison with bupivacaine alone for the intra & postoperative period. Eighty patients of ASA I & II undergoing lower limb surgery under spinal anaesthesia were enrolled and divided into 4 groups of 20 each. Group I: bupivacaine control group, Group II: Bupivacaine + 12.5 µgm Neostigmine, Group III: Bupivacaine +25 µgm Neostigmine, Group IV: Bupivacaine + 50µgm Neostigmine. Hemodynamic parameters, sensory and motor characteristics and adverse effects if any were noted. Pain was assessed using visual analog scale (VAS) in postoperative period hourly for 12 hours & then at 24hours. Onset, duration and level of sensory block were recorded along with onset and duration of motor block. Largest dose (50mgm) produced an increase in duration of analgesia by 16.60min (an increase of 20.10%) compared to control group. The 25mgm intrathecal neostigmine resulted in an increase of 7.20min (an increase by 8.25%). The dose of 50mgm neostigmine in comparison with 25mgm dose significantly prolonged the duration of two segment regression, effective and complete analgesia, with no increase in the incidence of nausea and vomiting and hence 50mgm appears to be the optimum dose amongst the doses considered in our study for intrathecal administration in lower limb surgery.