Efficacy and Appropriate Dosage of Isobaric Ropivacaine for Spinal Anesthesia in Patients Undergoing Elective Lower Limb Orthopaedic Surgeries

Background: The dose response of ropivacaine has not been extensively determined yet. This study was conducted to estimate minimum effective local anaesthetic dose and to assess the duration of sensory and motor block, and side effects if any, of intrathecal administration of ropivacaine for lower limb surgeries. Materials and Methods: 120 patients aged between 20 years and 60 years of either sex belonging to ASA Class I and Class II posted for elective lower limb orthopaedic surgeries were randomly selected for the study. The study population was randomly divided by a set of random numbers into 3 groups (Group I= 10mg of isobaric Ropivacaine, Group II= 15mg of isobaric Ropivacaine, Group III= 20mg of isobaric Ropivacaine Statistical comparisons were performed using analysis of variance with post hoc analysis Results: All three groups were comparable regarding the age and gender of the patients and the variation in age and gender distribution between groups was statistically insignificant. Onset of sensory block was statistically significant in three groups. Overall 58 patients (48.3%) successfully completed their surgery. According to our definition the spinal anaesthesia was effective in 10 (25%), 20 (50%), 36 (90%) in 10mg, 15mg and 20mg groups respectively. Based on this result we determined ED 50 (50% CI) to be 15mg (13-16) and ED 95 (95% CI) to be 20mg (18.5-22.5). Conclusion: We conclude that ropivacaine is a suitable agent for spinal anaesthesia in lower limb orthopaedic surgeries and adequacy of spinal anaesthesia is related to the dose and degree of motor block. Abstract Word Count : 251Word Count : 251