Comparison of Different Dosage of Intrathecal Morphine as an Adjuvant to Hyperbaric Ropivacaine in Lower Limb Orthopaedic Surgeries: A Double-blinded Randomised Controlled Study

Abstract

Introduction: Spinal anaesthesia with hyperbaric bupivacaine is the cornerstone of lower limb surgeries. With introduction of commercially prepared hyperbaric ropivacaine, its use has increased considerably as an effective alternate. Aim: To evaluate the analgesic and blockade characteristics of different dosages of morphine when used intrathecally as an adjuvant with hyperbaric ropivacaine in lower limb orthopaedic surgeries. Materials and Methods: The present double-blinded randomised controlled study was conducted on 114 patients undergoing lower limb orthopaedic surgery under spinal blockade, Patients were divided into three groups. Group R received 3 mL of 0.75% hyperbaric ropivacaine, Group RM1 received 3 mL of hyperbaric ropivacaine with 100 µg morphine, and Group RM2 received 3 mL of 0.75% hyperbaric ropivacaine with 200 µg morphine, respectively. The onset and duration of sensorimotor blockade, duration of analgesia, visual analogue scale for pain and incidence of adverse effects were compared in three groups. Analysis of Variance (ANOVA) test was used for quantitative data while Chisquare test was used for qualitative data. Results: Demographic data was comparable in all the groups. Group RM2 has significantly prolonged postoperative analgesia {11.59±0.60 hours (p<0.001)}. Analgesic requirement was lower in groups RM1 (1.58±0.37) and RM2 (1.26±0.45) as compared to Group R (1.58±0.50) (p<0.001). A statistically significant difference was observed between the total duration of sensory blockade in Group R (201.95±7.12 min), Group RM1 (232. 21±7.48 min) and Group RM2 (467±21.04 min) (p<0.001). The duration of motor blockade was also increased in Group RM2 (424±25.78 min). Conclusion: Addition of 200 µg morphine to hyperbaric ropivacaine provides haemodynamically stable anaesthesia with prolonged duration of analgesia and sensory blockade. This dosage does not have any additional adverse effects.