To study the effects of intravenous dexmedetomidine on characteristics of subarachnoid block using hyperbaric bupivacaine in lower limb orthopaedic surgery

Background: We studied the effects of intravenous dexmedetomidine on characteristics of subarachnoid block with respect to sensory block, motor block, duration of postoperative analgesia and complications encountered. Materials and methods: Hundred patients of American Society of Anesthesiologists (ASA) grade I or II (20 – 50 years) presenting for lower limb orthopaedic surgery were included in the study. All patients received 2.5 ml of 0.5% hyperbaric bupivacaine intrathecally followed by: Group D (n=50) - Loading dose of 1 µg kg-1dexmedetomidine over 10 minutes started 20 minutes after spinal block + maintenance dose of 0.4 µg kg-1 hr-1dexmedetomidine till the end of surgery; Group P (n=50) - same calculated volume of normal saline as loading dose over 10 minutes + maintenance till end of surgery. Data regarding the onset and regression of sensory and motor block, VAS score, duration of analgesia, sedation score, haemodynamic parameters and complications were recorded. Results: The time of two segment regression, regression to S2 dermatome and time of VAS ≥ 4 was more in group D than in group P (p< 0.001). Patients in group D had a significantly higher sedation score than group P (p< 0.001). Dexmedetomidine significantly reduced the post-op requirement of diclofenac injection (p< 0.001). No other complications were observed in the two groups. Conclusion: Intravenous dexmedetomidine after spinal block resulted in significant prolongation of time to two segment regression of sensory block, motor block and time to VAS 4; reduced postoperative analgesic requirement and good sedation levels with maintenance of haemodynamic parameters.