Effects of intravenous dexmedetomidine or clonidine in patients undergoing knee replacement surgery under spinal anaesthesia: A prospective randomised placebo-controlled study

Objectives:To observe the post-operative pain intensity, recovery time of sensory and motor blockade, time to seek first request for post-operative analgesia including the amount of rescue analgesia and the haemodynamic parameters, respiratory parameters, sedation scoring and adverse effects. Methods:Totally, 150 patients undergoing knee replacement surgery under spinal anaesthesia were randomised into three groups. Group 1 received intravenous dexmedetomidine infusion 0.5 ug kg⁻¹ h⁻¹ till end of the procedure, Group 2 received intravenous clonidine infusion 1 ug kg⁻¹ h⁻¹ till end of the procedure and Group 3 received intravenous normal saline infusion till end of the procedure. All the parameters were observed till the 24 hours post-operatively. Statistical analysis was performed by the SPSS program and p < 0.05 was considered as significant. Result:Post-operative VAS score was significantly higher in Group 3 as compared to Groups 1 and 2 with total rescue analgesia requirement being significantly lower in Group 1 (3.48 ± 5.64 mg) and Group 2 (5.52 ± 9.27 mg) as compared to Group 3 (9.76 ± 11.47 mg). Time to first rescue analgesia was longer in Group 2. The duration of sensory block was significantly higher in dexmedetomidine group (151.30 ± 14.28 min). The duration of motor blockade was significantly higher in dexmedetomidine group (201.20 ± 19.21 versus 192.10 ± 15.78 versus 186.60 ± 15.60 min). Sedation was significantly higher in Group 1 (14 patients) and Group 2 (12 patients). Conclusion:Intraoperative intravenous dexmedetomidine and clonidine provide better post-operative analgesia. Intravenous dexmedetomidine prolongs the duration of sensory and motor blockade after spinal anaesthesia.