Comparison of efficacy of intravenous dexmedetomidine with intravenous ketamine in allaying procedural discomfort during establishment of subarachnoid block

Background: Procedural discomfort is experienced by patients during the establishment of subarachnoid block even after good preoperative counseling and adequate premedication. The fear of needle prick, back pain during and after subarachnoid injection are becoming the leading causes for patient refusal to spinal anaesthesia. To enhance comfort and to overcome the denial, procedural sedation that would provide good analgesia, faster recovery and amnesia is inevitable.

Materials and methods:  Patients with ASA status I and II posted for elective surgeries under subarachnoid block were premedicated with midazolam 0.05mg/kg and pre-loaded with 10 ml/kg ringer lactate solution. They were randomized into 2 groups of 30 each. Group D received dexmedetomidine 1mcg/kg bolus over 10 min, group K received ketamine 0.3mg/kg intravenously.  University of Michigan sedation score, ease of positioning, prick response, verbal response, hallucinations, recall of procedure and patient satisfaction were evaluated.

Results: Both the drugs produced adequate sedation for performing subarachnoid block, UMSS score response to needle prick was comparable between them. Significant difference was observed during positioning the patient for subarachnoid block. Patients sedated with dexmedetomidine were able to position themselves without any help whereas patients sedated with ketamine required one or two persons help. In maintaining verbal response during the procedure both the drugs showed significant difference between them. In group D, most of the patients maintained the verbal response from immediately after bolus to throughout the study. Whereas in group K, no patient responded  to verbal command after bolus up till 3min and majority of them (40%) regained verbal response only at 4min after bolus injection. There were no hallucinations and no recall of events in both groups. Except one patient in group D, all the patients were satisfied and willing to undergo subarachnoid block if need arises.

Conclusion: We conclude that both ketamine and dexmedetomidine provided adequate sedoanalgesia for performing subarachnoid block. Dexmedetomidine was advantageous in terms of maintaining verbal response and ability to positioning themselves.