Is dexmedetomidine a better sedative agent than clonidine in spinal anesthesia?

Background and Aims: Regional anesthesia offers benefits to patients and anesthetists by keeping the patients awake, preserving the airway reflexes, by providing cardiovascular stability during the procedure and fast postoperative recovery. Patients are often uncomfortable, because of pain at puncture site, recall of procedure and limited duration of blockade. Alpha-2 adrenoreceptor agonists were introduced in anesthesia for their sedative and analgesic effects. The aim of this study was to compare the effects of intravenous dexmedetomidine or clonidine as adjuvants during bupivacaine spinal anesthesia. Methodology: A prospective, randomized study was conducted involving 120 patients scheduled for elective infraumbilical surgery under spinal anesthesia. Patients were randomly divided into three groups (n = 40) and were given the following drugs intravenously as per group allocation: Group A received 1 mu g/kg of dexmedetomidine, followed by an infusion at the rate of 0.5 mu g/kg/h; Group B received 1 mu g/kg of clonidine, followed by an infusion at rate of 1 mu g/kg/h and Group C received normal saline bolus and infusion. Loading dose was given over 10 min, prior to (SAB), followed by a maintenance infusion. Ramsay sedation score of 3-4 was considered as target sedation. Patients were assessed for time required to achieve target sedation, prolongation of analgesia and motor blockade. The hemodynamic parameters and side effects were also observed. Results: The target sedation was achieved significantly earlier in Group A (14.32 +/- 5.25 min) as compared to Group B (30.01 +/- 2.33 min) (P = 0.001). In Group A, the mean duration of analgesia was 208.25 +/- 28.29 min as compared to 169.75 +/- 20.15 min in Group B and 135.25 +/- 22.60 min in Group C (P < 0.05). Duration of motor blockade was increased in Group A (217 +/- 24.697 min) as compared to Group B and C. Conclusion: Intravenous dexmedetomidine infusion is better than intravenous clonidine as it provides earlier onset of adequate sedation along with prolongation of analgesia and motor blockade during bupivacaine spinal anesthesia.