Evaluation and comparison of intravenous clonidine and intravenous dexmedetomidine on duration of bupivacaine spinal anesthesia

Alpha-2 agonists improve the block characteristics in regional anesthesia, when added to local anesthetics.

To evaluate and compare efficacy of dexmedetomidine and clonidine, as an intravenous adjuvant to intrathecal bupivacaine.

Prospective, randomized, double-blind placebo-controlled study.

75 patients of American Society of Anaesthesiologists status I or II, scheduled for orthopaedic lower limb surgery under spinal anaesthesia, were randomly allocated into three groups of 25 each. Patients in group D received dexmedetomidine 1μg/kg; group C received clonidine 2μg/kg and group PL received physiological saline, each premixed to 20 ml intravenously over 20 min, starting 20 min after the subarachnoid block with 15 mg of 0.5% hyperbaric bupivacaine. Duration of sensory and motor blockade, postoperative analgesia, sedation scores and side effects were recorded.

Parametric testing done using one-way analysis of variance (ANOVA), intergroup comparison with post-hoc analysis Tukey's test. Categorical data analyzed using Chi-square test. P< 0.05 was statistically significant.

Duration of sensory block was significantly prolonged by dexmedetomidine (231.20±24.84 min) and clonidine (200±23.67 min) than placebo (171±12.25 min) (p<0.001). Duration of motor block was 135.20±12.87 min with placebo, 180.40±24.70 min with clonidine and 205.20±25.56 min with dexmedetomidine (p<0.001). Postoperative analgesia was significantly prolonged by dexmedetomidine (255±23.14 min) than by clonidine (221.40+ 24.30 min) and placebo (202.60±14.08 min) (p<0.001). The mean sedation score was significantly higher in dexmedetomidine group.

Single-dose intravenous dexmedetomidine and clonidine given after spinal anaesthesia prolong duration of sensory and motor block and postoperative analgesia.