Efficacy of dexmedetomidine as intrathecal adjuvant in subarachnoid block and postoperative analgesia

Various adjuvants have been used intrathecally to improve the quality and duration of the spinal anaesthesia along with better postoperative analgesia We studied the effect of dexmedetomidine as intrathecal adjuvant to local anaesthetic agent in subarachnoid block. The primary goal was to study the onset and duration of sensory and motor block. The secondary goal was to note the time for first rescue analgesic, total requirement of rescue analgesic, quality of block and any complications.

Sixty patients age 18 to 60 years, ASA I-II, posted for lower limb orthopaedic surgeries were randomly allocated into two equal groups based on computer generated randomization: Group B: Inj. Bupivacaine 0.5% hyperbaric 3ml(15mg) + 0.15cc normal saline. Group D: Inj. Bupivacaine 0.5% hyperbaric 3ml(15mg) + Inj. Dexmedetomidine 15μg(0.15ml). All the patients were observed for onset of sensory and motor block, two segment regression time, total sensory and motor block duration, time to first rescue analgesic, total number of doses of rescue analgesia in 24 hours postoperatively and side effects if any.

The demographic variables were comparable in the two groups. The onset of sensory block was faster in group B (p=0.002) with no significant difference in the onset of motor block in two groups. The duration of sensory and motor block in Group D was significantly prolonged (p<0.0001). The quality of block was better in Group D.

Dexmedetomidine as an adjuvant to local anaesthetic agents in subrachnoid block delays onset of sensory block with no effect on the onset of motor blockade. The duration of sensory and motor blockade is significantly longer. The time for first rescue analgesic is prolonged with decreased requirement of rescue analgesics postoperatively. Apart from improving the quality and duration of the subarachnoid block, additional properties of dexmedetomidine like sedation and as antishivering agent are additional benefits when used as intrathecal adjuvant.