Comparison of intrathecal dexmedetomidine and fentanyl on quality of subarachnoid block in patients undergoing lower abdominal surgeries: a randomized double blinded study

Local anaesthetics have relatively short duration of action. Various adjuvants have been used to increase duration of block under subarachnoid block. The duration of surgical intervention varies from patient to patient and are associated with visceral manipulation causing somatic and visceral pain. Hence an attempt is made in this study to increase duration of block and also to cover postoperative analgesia by adding adjuvants to intrathecal bupivacaine. Alpha-2 adrenoceptor agonists act on dorsal horn of spinal cord and in combination with local anaesthetics increase the duration of sensory and motor block following subarachnoid block and also intrathecal opioids are known to prolong duration of subarachnoid block. The present study was done to compare the effects of intrathecal dexmedetomidine and fentanyl on duration of sensory and motor block and time for first post-operative analgesia.

Sixty patients of ASA I, II scheduled for lower abdominal surgeries under subarachnoid block were allocated to receive either 10mg bupivacaine plus 5mcg dexmedetomidine [Group D, n=30] or 10mg bupivacaine plus 25mcg fentanyl [Group F, n=30] by double blinded study after giving informed written consent. Level of block achieved, duration of sensory and motor block and time for first post operative analgesic was noted. Any >20% fall in BP was treated with ephedrine and heart rate <60bpm was treated with atropine.

The study showed that Group D patients had prolonged duration of motor block for upto six hours and required analgesic after nine hours following subarachnoid block where as in Group F patients duration of motor block was three hours and required analgesic at three and half hour with statistical significance [p<0.05].

Dexmedetomidine when used intrathecally is a better alternative than intrathecal fentanyl for prolonging the duration of sensory and motor block as well as prolonging time for first post operative analgesic.