BACKGROUND: Unilateral spinal anesthesia prolongs sensory blockade and provides hemodynamic stability. Intrathecal opioids enhance spinal anesthesia without prolonging motor recovery or hemodynamic side effects. The author evaluated the effect of intrathecal fentanyl on unilateral spinal blockade with hyperbaric bupivacaine for knee arthroscopy.

METHODS: Thirty-six healthy patients undergoing unilateral knee arthroscopy randomly received unilateral spinal anesthesia with 0.5% hyperbaric bupivacaine 4 mg (Group I) or 0.5% hyperbaric bupivacaine 4 mg combined with fentanyl 10 µg (Group II). A lateral decubitus position was maintained for 15 minutes after intrathecal injection. The level and duration of sensory and motor blockade were recorded.

RESULTS: The regression time of sensory block by two segments on dependent site was prolonged on Group II more than Group I (P < 0.05). There was no significant difference between two groups in recovery time of sensory and motor block. Unilateral sensory block was observed in 18 patients in Group I (100%) and in 2 patients in Group II (11%). Hemodynamic side effects were minimal in both groups, but pruritus was observed in 6 patients in Group II (33%).

CONCLUSIONS: Small dose of intrathecal fentanyl with bupivacaine unilateral spinal anesthesia prolonged the duration of sensory block on operated site, but did not increase side effects and the duration of motor block and recovery. But intrathecal fentanyl with bupivacaine made disturbance of successful unilateral spinal block by the sensory block of nonoperated site.