Effect of premixed and sequential intrathecal fentanyl on spinal block characteristics

The optimal method of intrathecal fentanyl administration with hyperbaric bupivacaine remains uncertain, as premixed and sequential techniques may influence block characteristics differently. In this prospective observational comparative study, 42 ASA I-II adults (21 per group) received fentanyl 0.5 ml with hyperbaric bupivacaine 2.5 ml either premixed or sequentially. Sequential administration produced faster sensory onset at T10 (5.00±1.37 vs 6.48±1.32 min) and motor onset (6.10±1.37 vs 8.00±1.30 min) with longer sensory and motor regression times. Time to first rescue analgesia was also longer (205.33±12.08 vs 175.38±14.41 min), suggesting earlier onset and prolonged block with the sequential technique.