Premixed versus sequential administration of intrathecal fentanyl as a bupivacaine adjuvant in lower limb orthopedic surgeries: a prospective randomized controlled study

Abstract

Introduction: Intrathecal fentanyl is routinely mixed with hyperbaric bupivacaine during spinal block, but this may alter the baricity of both drugs and hence affect their spread and action. Aim: This study aimed to compare the sequential administration of intrathecal fentanyl and bupivacaine to the routine mixing of the two drugs as regard the block characteristics, the postoperative analgesia duration, and the adverse effects. Methods: Current prospective, controlled, randomized trial was carried out on 100 adult participants subjected to lower limb orthopedic surgeries under spinal anesthesia. Subjects were allocated randomly into two equal groups (50 each). Group P: received premixed solution of hyperbaric bupivacaine (HB) 0.5 % (12.5 mg) plus 25 µg of fentanyl in the same syringe and group S: received 25 µg of fentanyl followed by 12.5 mg of HB in sequential manner. Block characteristics, time to the first rescue pethidine request, number of participants who requested for pethidine within the first 6 postoperative hours, and adverse effects were assessed. Results: Group S patients had statistically significantly faster onset of both sensory (4.58 ± 1.5 vs 5. 40 ± 1.8 min, p = 0.02) and motor block (5.79 ± 1.5 min versus 6.64 ± 1.9 min, p = 0.01), shorter time to achieve the highest sensory level (6.12 ± 1.96 min vs 8.77 ± 2.5min, p = 0.00), and a longer time till the first postoperative rescue analgesic need (252.26 ± 39.3 min versus 234.70 ± 40.2 min, p = 0.03). Group P patients achieved statistically significantly higher level of sensory blockade and showed longer sensory block duration (216.30 ±30.8 vs 199.44± 23.8, p = 0.003). Adverse effects were comparable in both groups. Conclusions: The sequential administration of fentanyl and hyperbaric bupivacaine improves the spinal block characters in patients subjected to lower limb orthopedic surgeries with comparable adverse effects profile in comparison to mixing both drugs.