Comparative Study of Premixed Versus Sequential Administration of Hyperbaric Bupivacaine and Fentanyl for Subarachnoid Block in Caesarean Section: A Randomized Controlled Trial.

BACKGROUND: Spinal anaesthesia is the standard technique for elective caesarean section due to its simplicity, rapid onset, and maternal safety profile. While combining hyperbaric bupivacaine with intrathecal fentanyl enhances anaesthetic efficacy, the sequential drug administration may influence the spread, block dynamics, and haemodynamic stability. METHODS: In this prospective, randomised controlled study, 180 ASA I-II parturients were allocated to either Group M (premixed bupivacaine 9 mg + fentanyl 15 mcg) or Group S (sequential administration of the same drugs). Primary outcomes were time to achieve T5 sensory level, duration of sensory and motor blocks, and incidence of hypotension. Secondary outcomes included vasopressor use, Apgar scores, and umbilical cord blood gas analysis. RESULTS: Group S achieved T5 sensory level significantly faster than Group M (2.88 ± 2.22 vs. 6.04 ± 2.59 min; P = 0.0001). The duration of sensory block was longer in Group S (151.59 ± 22.46 min vs. 123.49 ± 22.64 min; P = 0.0001). Incidence of hypotension was lower in Group S (1.1%) compared to Group M (2.2%) (P = 0.563). Phenylephrine use was also reduced in Group S (P = 0.563). Apgar scores and umbilical cord blood gases were comparable between groups (P > 0.05). CONCLUSION: Sequential intrathecal administration of hyperbaric bupivacaine and fentanyl provides superior sensory block dynamics and improved haemodynamic stability compared to premixed administration, without compromising neonatal outcomes. This technique is simple, effective, and suitable for routine obstetric anaesthesia.