A Comparative Study on The Efficacy of Low Dose 0.5% Bupivacaine and Fentanyl Versus Conventional Dose of Hyperbaric Bupivacaine Alone For Lower Segment Caesarean Section

Abstract

Background

Spinal anaesthesia is the preferred anaesthetic technique for Lower Segment Cesarean Section (LSCS). Conventional doses of hyperbaric bupivacaine provide effective surgical blocks but are frequently associated with a high incidence of maternal hypotension. This study evaluated whether a low-dose hyperbaric bupivacaine regimen combined with intrathecal fentanyl improves maternal hemodynamic stability while maintaining high-quality operative block characteristics and neonatal safety.

Methods

This prospective, randomized, double-blind clinical trial evaluated 60 American Society of Anesthesiologists (ASA) physical status II parturients undergoing elective LSCS. Participants were randomly allocated into two equal groups (n=30 each):

• Group B (Conventional-dose): Received 0.5% hyperbaric bupivacaine 1.8 mL (9.0 mg).
• Group BF (Low-dose adjuvant): Received 0.5% hyperbaric bupivacaine 1.6 mL (8.0 mg) combined with fentanyl 0.2 mL (10 mcg) intrathecally.

The primary outcomes included sensory and motor block characteristics and postoperative analgesia duration. Secondary outcomes evaluated intraoperative hemodynamic stability, maternal adverse event profiles, and neonatal Apgar scores.

Results

Parturients in Group BF achieved significantly faster sensory onset times to both the T10 and T6 dermatomes compared to Group B (p = 0.002 and p = 0.033, respectively). The overall duration of effective sensory blockade (96.00 ±10.59 min vs. 82.53 ±15.40 min; p < 0.001) and total postoperative analgesia duration (239.27 ±40.69 min vs. 171.07 ±30.58 min; p < 0.001) were significantly prolonged in the low-dose fentanyl group.

Hemodynamically, Group BF exhibited superior stability, demonstrating a significantly lower incidence of maternal hypotension (20.0% vs. 46.7%; p = 0.028) and a reduced requirement for therapeutic vasopressor support (16.7% vs. 40.0%; p = 0.045) with lower total ephedrine consumption (0.82 ±2.21 mg vs. 5.36 ±8.07 mg; p = 0.004). Pruritus occurred exclusively in Group BF (20.0% vs. 0.0%; p = 0.024). Neonatal Apgar scores at 1 and 5 minutes were statistically comparable between the groups (p > 0.05).

Conclusion

A low-dose intrathecal bupivacaine regimen (8.0 mg) co-administered with 10 mcg of fentanyl provides reliable, rapid surgical anesthesia for Cesarean section while significantly mitigating maternal hypotension and vasopressor requirements, with the added benefit of extended early postoperative analgesia.