Comparative Study of Fixed Dose versus Height-adjusted Dose of Heavy Bupivacaine in Spinal Anesthesia for Elective...

Maternal hypotension is the most common and significant complication of spinal anesthesia for cesarean delivery, increasing maternal nausea, vomiting, and risk of fetal acidosis. The traditional fixed intrathecal dose of 0.5% hyperbaric bupivacaine does not account for patient height, an important determinant of block spread and sympathetic blockade.

In this single-center, prospective, double-blind, randomized controlled trial, 60 American Society of Anesthesiologists I-II parturients undergoing elective lower-segment cesarean section received either a fixed intrathecal dose of 0.5% hyperbaric bupivacaine 2.2 ml (Group F) or a height-adjusted dose of 0.06 mg cm-1 body height (Group H; ≈1.7-2.1 ml). No intrathecal opioids or adjuvants were given. Standard preloading, monitoring, and management of hypotension and bradycardia were applied. The primary endpoint was maternal hypotension; secondary endpoints were block characteristics, vasopressor requirement, maternal side effects, and neonatal Apgar scores.

Baseline demographics and hemodynamics were comparable. Hypotension occurred in 63% of Group F versus 27% of Group H (P < 0.01). Group H experienced significantly smaller reductions in systolic and mean arterial pressure. Patients in this group also required fewer mephentermine boluses (0.8 ± 0.6 vs. 2.3 ± 1.1) and a lower total vasopressor dose (3.4 ± 2.1 mg vs. 9.2 ± 3.5 mg), with all differences being statistically significant (P < 0.001). Anesthetic quality and motor block were equivalent. Nausea and vomiting were reduced (7% vs. 23%, P = 0.03). Neonatal Apgar scores exceeded 8 in both the groups, with no neonatal intensive care unit admissions.

Height-adjusted intrathecal bupivacaine ensures reliable surgical anesthesia with improved maternal hemodynamic stability and fewer side effects, without compromising neonatal outcomes.