Role of prophylactic intravenous calcium in prevention of post-spinal hypotension among women with preeclampsia undergoing caesarean delivery: a placebo controlled randomized clinical trial: Randomized clinical trial of calcium vs placebo for prevention of post-spinal hypotension.

Background: Preeclamptic women, in addition to traditional anti-hypertensive medications, often receive magnesium supplementation and are at increased risk of post-spinal hypotension Post-spinal hypotension increases the risk of fetomaternal morbidity. Calcium is a physiological antagonist of magnesium in vascular smooth muscle. Therefore, the study hypothesized that calcium is better suited for preserving systemic vascular resistance and preventing post-spinal hypotension during cesarean delivery.

Objectives: The study aimed to evaluate the effect of prophylactic calcium administration on post-spinal hypotension in preeclamptic women receiving magnesium supplementation.

Methods: This prospective, randomized, placebo-controlled, double-blinded, two-arm parallel trial was conducted in preeclamptic women receiving magnesium sulfate supplementation undergoing cesarean delivery. The women were randomized to receive intravenous calcium or a placebo (normal saline) before spinal anesthesia. The study drug (calcium gluconate 500 mg or normal saline) was administered over 15 minutes and ended immediately before spinal anesthesia. The primary outcome measure was the incidence of post-spinal hypotension, and secondary outcome measures were postpartum blood loss and maternal and neonatal outcomes.

Results: 100 women (50 each calcium and placebo arm) completed the study. The baseline demographic variables, mean blood pressure and heart rate were comparable. The incidence of post-spinal hypotension was significantly lower in the calcium arm compared to the placebo arm {(32% vs 60%; Relative risk (95% CI); 1.87 (1.18-2.97); p=0.007)}. The mean phenylephrine requirement (5.60±14.59 vs 14.80 ±22.42 mcg; p=0.01) and mephentermine requirement (3.30 ±5.11 mg vs 5.82 ±4.97 mg; p=0.008) was significantly lower in the calcium group. Furthermore, the calcium group's mean postpartum blood loss was significantly lower (406.90 ±94.34 vs 472.20±122.49 ml, p= 0.004). However, the Neonatal Intensive Care Unit admission rate, Apgar score, umbilical artery PH, and maternal serum calcium were comparable.

Conclusion: Prophylactic calcium infusion significantly reduces the incidence of post-spinal hypotension during cesarean delivery in preeclamptic women receiving magnesium supplementation. Furthermore, the effect of prophylactic calcium in decreasing postpartum blood loss is encouraging. However, large trials are required to validate the findings of this study.