Use of Preoperative Sodium Bicarbonate Among Women With Obstructed Labor

Oral bicarbonate is a safe, cheap and effective acid buffer, widely used in sports to improve performance because of its ability to prevent and reverse the effects of metabolic acidosis. Clinically, it is used in intensive care units to treat patients with overwhelming infections or poisoning. In low resource settings, obstructed labor (OL) is a major problem that accounts for 22% of maternal deaths. The fetal harm of OL comes from intrapartum asphyxia, characterized by accumulation of hydrogen ions that cross the placental barrier to cause fetal acidosis. Acidosis causes failure of basic cellular functions resulting into cell death. In a recent Randomised Clinical Trial, the investigators found that 61% of 477 women with OL were acidotic (lactate >4.8 mmol/L), with a median capillary blood lactate level of 6.9 (3.4-13) mmol/L.

The investigators propose an early phase III, placebo-controlled dose-ranging trial to determine the efficacy and safety of a pre-operative infusion of sodium bicarbonate in women with obstructed labour (OL). In a ratio of 1:1:1: 1 100 mls (8.4g), 150 mls (12.6g) and 200 mls (16.8g) of 8.4% sodium bicarbonate solution, or placebo (50 mls of Normal Saline 0.9%). The primary outcome will be mean change in acidosis (pH and lactate levels) from baseline. The secondary outcomes will be neonatal death, safety of sodium bicarbonate, pharmacokinetics of sodium bicarbonate in pregnant women, primary postpartum haemorrhage, sepsis, and maternal death.

Inclusion criteria

• Patients with obstructed labour
• Must be a singleton pregnancy
• Must be a term pregnancy (≥37 weeks of gestation)
• Must be in cephalic presentation.

Exclusion criteria

• Patients with other obstetric emergencies such as antepartum haemorrhage, preeclampsia and eclampsia (defined as elevated blood pressure of at least 140/90 mm Hg, urine protein of at least 2+, any of the danger signs and fits), premature rupture of membranes and intrauterine fetal death.
• Patients with comorbidities such as diabetes mellitus, sickle cell disease, renal disease, liver disease and heart disease.
• Patients with hypokalaemia (148 mmol/L) and alkalosis (bicarbonate >22 mmol/L) because they are more likely to develop adverse drug reactions