Calcium Chloride for Prevention of Uterine Atony During Cesarean

Calcium Chloride in the Prevention of Uterine Atony During Cesarean in Women at Increased Risk of Hemorrhage: a Pilot Randomized Controlled Trial and Pharmacokinetic Study

In this pilot study, investigators will administer calcium chloride or placebo to pregnant women undergoing Cesarean delivery who have been identified as high risk for hemorrhage due to poor uterine muscle contraction, or atony. They will assess whether a single dose of calcium given immediately after the delivery of the fetus decreases the incidence of uterine atony and bleeding for the mother. The pharmacokinetics of calcium chloride in pregnant women will also be established. Data from this pilot study of 40 patients will be used to determine sample size and appropriateness of a larger randomized clinical trial.

Poor contraction of the uterus, also known as uterine atony, is the leading cause of severe blood loss during Cesarean section, both in the US and worldwide. Exogenous calcium has been shown to increase uterine muscle contraction in in vitro and in animal studies. Calcium is also an essential factor in normal blood clotting. Anesthesiologists commonly administer intravenous calcium chloride during Cesarean as well as other types of surgery, but formal randomized studies to determine efficacy in improving uterine tone have not been performed.

In this pilot, randomized controlled study, the anesthesiologist will administer a one-time dose of intravenous calcium chloride 1gram versus placebo at the time of fetal delivery to women identified as having high risk of hemorrhage during Cesarean delivery. Primary outcome assessed will be a composite measure of uterine atony. Data from the pilot study will be used to perform power and sample size calculations for a larger study. Secondary outcomes assessed will include total blood loss, subjective assessment of uterine tone by the blinded obstetrician performing surgery, safety, side effects, and pharmacokinetic profile of calcium chloride in pregnant women.

Inclusion Criteria:

Pregnant female subjects at Lucile Packard Children's hospital / Stanford hospital undergoing Cesarean will be screened for inclusion in the study based upon presence of at least 2 risk factors for uterine atony/ postpartum hemorrhage. The risk factors include the following:

• intrapartum Cesarean delivery
• failed operative vaginal delivery with forceps or vacuum
• magnesium infusion
• chorioamnionitis
• multiple gestation
• polyhydramnios
• preterm delivery <37 weeks
• prior history of postpartum hemorrhage
• labor induction or augmentation with oxytocin
• advanced maternal age
• obesity with body mass index >40

Exclusion Criteria:

• a degree of case urgency to which taking time to consent for the study could compromise patient care, determined by anesthesiologist or obstetrician
• patient age <18 years or >50 years
• renal dysfunction with serum Creatinine > 1.0
• abnormal cardiac function or history of arrhythmia
• patient taking digoxin
• patient currently taking a calcium channel blocker for a cardiovascular indication