Association between ionised calcium and severity of postpartum haemorrhage: a retrospective cohort study

Abstract

BackgroundPostpartum haemorrhage (PPH) is often complicated by impaired coagulation. We aimed to determine whether the level of ionised calcium (Ca2+), an essential coagulation co-factor, at diagnosis of PPH is associated with bleeding severity. MethodsThis was a retrospective cohort study of women diagnosed with PPH during vaginal delivery between January 2009 and April 2020. Ca2+ levels at PPH diagnosis were compared between women who progressed to severe PPH (primary outcome) and those with less severe bleeding. Severe PPH was defined by transfusion of ≥2 blood units, arterial embolisation or emergency surgery, admission to ICU, or death. Associations between other variables (e.g. fibrinogen concentration) and bleeding severity were also assessed. ResultsFor 436 patients included in the analysis, hypocalcaemia was more common among patients with severe PPH (51.5% vs 10.6%, P<0.001). In a multivariable logistic regression model, Ca2+ and fibrinogen were the only parameters independently associated with PPH severity with odds ratios of 1.14 for each 10 mg dl−1 decrease in fibrinogen (95% confidence interval [CI], 1.05–1.24; P=0.002) and 1.97 for each 0.1 mmol L−1 decrease in Ca2+ (95% CI, 1.25–3.1; P=0.003). The performance of Ca2+ or fibrinogen was not significantly different (area under the curve [AUC]=0.79 [95% CI, 0.75–0.83] vs AUC=0.86 [95% CI, 0.82–0.9]; P=0.09). The addition of Ca2+ to fibrinogen improved the model, leading to AUC of 0.9 (95% CI, 0.86–0.93), P=0.03. ConclusionsCa2+ level at the time of diagnosis of PPH was associated with risk of severe bleeding. Ca2+ monitoring may facilitate identification and treatment of high-risk patients.