Abstract 4372977: Lactate Levels as a Prognostic Marker in Postpartum Hemorrhage: A Comparison with Shock Index, MEWS, and mREMS in the Emergency Department

Background: Postpartum hemorrhage (PPH) remains one of the leading causes of maternal morbidity and mortality worldwide. Rapid identification of women at risk of poor outcomes is essential in emergency settings to guide appropriate resuscitation and management. Aim: This study aimed to assess the prognostic value of lactate levels measured upon admission to the emergency department (ED) in women with PPH and to compare their predictive performance against other early warning scores, including the shock index, modified early warning score (MEWS), and modified rapid emergency medicine score (mREMS). Methods: We conducted a retrospective analysis of 424 women diagnosed with PPH who presented to a tertiary hospital emergency department in South Korea between January 2013 and December 2023. Clinical and laboratory data at ED admission were analyzed in relation to key outcomes: massive transfusion, hysterectomy, uterine artery embolization, and intensive care unit (ICU) admission. Receiver operating characteristic (ROC) curves and multivariable logistic regression were used to evaluate the predictive capacity of each indicator. Results: Elevated lactate levels were significantly associated with the need for massive transfusion (cut-off: 2.95 mmol/L; AUC = 0.86) and hysterectomy (cut-off: 3.05 mmol/L; AUC = 0.84). A combined model of lactate and shock index improved predictive performance(AUC = 0.88) for massive transfusion compared to lactate alone. In multivariable analysis, lactate (OR = 1.67), prothrombin time/international normalized ratio (OR = 1.86), and total CO2 (OR = 1.32) were independently associated with massive transfusion. Fibrinogen levels independently predicted embolization, while total CO2 and triage acuity (as assessed by Korean Triage and Acuity Scale) were associated with ICU admission. Conclusion: Lactate levels provide valuable prognostic information for identifying high-risk PPH patients in emergency care. When used in combination with the shock index, predictive accuracy is further improved, supporting the clinical use of composite indicators for early risk stratification.