Maternal Body Weight and Estimated Circulating Blood Volume: A Review and Practical Nonlinear Approach

Abstract

(Br J Anaesth 2022;129:716e725) Postpartum hemorrhage is a leading cause of maternal morbidity and mortality. The volume of blood loss is an important measure in assessing the severity of hemorrhage and determining appropriate treatment. Maternal circulating blood volume (CBV) also requires accurate estimation to determine necessary interventions and management strategies. CBV does not increase at a proportional rate to body composition, yet linear calculations are utilized to estimate maternal CBV. While the current linear model can adequately estimate CBV for many patients, it can lead to miscalculations for patients with higher or lower body mass. The overestimation of CBV can result in inappropriate thresholds for intervention. This review describes physiological changes during pregnancy relevant to blood volume and proposes a tool for a more accurate estimation of CBV.