Detection of Postpartum Hemorrhage Using Compensatory Reserve Index in Patients Undergoing Cesarean Delivery

Background: Postpartum hemorrhage (PPH) is the leading cause of maternal death worldwide. Early recognition and management are imperative for improved outcomes. The compensatory reserve index (CRI) is a novel physiological parameter that trends changes in intravascular volume, by continuously comparing extracted photoplethysmogram waveforms to a reference model that was derived from a human model of acute blood loss. This study sought to determine whether the CRI pattern was differential between those who do and do not experience PPH during cesarean delivery and compare these results to the American Society of Anesthesiologists (ASA) standards for noninvasive monitoring.

Methods: Parturients undergoing cesarean delivery were enrolled between February 2020 and May 2021. A noninvasive CRI monitor was applied to collect continuous CRI values throughout the intraoperative and immediate postpartum periods. Patients were stratified based on blood loss into PPH versus non-PPH groups. PPH was defined as a quantitative blood loss >1000 mL. Function-on-scalar (FoS) regression was used to compare trends in CRI between groups (PPH versus non-PPH) during the 10 to 60-minute window after delivery. Two subanalyses excluding patients who received general anesthesia and preeclamptics were performed.

Results: Fifty-one patients were enrolled in the study. Thirteen (25.5%) patients experienced PPH. Pregnant patients who experienced PPH had, on average, lower postdelivery CRI values (-0.13; 95% CI, -0.13 to -0.12; P < .001) than those who did not experience PPH. This persisted even when adjusting for preeclampsia and administration of uterotonics. The average mean arterial pressure (MAP) measurements were not statistically significant (-1.67; 95% CI, -3.57 to 0.22; P = .09). Similar trends were seen when excluding patients who underwent general anesthesia. When excluding preeclamptics, CRI values remained lower in those who hemorrhaged (-0.18; 95% CI, -0.19 to -0.17; P < .001).

Conclusions: CRI detects changes in central volume status not distinguished by MAP. It has the potential to serve as a continuous, informative metric, notifying providers of acute changes in central volume status due to PPH during cesarean delivery.