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Peripartum: Central volume status changes during delivery utilizing the Compensatory Reserve Index
Abstract Number: S4A-3
Abstract Type: Original Research
Introduction: Expected blood loss for vaginal delivery is up to 500 ml and 1000 ml for cesarean delivery, but severe hemorrhage is always a risk . Following delivery, auto-transfusion of blood from the uteroplacental circuit results in an increase in cardiac preload and an acute rise in both cardiac output and stroke volume [1,2]. The Compensatory Reserve Index (CRI) is a new adjunctive cardiovascular status indicator that trends changes in intravascular volume relative to the individual patient’s response to hypovolemia . We hypothesized that CRI would accurately detect acute changes in central volume from blood loss and auto-transfusion that occur with both vaginal and cesarean delivery.
Methods: Parturients undergoing a vaginal or operative delivery were enrolled and an investigational, noninvasive CipherOx CRI™ M1 monitor (Flashback Technologies, Louisville, CO) was applied to record CRI values. Changes in CRI were compared during key events, including hysterotomy, neonatal delivery, placental delivery, and postpartum recovery. Medications, vital signs, estimated blood loss (EBL) and fluid administration were recorded and analyzed.
Results: Seventy-four subjects, thirty-one vaginal and forty-three cesarean deliveries, had CRI values during key events and were analyzed. Vaginal delivery subjects trended towards lower median CRI values at delivery compared to cesareans, 0.35 (Interquartile range (IQR): 0.14, 0.5) and 0.74 (IQR: 0.5, 0.86) respectively (P<0.07). The changes in CRI from neonatal delivery to placental delivery were significantly different (P< 0.001) possibly representing the uteroplacental autotransfusion in vaginal deliveries with an increase in median CRI of 0.3 (IQR: 0.46, 0.02). Due to blood loss (median EBL was 250 ml and 800 ml), the median change in CRI from delivery to postpartum shows that vaginal deliveries return to slightly above predelivery CRI values 0.01 (IQR: -0.08, 0.08) while the CRIs of cesarean deliveries decrease by 0.05 (IQR: -0.04, 0.25). The overall decrease of CRI in cesarean delivery may be diminished because of the use of phenylephrine.
Conclusion: The Compensatory Reserve Index provides real-time, noninvasive, insight into hemodynamic and central volume changes associated with the exertion, uteroplacental autotransfusion and blood loss associated with delivery. Its effectiveness in assessing the central volume status of the mother during the peripartum period may prove useful for monitoring and improved resuscitation and care of the parturient.
 Pritchard JA: Changes in the blood volume during pregnancy and delivery. Anesthesiology. 1965; 26:393-399
 Kjeldsen J: Hemodynamic investigations during labor and delivery. Acta Obstet Gynecol Scand Suppl. 1979; 89:1-252
 Moulton S, Mulligan J, Santoro MA, Bui K, Grudic G, MacLeod D: Validation of a non-invasive monitor to continuously trend individual responses to hypovolemia. J Trauma Acute Care Surg 2017; 83(1 Suppl 1):104-111