///2013 Abstract Details
2013 Abstract Details2019-08-02T16:57:45-05:00

Increase in cardiac output due to autotransfusion during labor can be demonstrated by electrical cardiometry

Abstract Number: F 5
Abstract Type: Original Research

Thomas L Archer MD, MBA1 ; Jerasimos Ballas MD, MPH2; Kristin Mantell MD3; Timothy Maus MD4; Byron Fergerson MD5; Kristen Buono MD6

Aortocaval compression (AC) by the pregnant uterus can be harmful to mother and fetus both antepartum and during labor. It reduces uterine artery pressure and placental perfusion and causes uterine venous congestion. Despite such potential harm, there are few methods of detecting AC, other than by observing a decrease in maternal brachial blood pressure or fetal bradycardia. Electrical cardiometry (EC) calculates maternal cardiac output (CO) in a continuous and non-invasive manner. We hypothesize that a reduction in maternal CO serves as a proxy for AC, since decreased venous return will decrease CO. Conversely, a non-compressed vena cava will allow increased venous return and CO. Figure 1 shows simultaneous recordings of intrauterine pressure, CO by EC (the moving average over the last 10 cardiac cycles, recorded every 10 seconds), and instantaneous CO (stroke volume for a single contraction multiplied by instantaneous heart rate) by transthoracic echocardiography (TTE) using the LVOT/VTI method in a laboring patient at term. The patient was in pain-free labor under epidural analgesia and was positioned with approximately 45 degrees of left lateral tilt. A periodic increase in CO following each uterine contraction is observed with both TTE and EC. The simplest explanation for these periodic increases in CO is autotransfusion of blood out of the contracting uterus into the systemic circulation, in the presence of an unobstructed inferior vena cava. While absolute values for CO differ between the two methods, there appears to be a significant correlation in the trends, suggesting that EC may be a non-invasive and continuous method for detecting changes in CO in pregnant patients. Changing maternal position during labor under epidural analgesia often reduces the baseline CO as measured by EC and eliminates the “autotransfusion waves” of increased CO shown in Figure 1, suggesting the presence of AC when the patient is moved into a sub-optimal position. Detection of previously unrecognized AC may help guide antepartum and intrapartum management, leading to improved maternal and fetal outcomes.

SOAP 2013