Validation of bioimpedance estimates of cardiac output in preeclampsia.

Abstract

We sought to evaluate the capacity of a new thoracic electric bioimpedance system to estimate cardiac output in patients with preeclampsia. We performed a prospective comparison of thoracic electric bioimpedance and echocardiographic M-mode volumetric estimates of cardiac output (in liters per minute) in preeclampsia. Subjects with preeclampsia who were chosen by means of strict criteria (either a systolic blood pressure >/=140 mm Hg or a diastolic blood pressure 90 mm Hg, or both, and proteinuria >/=300 mg in 24 hours or >/=+1 on repeat dipstick measurement 6 hours apart) were asked to participate in an institutional review board-approved study. Thoracic electric bioimpedance and echocardiography were performed with the patients in the left lateral recumbent position. Thoracic electric bioimpedance estimates were recorded at bedside; investigators were blinded to 3 simultaneously obtained echocardiographic M-mode estimates of cardiac output. Means were entered as the estimate for each patient. To satisfy the assumption of independent samples, only 1 estimate from each technique was used for each patient. Data were analyzed by Bland-Altman comparison. Hemodynamic and demographic variables are presented as mean +/- SD. Fifteen patients were enrolled. Mean maternal age was 25.9 +/- 4.8 years, and mean gestational age was 34.0 +/- 3.5 weeks. Mean arterial pressure was 112 +/- 14 mm Hg. There was good agreement of thoracic electric bioimpedance-derived and M-mode-derived cardiac output estimates. In patients with preeclampsia, thoracic electric bioimpedance estimates of cardiac output compare well with echocardiographic M-mode estimates.