Physicians’ Estimates of Cardiac Index and Intravascular Volume Based on Clinical Assessment Versus Transesophageal Doppler Measurements Obtained by Critical Care Nurses

Abstract

To compare physicians' estimates of cardiac index and intravascular volume with transesophageal Doppler measurements obtained by critical care nurses, to assess the overall safety of transesophageal Doppler imaging by critical care nurses, and to compare hemodynamic measurements obtained via transesophageal Doppler imaging with those obtained via pulmonary artery catheterization. Data were collected prospectively on 106 patients receiving mechanical ventilation. Physicians estimated cardiac index and intravascular volume status by using bedside clinical assessment; critical care nurses, by using transesophageal Doppler imaging. In 24 patients, Doppler measurements were obtained within 6 hours of placement of a pulmonary artery catheter and recording of cardiac output and pulmonary artery occlusion pressure. With Doppler measurements as the reference, physicians correctly estimated cardiac index in 46 (43.8%) of 105 patients, underestimated it in 24 (22.9%), and overestimated it in 35 (33.3%). They correctly estimated volume status in 31 patients (29.5%), underestimated it in 16 (15.2%), and overestimated it in 58 (55.2%). Doppler measurements of cardiac output correlated with those obtained via pulmonary artery catheterization (r = 0.778; P < .001). Two patients had minor complications: dislodgement of a nasogastric tube and inability to obtain a Doppler signal. Physicians' assessment of cardiac index and intravascular volume in patients receiving mechanical ventilation is correct less than half of the time. Transesophageal Doppler imaging by critical care nurses appears to be a safe method for measuring cardiac index and estimating intravascular volume. Measurements obtained via Doppler imaging correlate well with those obtained via pulmonary artery catheterization.