Stroke volume and cardiac output evaluation by electrical cardiometry: accuracy and reference nomograms in hemodynamically stable preterm neonates

OBJECTIVE: To investigate the accuracy of electrical cardiometry (EC) to measure stroke volume (SV) and cardiac output (CO) and to provide gestational age (GA) and birth weight (BW)-based reference data for SV and CO in hemodynamically stable preterm neonates. STUDY DESIGN: Prospective observational blinded study. Paired measurements of SV and CO on stable preterm infants without any hemodynamic compromise were carried out using EC (SVEC) and echocardiography (SVECHO). RESULTS: Seventy-nine preterm neonates (mean GA: 31 +/- 3.2 weeks) were enrolled. A good correlation was found for SV (r = 0.743; P < 0.0001) and CO (r = 0.7; P < 0.0001) measured by EC and echocardiography. These correlations remained significant after adjusting for GA, patent ductus arteriosus and type of respiratory support (SV: St.beta = 0.48, P < 0.0001 and CO: st.beta = 0.69, P < 0.0001). Mean biases (and variabilities) were -1.1 (from 0.7 to -2.9) ml and -0.21 (from 0.15 to -0.55) I min(-1) for SV and CO, respectively. Local regression shows a tendency for EC to overestimate SV and CO especially at higher values (at about >2 ml and >0.41 min(-1), respectively). Coefficient of variation of SV was 48.9% and 52%, for EC and echocardiography. SV and CO rose with increasing GA and BW following an exponential equation (R-2>0.8). CONCLUSION: Measuring SV and CO with EC in hemodynamically stable preterm infants shows good correlation and variability similar to that of echocardiography. A trend to overestimation exists at highest values, but it is unlikely to be clinically significant. Reference GA and BW-based nomograms for SV and CO are provided.