Comparisons of Continuous-wave Doppler Ultrasound Monitor and Echocardiography in Cardiac Postoperative Pediatric Patients

Rational and Objectives Non-invasive cardiac output (CO) measurements are essential during the immediate post-operative course of young, congenital heart repaired patients. The use of the Ultrasonic Cardiac Output Monitor (USCOM) in pediatric intensive care units (PICU) is increasing. The literature on accuracy of USCOM in young, critically ill, mechanically ventilated, hemodynamically supported patients is scarce. We aimed to assess agreement between the USCOM device and echocardiography for measurements of CO in this population. Materials (Patients) and Methods A prospective observational study in a pediatric cardiac intensive care unit (PCICU). Paired CO measurements were taken in young, mechanically ventilated, immediate post-operative patients with exclusion of unrepaired or residual intra-cardiac shunt, using USCOM and echocardiography, by two separate senior performers. Agreement between echocardiography and USCOM was assessed by percentage error and Bland-Altman analysis. Results One hundred and thirteen comparison scans were performed on 61 patients: mean age 94 +/- 111 d, weight 4.7 +/- 2.1 kg, vaso-inotropic score 15.3 +/- 11, and STAT score 3-4 (46%). Mean USCOM cardiac index (CI) percent difference was -9.6% (45.6) and velocity-time-integral (VTI) 8.9% (34.7). Bland-Altman analyzes demonstrated poor agreement comparing USCOM to echocardiography with regard to CI, stroke volume (SV), VTI and aortic diameter (AO) measurements. Conclusion Our study shows that USCOM underestimates CI in comparison with echocardiography; therefore USCOM should be used with great caution as an absolute estimate or surrogate of CI in neonates and infants in the immediate post-operative, congenital heart surgery period.