Non-invasive cardiac output assessment in critically ill paediatric patients.

OBJECTIVE: Recently, non-invasive methods for cardiac output (CO) assessment have been developed including the ultrasonic cardiac output monitor (USCOM). This technique uses the same concept as Doppler echocardiography but differs in two aspects including continuous wave (CW) Doppler and estimated outflow tract diameter (OTD) used in USCOM compared to pulsed wave Doppler and directed measurement of OTD used in echocardiography. We sought to assess the agreement between CO assessment by USCOM and echocardiography in critically ill paediatric patients.

METHODS: Paired measurements of CO in critically ill paediatric patients were simultaneously and independently obtained by USCOM and echocardiography. Agreement between OTD, velocity time integral (VTI), CO, and cardiac index (CI) were assessed by percentage error and Bland-Altman analysis.

RESULTS: Thirty-four children (aged 7.86 +/- 5.78years, 44.1% male) had a mean OTD (1.47 +/- 0.38, 1.41 +/- 0.40), VTI (19.13 +/- 6.06, 23.53 +/- 7.31 cm), CO (3.88 +/- 2.19,4.41 +/- 2.83 l/min) and CI (4.23 +/- 1.19,4.77 +/- 1.43 l/min/m2) by echocardiography and USCOM, respectively. Bias +/- precision and percentage of error of OTD, VTI, CO, and CI were -0.07 +/- 0.20 cm, 27.80%; -4.40 +/- 3.84 cm, 31.99%; -0.53 +/- 1.23 l/min, 54.66%; and 0.54 +/- 1.03 l/min/m2, 42.32%, respectively. The bias +/- precision and percentage error were more important in patients with septic shock (n = 16).

CONCLUSION: USCOM was an unreliable tool for absolute value measurement of CO and CI due to the errors of VTI by CW Doppler.