Non-invasive cardiac output monitoring in neonates using bioreactance: a comparison with echocardiography.

OBJECTIVES: Non-invasive cardiac output monitoring is a potentially useful clinical tool in the neonatal setting. Our aim was to evaluate a new method of non-invasive continuous cardiac output (CO) measurement (NICOM™) based on the principle of bioreactance in neonates.

METHODS: In this prospective observational study, 10 neonates underwent 97 paired NICOM and echocardiography (echo) assessments of left ventricular output (LVO). For each neonate, NICOM measurements of left ventricular stroke volume (SV) and LVO over a 2- to 4-hour period were correlated with blinded, simultaneous, discrete echo measurements of SV and LVO. The precision and accuracy of the NICOM monitor relative to echo during periods of steady state were assessed.

RESULTS: The infants' median birth weight was 2.72 kg (IQR 1.56-3.23 kg, range 1.44-4.00) and their median gestation was 37 weeks (IQR 31-40 weeks, range 31-41). Median NICOM SV and LVO readings were consistently lower than echo (2.6 ml [IQR 1.4-3.2, range 0.6-5.3] vs. 3.5 ml [IQR 2.1-4.4, range 1.1-6.8], and 400 ml/min [IQR 233-476] vs. 559 ml/min [IQR 386-652], p < 0.001). The NICOM LVO readings were lower than the echo readings by a mean of 153 ± 56 ml/kg. NICOM consistently under-read LVO by 31 ± 8%, and this systematic difference was constant across the range of LVOs obtained. There was a strong correlation between NICOM and echo measurements of LVO (r = 0.95, p < 0.001).

CONCLUSION: Non-invasive cardiac output monitoring is feasible in neonates. Further validation studies in neonatal animal experimental models and human neonates need to be conducted before routine clinical use.