Continuous non-invasive measurement of cardiac output in neonatal intensive care using regional impedance cardiography: a prospective observational study

Abstract

Objectives: To compare agreement between echocardiography and regional impedance cardiography (RIC)-derived cardiac output (CO), and to construct indicative normative ranges of CO for gestational age groups.

Design, setting and participants: Prospective cohort observational study performed in a tertiary centre in London, UK, including neonates born between 25 and 42 weeks' gestational age.

Exposures: Neonates on the postnatal ward had 2 hours of RIC monitoring; neonates in intensive care had RIC monitoring for the first 72 hours, then weekly for 2 hours, with concomitant echocardiography measures.

Main outcomes and measures: RIC was used to measure CO continuously. Statistical analyses were performed using R (V.4.2.2; R Core Team 2022). RIC-derived CO and echocardiography-derived CO were compared using Pearson's correlations and Bland-Altman analyses. Differences in RIC-derived CO between infants born extremely, very and late preterm were assessed using analyses of variance and mixed-effects modelling.

Results: 127 neonates (22 extremely, 46 very, 29 late preterm and 30 term) were included. RIC and echocardiography-measured weight-adjusted CO were correlated (r=0.62, p<0.001) with a Bland-Altman bias of -31 mL/min/kg (limits of agreement -322 to 261 mL/min/kg). The RIC-derived CO fell over 12 hours, then increased until 72 hours after birth. The 72-hour weight-adjusted mean CO was higher in extremely preterm (424±158 mL/min/kg) compared with very (325±131 mL/min/kg, p<0.001) and late preterm (237±81 mL/min/kg, p<0.001) neonates; this difference disappeared by 2-3 weeks of age.

Conclusions: RIC is valid for continuous, non-invasive CO measurement in neonates. Indicative normative CO ranges could help clinicians to make more informed haemodynamic management decisions, which should be explored in future studies.

Trial registration number: NCT04064177.

Keywords: Cardiology; Intensive Care Units, Neonatal; Neonatology.