‘Multi-associations’: predisposed to misinterpretation of peripheral tissue oxygenation and circulation in neonates

Abstract

Interpretation of peripheral circulation in ill neonates is crucial but difficult. The aim was to analyse parameters potentially influencing peripheral oxygenation and circulation. In a prospective observational cohort study in 116 cardio-circulatory stable neonates, peripheral muscle near-infrared spectroscopy (NIRS) with venous occlusion was performed. Tissue oxygenation index (TOI), mixed venous oxygenation (SvO2), fractional oxygen extraction (FOE), fractional tissue oxygen extraction (FTOE), haemoglobin flow (Hbflow), oxygen delivery (DO2), oxygen consumption (VO2), and vascular resistance (VR) were assessed. Correlation coefficients between NIRS parameters and demographic parameters (gestational age, birth weight, age, actual weight, diameter of calf, subcutaneous adipose tissue), monitoring parameters (heart rate, arterial oxygen saturation (SaO2), mean blood pressure (MAP), core/peripheral temperature, central/peripheral capillary refill time) and laboratory parameters (haemoglobin concentration (Hb-blood), pCO2) were calculated. All demographic parameters except for Hbflow and DO2 correlated with NIRS parameters. Heart rate correlated with TOI, SvO2, VO2 and VR. SaO2 correlated with FOE/FTOE. MAP correlated with Hbflow, DO2, VO2 and VR. Core temperature correlated with FTOE. Peripheral temperature correlated with all NIRS parameters except VO2. Hb-blood correlated with FOE and VR. pCO2 levels correlated with TOI and SvO2. The presence of multiple interdependent factors associated with peripheral oxygenation and circulation highlights the difficulty in interpreting NIRS data. Nevertheless, these findings have to be taken into account when analysing peripheral oxygenation and circulation data.