C reactive protein: impact on peripheral tissue oxygenation and perfusion in neonates.

Objective: C reactive protein (CRP) is a sensitive marker of acute inflammation of infectious and non-infectious origin. Aim was to use near-infrared spectroscopy (NIRS) to analyse peripheral oxygenation and perfusion in term and preterm neonates with elevated CRP levels, at a time when routine haemodynamic variables are still normal.

Design: Prospective observational study.

Settings: Peripheral-muscle NIRS was performed in the first week of life. Tissue-oxygenation index (TOI), mixed venous oxygenation (SvO(2)), fractional oxygen extraction (FOE), haemoglobin flow (Hbflow), oxygen delivery (DO(2)) and oxygen consumption (VO(2)) were assessed. Blood samples were taken within 3 h of the NIRS measurements.

Patients: Cardiocirculatory stable term and preterm neonates with infection-related and infection-unrelated CRP elevations >10 mg/l were compared with neonates without CRP elevation. The two groups were matched for gestational and postnatal age.

Results: 33 neonates with CRP elevation (gestational age 37.7±2.9 weeks) were compared with 33 controls (gestational age 37.3±2.9 weeks). In neonates with CRP elevation, TOI (68.9±6.6%), SvO(2) (66.9±7.3%) DO(2) (39.2±16.1 µmol/100ml/min) and VO(2) (10.9±3.4 µmol/100ml/min) were significantly lower compared with controls (TOI 72.9±3.8%, SvO(2) 70.2±4.7%, DO(2) 48.8±18.4 µmol/100ml/min, VO(2) 12.3±3.8 µmol/100ml/min). There was no significant difference in any other NIRS or routine haemodynamic parameter between the two groups.

Conclusion: Inflammatory processes with CRP elevation cause impaired peripheral oxygenation and perfusion in neonates even when routine haemodynamic variables are still normal. NIRS might offer a new non-invasive tool for the early recognition and diagnosis of infectious and non-infectious inflammatory processes.