Evolution of early cerebral NIRS in hypoxic ischaemic encephalopathy

To describe early cerebral oxygenation (cSO₂ ) and fractional tissue oxygen extraction (FTOE) values and their evolution over the first days of life in infants with all grades of hypoxic-ischaemic encephalopathy (HIE) and to determine whether cSO₂ and FTOE measured early (6 and 12 h) can predict short-term outcome.

Prospective, observational study of cerebral near-infrared spectroscopy (NIRS) in infants >36 weeks' gestation with HIE. Ten one-hour epochs of cSO₂ and FTOE were extracted for each infant over the first 84 h. Infants with moderate and severe HIE received therapeutic hypothermia (TH). Abnormal outcome was defined as abnormal magnetic resonance imaging (MRI) and/or death.

Fifty-eight infants were included (28 mild, 24 moderate, 6 severe). Median gestational age was 39.9 weeks (IQR 38.1-40.7) and birthweight was 3.35 kgs (IQR 2.97-3.71). cSO₂ increased and FTOE decreased over the first 24 h in all grades of HIE. Compared to the moderate group, infants with mild HIE had significantly higher cSO₂ at 6 h (p = 0.003), 9 h (p = 0.009) and 12 h (p = 0.032) and lower FTOE at 6 h (p = 0.016) and 9 h (0.029). cSO₂ and FTOE at 6 and 12 h did not predict abnormal outcome.

Infants with mild HIE have higher cSO₂ and lower FTOE than those with moderate or severe HIE in the first 12 h of life. cSO₂ increased in all grades of HIE over the first 24 h regardless of TH status.