Lack of Variability in Cerebral Oximetry Tendency in Infants with Severe Hypoxic–Ischemic Encephalopathy Under Hypothermia

Abstract

Cerebral oximetry using near-infrared spectroscopy (NIRS) provides continuous, noninvasive assessment of the degree of hemoglobin saturation of the brain tissue. Previous studies suggest that high values of regional cerebral tissue oxygen saturation (rScO₂) during the first days in neonates with significant hypoxic–ischemic encephalopathy (HIE) are correlated with an adverse neurological outcome. However, the results are not consistent among the studies. To examine the correlation of rScO₂ values and their variability over time with HIE severity, amplitude integrated electroencephalography (aEEG) background and seizure activity, neuron-specific enolase levels in cerebrospinal fluid, magnetic resonance imaging (MRI) findings, and neurological outcome. Retrospective study that included all consecutive infants with moderate-to-severe HIE born at ≥35 weeks gestational age admitted between January 2011 and December 2014. NIRS monitoring was initiated at admission and maintained during therapeutic hypothermia up to 12 hours after rewarming. To analyze rScO₂, different periods (0–6, 6–24, 24–48, 48–72, and 72–100 hours of life) and three ranges (<55%, 55–90%, >90%) were considered. Variability in each patient was considered ≤5% when changes in rScO₂ values in all periods were ≤5%. Twenty-three newborns were included. Infants who suffered from severe HIE, seizures, abnormal aEEG background, altered MRI or death, and abnormal outcome had rScO₂ values >90% and with less variability (≤5%). rScO₂ values >90% and a lack of variability over time in infants with HIE during cooling provide useful information about the severity of neurological status.