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.