The role of spectral edge frequency monitoring in neonatal intensive care

Abstract

Conventional multi-channel electroencephalograms (EEGs) may assist with outcome prediction in newborn infants, but are often logistically difficult and require specialist interpretation. Cotside EEGs using reduced numbers of electrodes generate quantitative parameters such as spectral edge frequency (SEF), but it is not yet clear if these are clinically useful. The aim of our studies was to test the hypothesis that SEF and other quantitative parameters obtained from two channel cotside EEGs in preterm infants and term infants at risk of seizures predict long-term neurodevelopmental outcome. We recruited 120 preterm infants <32 weeks gestation. SEF from early cotside EEGs did not predict outcome. However continuity measures were weakly related to motor development at 18 months. There were weak relationships between early quantitative neurophysiological parameters and early illness severity scores, cranial ultrasound scans and pre-discharge neurological examinations. A neurophysiologist reviewing the two channel raw EEG predicted outcome slightly more accurately than the continuity measures. In normal preterm infants there was a characteristic pattern of changes in EEG parameters after birth, with the SEF patterns suggesting delayed maturation in the most immature infants. Low cerebral blood flow and low blood pressure in the first 48 hours were associated with changes in EEG parameters that persisted for some hours after the cardiovascular perturbations. Surfactant administration and opiate boluses were associated with reduced EEG continuity. We recruited 24 term infants with, or at risk of, clinical seizures. The background amplitude-integrated (a)EEG pattern was the best EEG predictor of neurodevelopmental outcome. However, magnetic resonance imaging was a better predictor than either cotside or conventional EEG. When convalescent cotside and conventional EEGs were compared, there was moderate agreement between the neurophysiologist‟s report on the conventional EEG and the background pattern of the aEEG, but not between assessments of sleep state cycling. Our data suggest that two channel cotside EEGs are not clinically useful for outcome prediction in preterm infants, but can assist in term infants. Future software development may increase their clinical utility. Cotside EEGs may also provide useful information regarding changes in neurophysiology after birth, cerebral responses to clinical interventions and postnatal cortical maturation in preterm infants.