Birth Asphyxia. I. Measurement of Visual Evoked Potential (VEP) in the Healthy Fetus and Newborn Lamb

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Abstract
Summary: The visual evoked potential (VEP) of five healthy, near-term exteriorized fetal lambs was compared with the VEP obtained from the same animals during the first hour after ventilation. Characteristics of the individual wave components and their relationship to blood pressure, heart rate, and arterial blood gas measurements concomitantly obtained were examined. Results show that the VEP of the healthy fetus is a stable, reproducible signal consisting of four basic components, and that the latencies (msec) and the amplitude (μV) of the individual components of the VEP are similar to those of the newborn. In two related experiments, fetal asphyxia of unknown duration was encountered during fetal exteriorization and instrumentation. In the first case, neonatal acidosis persisted despite aggressive resuscitation efforts and was accompanied by an atypical VEP. In the second case, the neonatal VEP obtained after 15 min of resuscitation was markedly depressed despite restoration of acid-base balance but gradually recovered during the remainder of the 1-hr newborn period. In conclusion, the VEP is a reproducible measure of cortical function in the healthy fetus and neonate and may reflect the acute status of cerebral function during fetal asphyxia and neonatal resuscitation. Speculation: The initial success of neonatal resuscitation after birth asphyxia is predicated upon the response of blood pressure, heart rate and blood gas measurements, yet these measurements indicate only indirectly whether brain damage has occurred during asphyxia, or whether brain recovery is eminent. The visual evoked potential may provide a reproducible measure of the effectiveness of current resuscitation practices.