Measurement of visual evoked potential in the asphyctic fetus and during neonatal survival

Visual evoked potentials were measured in eight exteriorized near-term fetal lambs prior to and during 8 minutes of asphyxia and during 1 hour of newborn survival. Four of the lambs were then extubated, and measurements were continued while the lambs were observed for behavior and gross motor function. Early in the asphyctic period, marked changes in the visual evoked potential occurred in association with a fall in Po2, whereas during the postexposure period the visual evoked potential appeared to recover independently of cardiovascular or arterial blood gas values. Moreover, early wave components of the visual evoked potentials were more resistant to asphyxia than were later components and responded more quickly to resuscitative efforts. During the survival period the visual evoked potential did not correlate with gross motor function when animals were exposed to moderate acidosis. After severe acidosis abnormal visual evoked potentials were seen during periods of clinical deterioration.