LACTATE AND PYRUVATE CHANGES IN THE CEREBRAL GRAY AND WHITE-MATTER DURING POSTHYPOXIC SEIZURES IN NEWBORN PIGS

Cerebral lactate rises after chemically induced seizures, but it is no t known if this occurs with posthypoxic seizures. We examined changes in lactate and pyruvate in gray and white matter in the newborn pig br ain after a hypoxic insult known to produce seizures and permanent bra in damage. Fourteen halothane-anesthetized piglets aged 24-49 h, were instrumented with a two-channel scalp EEG and microdialysis probes pos itioned in white and gray matter. Forty-five minutes of hypoxia were i nduced by reducing the fraction of inspired O-2 to the maximum concent ration at which EEG amplitude was <7 mu V. Postinsult EEG was classifi ed as electroconvulsive activity (ECA) (n = 4) or burst suppression (n = 2), persistently low amplitude (n = 2), or intermittent spikes on n ormal background activity (n = 6). Six hours after the insult the brai ns were perfusion fixed for histologic probe localization. Plasma lact ate and brain lactate had different time courses with brain having a p ersistently elevated lactate/pyruvate (L/P) ratio. The highest L/P rat ios in gray and white matter were in the two pigs with persistently lo w amplitude EEG. There was no association between onset of electroconv ulsive activity and an increase in lactate or L/P ratio. Posthypoxic e nergy metabolism is disturbed in both gray and white matter probably b ecause of mitochondrial dysfunction. Seizure activity does not increas e cerebral lactate or L/P ratio above the already raised levels found in posthypoxic encephalopathy. These findings cast further doubt on th e hypothesis that such seizures are, in themselves, damaging.