Prediction of seizures in asphyxiated neonates: Correlation with continuous video-electroencephalographic monitoring

BACKGROUND. After perinatal asphyxia, predicting which infants will develop significant hypoxic-ischemic encephalopathy and neonatal seizures remains a difficult task. High-risk markers ( Apgar score, acidosis, nucleated red blood cells, and resuscitation) have been used to predict neonatal seizures with varying success. The "3 strikes" of Apgar score of < 5 at 5 minutes, pH < 7.00, and need for intubation have been cited as having a positive predictive value of 80%. We examined whether the predictive values of these markers would be increased if early continuous electroencephalographic monitoring allowed us to accurately identify all neonatal seizures and to grade the encephalopathy. METHOD. We recruited term infants with perinatal asphyxia. Continuous video electroencephalography was commenced soon after birth and continued for 24 to 72 hours. The abilities of high-risk markers to predict electroencephalographic seizurs, background electroencephalographic activity, and Sarnat grade were examined. RESULTS. Forty-nine infants were suitable for analysis. Electrographic seizures occurred in 11 of the 49 infants. Encephalopathy was scored by using Sarnat grade ( 6, severe; 18, moderate; 25, mild) and electroencephalographic findings ( 4 inactive, 4 major abnormalities, 16 moderate abnormalities, and 25 normal/mildly abnormal). Apgar score of < 5 at 5 minutes, pH < 7.0, and the need for intubation had positive predictive values for neonatal seizures of 18%, 16%, and 21%, respectively. Combining these markers gave a positive predictive value of 25% and a negative predictive value of 77%. Substituting base deficit or lactate for pH in the 3-strikes model did not improve its predictive value. Apgar score of < 5 at 5 minutes, nucleated red blood cells, and a base deficit less than - 15 mEq/L showed some association with Sarnat grade. Only 5-minute Apgar score was significantly associated with both Sarnat grade and electroencephalographic grade. CONCLUSION. After perinatal asphyxia, neither the condition at birth nor the degree of metabolic acidosis reliably predict neonatal seizures.