Threshold of metabolic acidosis associated with neonatal encephalopathy in the term newborn

Abstract

Objective. To determine the threshold of metabolic acidosis associated with neonatal encephalopathy (NE) in the term newborn.Methods. Term patients were included on the basis of abnormal hemodynamic, respiratory or neurological signs still persisting 30 min after birth. Base deficit (BD30) was measured in arterial blood between the 30th and the 45th min of life and correlated with the occurrence of NE during the first days of life using receiver operating characteristics (ROC) methodology.Results. Moderate or severe NE occurred in 26% of patients whose BD30 was higher than 10 mmol/L and in 79% of patients whose BD30 was higher than 18 mmol/L. No infants developed moderate or severe NE when BD30 was less than 10 mmol/L. The apex of ROC curve related to moderate or severe NE corresponds to a BD30 of 14 mmol/L. At this threshold, the sensitivity of BD30 is 73.2% and the specificity 82%.Conclusion. The threshold of metabolic acidosis that provides the best combination of sensitivity and specificity in relation to the occurrence of moderate or severe NE was a BD30 higher than 14 mmol/L. Significant birth asphyxia should be considered if BD30 exceeds 10 mmol/L.