Abstract 113

Blood lactate concentrations in critically ill adult patients can be used to detect tissue hypoxia, assess illness severity, and predict overall outcome. Recently, elevated initial postoperative blood lactate levels (>6 mmol/L) have been correlated with major adverse events in children following cardiac surgery. Therefore, we tested the hypothesis that blood lactate levels are predictive of early mortality in infants undergoing complex neonatal surgery for congenital heart disease. Serum bicarbonate, arterial and mixed venous oxygen saturation, and blood lactate were measured on admission, every 6 hours for the first 24 hours, and every 12 hours for a subsequent 2 days, in 27 consecutive patients who underwent cardiac surgery requiring cardiopulmonary bypass in the newborn period (less than 1 month of age). Twenty-one patients underwent the Norwood operation for hypoplastic left heart syndrome (HLHS), and six infants underwent a variety of other complex neonatal open heart operations. Results showed that initial postoperative blood lactate (mean±sem) was elevated in the non-survivor group (10.3±2.3 mmol/L, n=5) compared with the survivors (6.1±0.5 mmol/L, n=22), but this difference was not statistically significant (p=0.14). Initial postoperative lactate >6 mmol/L predicted mortality with sensitivity 80%, specificity 55%, and positive predictive value of only 29%. However, sequential measurements revealed that infants showing a consistent decrease or only a modest increase in blood lactate concentrations during the study period generally did well. In contrast, in all 5 neonates who did not survive, a significant rise in blood lactate concentrations (Δlactate/time≥0.75; p=0.0003) preceded death by more than two hours (sensitivity 100%, specificity 100%, positive predictive value 100%). Neither serum bicarbonate, nor arterial-mixed venous oxygen saturation difference was predictive of overall mortality in this patient population. We conclude that postoperative blood lactate is a significant independent predictor of impending mortality in infants undergoing neonatal repair/palliation for complex congenital heart disease, including HLHS.