Serial blood lactate levels as a predictor of mortality in children after cardiopulmonary bypass surgery

Abstract

Objective: To assess the role of serial lactate levels in determining outcome after cardiopulmonary bypass surgery in children.

Design: Analysis of retrospectively collected data.

Setting: Cardiac intensive care unit of a tertiary care children's hospital.

Patients: Patients were 129 children who underwent surgery for congenital cardiac defects.

Interventions: None.

Measurement and main results: Patients were categorized for disease severity using the Risk Adjustment for Congenital Heart Surgery method. Blood lactate levels were obtained at admission to the cardiac intensive care unit and then serially until they were <2 mmol/L. Lactime, time during which the lactate remains >2 mmol/L, was noted for each patient. The primary outcome measured was mortality. Secondary outcomes measured were ventilator days and hospital days. Six patients died, and of these five were neonates. Nonsurvivors had higher initial postoperative lactate concentration (p = .01), peak postoperative lactate concentration (p = .003), and lactime (p = .05). In binomial logistic regression analysis, lactime was the strongest predictor of mortality (p = .03). The positive predictive value for all age groups was highest for lactime >48 hrs, with a positive predictive value of 60%, and among the neonates it was 75%. Initial lactate level >6 mmol/L had a positive predictive value of only 6%, and the peak lactate level >6 mmol/L had a positive predictive value of only 15%. Lactime also had a significant association with ventilator days and hospital days among the survivors (p = .001).

Conclusions: Lactime was a useful predictor of mortality in children undergoing repair or palliation of congenital cardiac defects under cardiopulmonary bypass. Initial and peak lactate levels had a poor positive predictive value for mortality. Lactime also was associated with the number of ventilator days and hospital days in those who survived.