Serum lactate as a predictor of mortality after paediatric cardiac surgery.

Abstract

To assess the value of sequential lactate measurement in predicting postoperative mortality after surgery for complex congenital heart disease in children. Prospective observational study. Sixteen bedded paediatric intensive care unit (PICU). Ninety nine children (90 survivors, nine non-survivors). Serum lactate and base deficit were measured on admission and every six hours thereafter. Data were analysed by Mann-Whitney and Fisher's exact tests. There was considerable overlap in initial lactate values between the survivor and non-survivor groups. Initial lactate was significantly raised in non-survivors (median 8.7, range 1.9-17.6 mmol/l) compared with survivors (median 2.4, range 0.6-13.6 mmol/l) (p = 0.0002). Twenty one patients (21.1%) with initial lactate concentrations greater than 4.5 mmol/l survived to PICU discharge. Using receiver operating characteristic analysis an initial lactate of 6 mmol/l had the optimum predictive value for mortality. Initial postoperative serum lactate > 6 mmol/l predicted mortality with sensitivity 78%, specificity 83%, and positive predictive value of only 32%. Initial lactate concentrations have poor positive predictive value for mortality. The routine measurement of lactate for this purpose cannot be justified in clinical practice.