[Perioperative assessment of blood lactate levels in pediatric heart surgery]

Abstract

Measuring arterial lactate concentration is a prompt, easy and relatively non-invasive way to estimate tissue oxygen metabolism. We evaluated whether perioperative levels of the arterial lactate concentrations can reflect the general severity of a pediatric patient's condition. A consecutive series of 112 patients, aged 5 days to 17 years (median age: 12 months), admitted to our pediatric intensive care unit (PICU) following cardiac surgery under cardiopulmonary bypass were studied. Arterial blood lactate concentration was measured preoperatively, immediately upon termination of the cardiopulmonary bypass (postCPB), immediately following the operation, and 16th hours postoperatively (D1). Trends within arterial lactate concentrations were examined in relation to mortality rates, the duration of PICU stays and the patient's ages. The studied population had a mortality rate of 5.7% (6 patients). Lactate levels increased significantly and exceeded 4.0 mmol.l-1 during postCPB measurements in a majority of the patients. The increases in lactate levels are affected by the changes in interorgan blood flow, blood glucose levels and/or blood pH in addition to the effects of the CPB-priming lactated Ringer's solution. Thus, higher cut off values have to be determined, and lower probabilities assigned, when using postCPB lactate levels to predict the severity of an outcome. Significantly and sustained increases in D1 lactate levels were noted in neonates, patients with longer PICU stays (> 15 days) and those died later. Hyperlactemia greater than 2.2 mmol.l-1 at D1 predicted death with a sensitivity of 82% and a specificity of 72%. The measurement of early postoperative lactate levels, reflecting postoperative ability to eliminate intraoperative hyperlactemia, is a better way of assessing the severity of a pediatric patient's condition following cardiac surgery. The ideal time to measure early postoperative lactate levels should be determined by further research.