Background. Elevated lactate levels are commonly encountered in patients after heart surgery secondary to lactic acid production or lactic acidosis due to tissue hypoperfusion and hypoxia during the operation. It provides an important prognostic marker in critically ill patients. This study aims to utilize serial lactate level determinations in predicting major adverse events in children post open heart surgery.
Methods. Sixty-one (61) pediatric patients who underwent open heart surgery from May to October 2009 were recruited to participate in this prospective cohort study. Blood lactate levels were determined at 4 observational periods: immediately post bypass, 6th, 12th, and 24th hours after surgery. These levels were correlated with outcome (mortality, inotropic score, duration of intubation and ICU stay) and risk factors (bypass and cross clamp time, lowest temperature on bypass). Cut-off level at each observation period was determined using ROC curve, kappa coefficient, sensitivity, specificity and predictive values.
Results. In this cohort study, mean age of the participants was 7.02 years old, 54% were males and 25 underwent VSD closure. Average bypass and cross clamp time was 120.88 and 81.24 minutes respectively. Post-operative lactate levels correlated significantly with the different outcome measures. The immediate post operative lactate level had correlation with duration of cardiopulmonary bypass; whereas, the 6th hour determination of lactate level was correlated with the lowest temperature on bypass. Analysis of eo-variance reported that the lactate levels immediately and 6th hour postoperatively is associated with mortality (p<0.001 and p<0.001 respectively). Trends toward association between 24th hour lactate level and prolonged intubation as well as composite outcome and immediate post operative lactate levels were also established. The following cut-off lactate levels were as follows: <!:6 immediate post operatively, <!:4 at 6th hour, <!:2.5 at 12th hour, and <!:24th hours post operatively.
Conclusion. Numerous studies have documented the significance of lactate level in predicting mortality and morbidity in pediatric heart surgery. With the initial cut off lactate levels determined by this study at four different observation periods and with just a few cardiac centers capable of doing heart surgery, a large, prospective, preferentially multiple institutional trial be conducted in order to clearly established levels predictive of outcome in congenital cardiac surgery in the country.