Traditional assessment of the cardiovascular patient may be inadequate to detect perfusion failure and those at risk for complications. Serum lactate has been correlated to outcome in adult shock states. We assessed the value of serum lactate measured following cardiac surgery in children.

METHODS: Arterial lactate levels were prospectively measured on admission to the Critical Care Unit(CCU) in 109 consecutive cardiac surgical patients(age 1day-19years) after cardiopulmonary bypass and cardioplegic arrest. Complicated outcomes(32/109) were defined as i) sternal opening in the CCU(15/32) ii) open sternum from the operating room(15/32) iii) death(8/32) iv) reoperation(5/32) v) cardiac catheterization(5/32) vi) extracorporeal membrane oxygenation(3/32) vi) cardiac arrest with resuscitation(1/32). Correlation of admission lactate levels to intraoperative and outcome variables was tested using multiple logistic regression analysis and Student's t-test.

RESULTS: Mean admission lactate in patients with complicated outcomes was 8.6±6.1 vs. 3.2±1.9 mmol/l in uncomplicated cases(p<0.0001). Lactate levels >5mmol/l were associated with 75% sensitivity and 84% specificity for complications. In the subgroup requiring total circulatory arrest, lactate was 9.8±6.5 (complicated n=23) vs. 5.4±2.2(uncomplicated n=22)(p<0.002). Nonsurvivors had significantly higher admission lactate levels as compared to complicated survivors(13.7±8.9 vs. 6.8±3.7, p<0.005). Lactate levels were correlated with duration of cardioplegic arrest, vasopressor supports, ventilator days, CCU length of stay and inversely correlated to age and weight(p=0.0001). Lactate was unrelated to arterial pH, bicarbonate or base excess.

CONCLUSIONS: Initial post operative lactate levels measured after open heart surgery in children are significantly related to complicated outcomes. This may reflect intraoperative tissue oxygen debt and postoperative perfusion failure that is not apparent by blood gas analysis alone.