The clinical relevance of an elevated lactate level after surgery for congenital heart disease

Introduction

Lactate is a product of anaerobic glycolysis, and may be increased due to inadequate oxygen supply, excessive oxygen demand, liver failure or exogenous supply with blood products. Children after cardiothoracic operations may therefore be at risk for elevated lactate concentrations. We examined the impact of elevated lactate levels on postoperative outcome.

Method

The records of 253 children, aged 1 day to 17 years, who underwent open or closed cardiac surgery in our institution between March 1997 and May 1998, were examined retrospectively. Twenty children were excluded because of incomplete data sets. The postoperative concentration of lactate was measured at the time of admission to our intensive care unit and was related to intraoperative and postoperative data.

Results

Lactate concentrations for various durations of cardio-pulmonary bypass (CPB) are shown in Table 1. The mean lactate was 3.37 mmol/l on postoperative admission. In the 215 patients who survived, mean lactate was 2.8 (0.6-19.6) mmol/l, versus 10.6 (2.1-22.4) mmol/l in the 18 children who died during the postoperative period. In 10 children with multiple organ failure lactate was 9.8 (2.1-19.6) mmol/l, versus 3.1 (0.6-22.4) mmol/l in children without. In 23 children who suffered from neurological complications we found higher lactate (9.0 [1.0-22.4] mmol/l) than in 210 children without (2.8 [0.6-21.3] mmol/l). In the group of children with a lactate level greater than 6 mmol/l (n = 34) mortality was 41.1%, incidence of multiple organ failure was 14.7% and incidence of neurological complications was 44.1%. In contrast, in the group with lactate levels below 6 mmol/l (n = 199) mortality rate was 2.0%, incidence of multiple organ failure was 5% and incidence of neurological complications was 4.5%.

Table 1 Lactate concentrations

Conclusion

The concentration of lactate in the blood is higher after operations with CPB then after those without, and the level of lactate increases with the duration of CPB. The risk for postoperative morbidity and mortality is increased with higher lactate concentrations. Therefore, lactate concentration might be a valuable parameter during CPB and during the postoperative period.