Background: This study aimed to investigate the effect of operative and postoperative parameters on late-onset hyperlactatemia (LOHL) after cardiac surgery in the pediatric patient population.Methods: One hundred fifty-nine ventricular septal defect patients (77 males, 82 females; mean age: 8.0±8.6 years; range, 1 to 48 years) were retrospectively examined between August 2020 and February 2023. Patients with the highest lactate value measured between 6 to 12 h postoperatively <3 mmol/L were defined as Group 1, and those with lactate values ≥3 mmol/L (LOHL) were included in Group 2.

Results: Cardiopulmonary bypass (CPB) time, aortic cross-clamp time, and CPB flow did not differ between groups (p=0.916, p=0.729, and p=0.699, respectively). The difference between partial oxygen pressure (PaO₂) in the first blood gas obtained after CPB was statistically significant (p=0.017). The lactate level measured in the first arterial blood gas obtained after CPB was 1.74±0.61 mmol/L in Group 1 and 3.01±1.63 mmol/L in Group 2 (p<0.001). The PaO₂ in the arterial blood gas measured at 6 h postoperatively was 129.22±61.20 mmHg in Group 1 and 156.07±64.49 mmHg in Group 2 (p=0.046).

Conclusion: The development of hyperlactatemia due to ischemia in the early post-CPB period may affect the development of LOHL. Microcirculatory changes at the tissue level may play a role in the etiology of LOHL.