Hyperlactataemia Following Crystalloid Cardiopulmonary Bypass Priming in Paediatric Cardiac Surgery—Is it Benign or Malignant?

Abstract

Introduction: There are various mechanisms leading to early hyperlactataemia (serum lactate >2 mmol/L) post-cardiac surgery. In children undergoing crystalloid priming of the cardiopulmonary bypass circuit, non-hypoxic mechanisms have been postulated to cause benign early hyperlactataemia. We sought to review patients who underwent crystalloid prime and assess their postoperative course, and whether their postoperative hyperlactataemia is truly benign. Methods: A retrospective review was performed of 186 patients who underwent cardiac surgery with crystalloid prime at our institution. Data were collected from medical and laboratory records. Results: Out of 186 patients, 98 (53%) had postoperative hyperlactatemia. The median age was 8.1 years (IQR, 4.7–12.8) and median weight was 23.6kg (IQR:17.1–46.0). The most common procedures were aortic valve/root procedures (n=42), septal defect closures (ASD/VSD/AVSD, n=41), and single-ventricle repairs (BCPC/Fontan, n=31). Overall, patients with postoperative hyperlactataemia had significantly longer ICU stays (p=0.003) and required significantly higher peak vasoinotropic support (VIS) within the first 24 hours (p=0.002). These patients underwent more complex procedures (higher Aristotle scores, cross-clamp and bypass times). However, of patients who had a normal postoperative course (ICU discharge ≤1 day), almost half (57/126) experienced hyperlactataemia, with no difference in VIS or Aristotle scores (p=0.15 and p=0.47, respectively). This suggests that elevated lactate levels in patients following crystalloid pump priming may represent a benign phenomenon but may also be a result of more complex conditions requiring longer support in ICU. Conclusions: Amongst patients having crystalloid prime, 31% (57/186) patients had benign hyperlactataemia. However, these patients need to be clinically distinguished from patients with hyperlactataemia from malignant mechanisms necessitating further intensive care or adaption of priming considerations.