Minimally Invasive Coronary Artery Bypass Grafting Reduces Postoperative Serum Lactate Level and Minimizes Associated Complications

Background: Postoperative lactate levels have been considered a marker of intraoperative ischemia, which can affect patients’ prognosis. This study aims to compare the immediate postoperative complications due to high serum lactate levels of patients who had undergone coronary artery bypass graft (CABG) via minimally invasive cardiac surgery (MICS) vs. conventional median sternotomy (MS). Methods: A total of 111 MICS CABG patients were retrospectively analysed and compared with 3614 MS CABG patients from a mixed Asian population between January 2009 and June 2020. A generalized structural equation model (gSEM) was constructed and applied for data analysis, with the primary outcome of this study being high postoperative serum lactate levels (≥4 mmol/L) and its associated complications. The model considered patients’ demographics, blood tests, Charlson co-morbidity index, and the type of operation. Results: There were no significant differences in the patients’ preoperative profiles. The average postoperative serum lactate level in both groups was 3.2 mmol/L (range: 0.5 to 15.6 mmol/L). MICS patients had significantly lower postoperative lactate levels (coefficient: −1.1; 95% C.I.: −1.8 to −0.4, p-value: 0.002). Moreover, a unit increase in lactate level was associated with a 12% increase in the odds of developing a new arrhythmia postoperatively (adjusted odds ratio: 1.1; 95% C.I.: 1.0 to 1.3, p-value: 0.048). Conclusion: MICS was associated with lower postoperative lactate levels and reduced metabolic stress, likely due to less trauma. Elevated lactate during CPB correlated with higher morbidity and mortality. Patients who are eligible for both approaches may benefit more from the MICS approach.