Sugar, surgery, and survival: the impact of HbA1c on coronary artery bypass grafting recovery

Coronary artery bypass grafting (CABG) is a life-saving procedure for patients with severe coronary artery disease (CAD), effectively restoring blood flow to the heart and reducing ischemic symptoms[1]. However, CABG, especially when performed using cardiopulmonary bypass (CPB), carries the risk of various postoperative complications, such as acute kidney injury (AKI), infections, and extended stays in intensive care units (ICUs).[2-4] Identifying modifiable risk factors before surgery is critical to improving outcomes, particularly for patients with underlying conditions like diabetes. Poor glycemic control, reflected by elevated levels of glycated hemoglobin (HbA1c), is associated with increased risk of postoperative complications in patients undergoing CABG[5,6]. Elevated HbA1c, indicative of chronic hyperglycemia, predisposes patients to inflammation, oxidative stress, and endothelial dysfunction, contributing to poor healing and increased susceptibility to organ damage[7,8]. A recent study by Liu et al investigated the impact of preoperative HbA1c levels on postoperative complications in 98 patients undergoing CABG[9]. The patients were divided into three groups based on their HbA1c levels: those with low HbA1c (<5.7%), medium HbA1c (5.7–7.0%), and high HbA1c (>7.0%). The study found that patients in the high HbA1c group had significantly longer ICU stays and higher rates of AKI compared to the other groups (P < 0.05), despite similar surgical factors such as the number of bypass grafts and ventilation times. These findings suggest that poor glycemic control, reflected by elevated HbA1c levels, increases the risk of renal complications and prolonged ICU care following CABG. Hyperglycemia during and after cardiac surgery is known to exacerbate ischemia-reperfusion injury, amplify inflammatory responses, and impair wound healing.[10-12] Multiple studies have confirmed that elevated HbA1c levels before surgery are associated with higher rates of postoperative infections, prolonged ICU stays, and increased mortality[7,11,13,14]. Even minor increases in serum creatinine post-surgery have been linked to worse outcomes, emphasizing the critical role of preoperative blood glucose management[15,16]. Effective management of glycemic levels prior to surgery is crucial for reducing the risk of postoperative complications. For patients with poorly controlled diabetes or elevated HbA1c levels, optimizing glucose control through intensive insulin therapy or oral hypoglycemic agents before surgery can mitigate these risks.[17-19] Preoperative strategies may also include delaying elective surgery until glycemic control is improved to minimize the likelihood of complications like AKI and extended ICU stays. Intraoperative glycemic management is equally important, with studies demonstrating that tight glucose control during surgery, typically through the use of continuous insulin infusions, can improve postoperative outcomes.[20-22] Maintaining glucose levels within a target range (140–180 mg/dL) during CABG has been shown to reduce rates of infections, renal dysfunction, and other postoperative complications[22,23]. Postoperatively, continued monitoring and management of blood glucose levels are essential to maintaining these improvements and preventing complications related to hyperglycemia. Moving forward, more research is needed to establish optimal preoperative HbA1c thresholds that can minimize postoperative risks and improve outcomes in cardiac surgery. Additionally, perioperative management strategies that combine glucose control with real-time monitoring of other vital parameters, such as renal function and hemodynamics, could further reduce complication rates in high-risk populations. The introduction of continuous glucose monitoring systems (CGMS) during and after surgery may provide a more accurate assessment of glucose levels, allowing for real-time adjustments in insulin therapy and other interventions[24]. These advancements could help reduce the burden of postoperative complications, particularly in diabetic patients undergoing complex surgeries like CABG. In conclusion, Preoperative glycemic control plays a critical role in determining postoperative outcomes in patients undergoing CABG. By integrating HbA1c monitoring into preoperative assessments and employing intensive glycemic control strategies, healthcare providers can significantly reduce the risk of postoperative complications, improve patient recovery, and enhance overall outcomes in cardiac surgery.