Impact of preoperative haemoglobin A<sub>1c</sub> levels on postoperative outcomes in adults undergoing major noncardiac surgery: A systematic review
Abby Yu, Quynh A. Truong, Karen Whitfield, Andrew T. Hale, Meng‐Wong Taing, Natalie Barker, Michael C dʼEmden
Abstract
Abstract Aims Diabetes is known to increase morbidity and mortality after major surgery. However, literature is conflicting on whether elevated preoperative haemoglobin A 1c (HbA 1c ) levels are associated with worse outcomes following major noncardiac surgery. We aimed to investigate the effect of incremental preoperative HbA 1c levels on postoperative outcomes in adults who had undergone major noncardiac surgery. Methods We systematically searched PubMed, EMBASE and the Cochrane Library databases for eligible studies published between January 2012 and July 2023. Randomised controlled trials and observational studies (cohort and case–control studies) which measured HbA 1c within 6 months before surgery and compared outcomes between at least three incremental subgroups or analysed HbA 1c as a continuous variable were included. The systematic review protocol was registered with PROSPERO (CRD42023391946). Results Twenty observational studies investigating outcomes across multiple surgical types were included. Higher preoperative HbA 1c levels were associated with increased odds of overall postoperative complications, postoperative acute kidney injury, anastomotic leak, surgical site infections and increased length of stay. Each 1% increase in preoperative HbA 1c was associated with increased odds of these complications. No association with reoperations and 30‐day mortality was identified. The literature was highly variable with respect to composite major complications, perioperative cardiovascular events, hospital readmissions, postoperative pneumonia and systemic thromboembolism. Conclusions Current evidence suggested that higher preoperative HbA 1c levels were associated with increased odds of postoperative complications and extended length of stay in adults undergoing major noncardiac surgery. Further high‐quality studies would be needed to quantify the risks posed and determine whether early intervention improves outcomes.