The Relevance of Optimal Preoperative Glycemic Control for Outcomes of Patients with Diabetes Undergoing Surgery

OBJECTIVE: To investigate the association between glycemic control, measured by glycated hemoglobin (HbA1c) levels, and post-operative complications across various procedures, identify the prevalence of patients with undiagnosed prediabetes or diabetes undergoing surgery, and explore whether better glycemic management is associated with reduced short-term postoperative complications. BACKGROUND: The presence of diabetes and the level of long-term glycemic control, as measured using HbA1c, can influence perioperative morbidity and mortality. Current evidence is largely based on small, single-center studies, with heterogeneous analysis strategies. METHODS: Data from the 2021-2022 multi-institutional American College of Surgeons National Surgical Quality Improvement Program (ACS-NSQIP) were utilized. Adult patients with recorded HbA1c were selected and categorized into eight groups based on the presence of a diabetes diagnosis and their HbA1c values. Various preoperative, surgical, and postoperative variables were extracted and analyzed using multivariate regression models. RESULTS: The study included 502,478 patients with recorded HbA1c. Among those diagnosed with diabetes (n=179,697; 35.8%), HbA1c levels were distributed as follows: 27,516 (5.5%) had HbA1c <6% (<42 mmol/mol), 63,644 (12.7%) had HbA1c 6-6.9% (42-52 mmol/mol), 45,534 (9.1%) had HbA1c 7-7.9% (53-63 mmol/mol), 19,985 (4.0%) had HbA1c 8-8.9% (64-74 mmol/mol), and 23,018 (4.6%) had HbA1c ≥9% (≥75 mmol/mol). Of the patients without a diabetes diagnosis (n=322,781; 64.2%), 91,097 (18.1% of total) had HbA1c in the prediabetes range (5.7-6.4%, 39-46 mmol/mol) and 25,818 (5.1% of total) in the diabetes range (>6.4%, ≥47 mmol/mol). Multivariate logistic analysis revealed that, compared to patients without prediabetes or diabetes, patients with undiagnosed prediabetes had a lower risk of surgical complications, while patients with undiagnosed diabetes had a higher risk of medical complications. Patients with diagnosed diabetes with near-normal glycemia and those with very poor glycemic control had higher odds of any complication. Patients with undiagnosed prediabetes and undiagnosed diabetes had significantly lower chances of transfusion. Patients with undiagnosed diabetes and patients with diagnosed diabetes with near-normal glycemia, suboptimal glycemic control, or very poor glycemic control had significantly longer hospital stays compared to patients without prediabetes or diabetes. CONCLUSIONS AND RELEVANCE: Glycemic control significantly impacts morbidity and mortality in surgical patients. A total of 23% of patients were patients with undiagnosed prediabetes or diabetes, underscoring the importance of preoperative HbA1c screening for all patients. Both very low and very high HbA1c levels should be preoperatively addressed, with moderate control (HbA1c 7-8%, 53-64 mmol/mol) identified as optimal. Overall, these findings emphasize the need for personalized diabetes management plans tailored to each patient's needs and should inform clinical guidelines.