Association of Elevated Pre-operative Hemoglobin A1c and Post-operative Complications in Non-diabetic Patients: A Systematic Review

Importance Pre-operative hyperglycemia is associated with post-operative adverse outcomes in diabetic and non-diabetic patients. Current pre-operative screening includes random plasma glucose, yet plasma glycated hemoglobin (HbA1c) is a better measure of long-term glycemic control. It is not clear whether pre-operative HbA1c can identify non-diabetic patients at risk of post-operative complications. Objective The systematic review summarizes the evidence pertaining to the association of suboptimal pre-operative HbA1c on post-operative outcomes in adult surgical patients with no history of diabetes mellitus. Evidence review A detailed search strategy was developed by a librarian to identify all the relevant studies to date from the major online databases. Findings Six observational studies met all the eligibility criteria and were included in the review. Four studies reported a significant association between pre-operative HbA1c levels and post-operative complications in non-diabetic patients. Two studies reported increased post-operative infection rates, and two reported no difference. Of four studies assessing the length of stay, three did not observe any association with HbA1c level and only one study observed a significant impact. Only one study found higher mortality rates in patients with suboptimal HbA1c. Conclusions and relevance Based on the limited available evidence, suboptimal pre-operative HbA1c levels in patients with no prior history of diabetes predict post-operative complications and represent a potentially modifiable risk factor.