Background

Haemoglobin A1c (HbA1c) is an established measurement for the monitoring of long-term glycaemic control in patients diagnosed with Diabetes Mellitus (DM). It has also been suggested that HbA1c be used as a screening tool to identify patients previously undiagnosed with DM. A correlation between elevated preoperative HbA1c and postoperative complications following cardiac surgery is well supported, however evidence related to non-cardiac surgery is currently limited. Postoperative complications are associated with poorer prognosis, increased length of stay and greater hospital costs. 

Aim

To investigate whether there was a relationship between Haemoglobin A1c (HbA1c) and postoperative infectious complications requiring antibiotics following major elective surgery.

Method

Patients undergoing major elective surgery (including orthopedic, general surgery and vascular surgery) had their HbA1c taken within 30 days preoperatively, and were then followed up for 30 days postoperatively. Patients previously undiagnosed with DM with a HbA1c of >6.5% (48 mmol/mol) were notified. Significant variables were placed into multivariate binary logistic model. A nomogram was produced, displaying the relationship between HbA1c and the risk of surgical site infection (Figure 1).  A Roc curve analysis was performed to determine the efficiency of this model . 

Results

During the study period, 134 patients undergoing major elective surgery were recruited. This cohort consisted of 94 non diabetic patients, 38 diabetic patients, and two previously undiagnosed diabetic patients with a HbA1c of greater than 6.5% (48 mmol/mol). Elevated preoperative HbA1c had a positive association with postoperative surgical site infection (SSI) requiring antibiotics (p<0.016, OR 1.9, 95% CI 1.1 – 3.3). Body-Mass index > 35 (BMI>35) was also associated with increased SSI risk (p< 0.036, OR 3.1, 95% CI 1.1 – 9.0).

Discussion

Our study confirmed a correlation between elevated preoperative HbA1c and postoperative surgical site infections. In particular patients with a higher BMI are more at risk.  Further prospective evidence is required to determine if there is a correlation with other non-infectious complications and whether preoperative intervention to improve glycemic control would improve outcomes.

Correlations between HbA1c and complications following surgery – A prospective cohort study