Introduction: A history of diabetes has been associated with postoperative wound infection. Consecutively, it has been proposed that a low HgbA1c level should decrease the risk of postoperative wound infections. However to our knowledge the effect of an increased HgbA1c level on postoperative wound infection has not been published. We hypothesized that increased levels of HgbA1c are associated with increased surgical wound infections.
Methods: This study was approved by our institutional review board and was exempt from the consent process. Data from all surgical patients from a single institution were queried from January 2014 to December 2016. All patients who had preoperative HgbA1c data available (up to 3 months prior to surgery) were included. Patients with HgbA1c values less than 5.0 or greater than 20 were excluded. In the instance when patients had multiple surgeries, only the first encounter was included in the analysis. The outcome was 60-day postoperative wound infection, which was identified by the presence of this diagnosis code 60 days following surgery. Multivariable logistic regression was performed to determine if HgbA1c was associated with infection. The covariates in the model included surgical service, age, and gender.
Results: There were a total of 17,971 surgical patients included in the analysis after exclusion. Of these, there were 354 (2.0%) postoperative wound infections. The median preoperative hemoglobin A1c value was 5.8 [25-75% interquartile range 5.4, 6.3] and the range was 5.0 to 15.6. Univariable logistic regression analysis demonstrated that there was a 14% increased odds of 60-day postoperative wound infection for every one unit increase in HgbA1c after 5.0 (OR 1.14, 95% CI 1.07 – 1.22, p<0.0001). After adjusting for age, sex, and surgical specialty, the association was still significant (OR 1.11, 95% CI 1.04 – 1.18, p=0.005). The rate of postoperative wound infection in patients with HgbA1c >= 5.0 and < 7 was 1.87%; HgbA1c >=7 and <10 was 2.41%; and HgbA1c >=10 was 3.97%.
Conclusion: In this retrospective study we observed that an increase in the HgbA1c level was associated with a significant increase in postoperative wound infections. Further studies need to be completed to determine whether decreasing HgbA1c levels will result in a decrease in the postoperative wound infection rate.
