SLR - July 2020 - Tyler May

The Association of Preoperative Haemaglobin A1c with 30-day Postoperative Surgical Site Infection Following Non-Cardiac Surgery

Reference: Gabriel RA, Hylton DJ, Burton BN, Schmidt, UH, Waterman RS. The Association of Preoperative Haemoglobin A1c with 30-Day Postoperative Surgical Site Infection Following Non-Cardiac Surgery.  Journal of Perioperative Practice, 2019 Nov 7; 1750458919886183.

Scientific Literature Review

Reviewed By: Tyler May, DPM
Residency Program: Detroit Medical Center – Detroit, MI

Podiatric Relevance: It is well appreciated that patients with poorly controlled blood glucose levels are more likely to have postoperative complications. Given the prevalence of diabetes in the podiatric medicine and surgery patient population, it is important to consider a patient’s haemoglobin A1c (HbA1c) as part of their standard preoperative workup. The article being reviewed is a retrospective study that focused on the relationship between patient’s preoperative HbA1c and 30-day postoperative surgical site infections (SSI), which could assist in developing guidelines for optimizing diabetic patients for surgery. 

Methods: A retrospective study was performed that measured 30-day SSI as its primary outcome including four cohorts with HbA1c <6.5 percent, 6.5 percent to <8.0 percent, 8.0 percent to <10.0 percent, and greater than or equal to 10.0 percent. They used data for all patients that underwent vascular, orthopedic, or general surgery over a two-year period at their institution with a preoperative HbA1c obtained at least one year prior to surgery. Only patients with a preoperative HbA1c greater than or equal to 5.0 and less than 20.0 were included. Subjects were also required to have a preoperative diagnosis of type 2 diabetes and additional surgical encounters for the same patient were removed. SSI was defined by the presence of an associated ICD 9 or ICD 10 code for surgical site infection. A variety of secondary variables also evaluated including age, BMI, and surgical specialty. 

Results: There were a total of 3064 patients that underwent vascular, orthopedic, or general surgery meeting their inclusion criteria. Overall, the rate of 30-day SSI was 2.42 percent among the entire population. To compare the four separate cohorts, the rate of infection was 1.80 percent for patients in their reference group with HbA1c <6.5 percent, 3.52 percent for patients with HbA1c 6.5-8.0 percent, 4.60 percent for patients with HbA1c 8.0-10 percent, and 5.08 percent for patients with HbA1c >10.0 percent. Of the secondary variables evaluated, statistical significance for increased risk of 30-day SSI was associated with vascular surgery specialty, dementia, and history of chronic obstructive pulmonary disease. 

Conclusions: The statistical analysis showed that once a patient’s preoperative HbA1c was >8.0 percent, there was a two to three times greater likelihood of developing SSI relative to the reference cohort with a HbA1c <6.5 percent. This article emphasizes the importance of glucose level control in patients undergoing non-cardiac surgery and HbA1c values should be obtained as part of the preoperative workup. Particularly when scheduling elective surgeries, if a patient’s HbA1c is >8.0 percent, optimizing glycemic control should be seriously considered podiatric surgeons.  

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