Impact of Pre-operative Hemoglobin A1C Level and Microbiological Pattern on Surgical Site Infection After Cardiac Surgery

Glycosylated Hemoglobin (HbA1C) as a Predictor of Early Postoperative Outcomes After Coronary Artery Bypass Grafting: A Single-Center Observational Study

Background Diabetic patients present a majority of patients undergoing surgical revascularization. Hyperglycemia is associated with increased adverse events. Glycosylated hemoglobin (HbA1c) is an effective biological marker for long-term glycemic control. As a result, there is an increased trend in its use as a predictor of adverse outcomes. This study aims to assess the impact of elevated HbA1c on the occurrence of postoperative complications after coronary artery bypass grafting (CABG). Methods We conducted a retrospective review of medical records from January 2015 to December 2022 for adult patients who underwent isolated CABG. We assessed patient demographics, medication, laboratory results, HbA1c results, and clinical data. The separate statistical models were designed to assess the predictors for the development of postoperative complications.  Results This retrospective single-center study was conducted on 289 consecutive adult patients who underwent on-pump CABG. Patient demographics showed that uncontrolled HbA1c was more in females (p=0.022), and hemodialysis patients (p=0.018). Across different levels of HbA1C, there were no significant differences in terms of the incidence of postoperative complications (p=0.788 for infection, p=0.372 for the need for blood transfusion, p=0.721 for heart failure, p=0.692 for arrhythmia, and p=0.712 for death). HbA1c had no predictive value for postoperative complications as indicated by multivariate and stepwise analysis in a separate model for each complication with receiver operator characteristics curves of each model showing similar strength of both multivariate and stepwise models. Conclusions In our data, elevated preoperative HbA1c had no predictive value for early complications and intermediate postoperative outcomes. We recommend that surgery should proceed without delay, even if patients have elevated HbA1C levels. As for elective patients with low-risk features and anatomy, optimizing preoperative glycemic control can be considered.

Preoperative hemoglobin A1c and perioperative blood glucose in patients with diabetes mellitus undergoing spinal cord stimulation surgery: A literature review of surgical site infection risk

AIMS

The aim of our study was to review the surgical literature regarding the relationship between hemoglobin A1c (HbA1c), diagnosis of diabetes mellitus (DM), and risk of postoperative surgical site infection (SSI).

METHODS

A librarian-assisted literature search was performed with two goals: (1) identify surgical publications related to SSI and HbA1c values, and (2) identify publications reporting infection risk with DM in spinal cord stimulation (SCS), intrathecal drug delivery systems (IDDS), and cardiovascular implantable electronic device (CIED) implantation surgeries. Published guidelines on perioperative management of DM are reviewed.

RESULTS

We identified 30 studies reporting SSI and HbA1c values. The literature review indicated that for many surgical procedures, elevated HbA1c is not correlated to rate of SSI. We identified 16 studies reporting infection rates within DM cohorts following SCS, IDDS, and CIED implantation surgeries. The data reviewed did not indicate DM as an independent risk factor for SSI.

CONCLUSION

Preoperative HbA1c levels in patients with a history of DM is not a singularly sufficient tool to estimate risk of perioperative infection in SCS implantation surgery. Published guidelines on perioperative management of DM do not suggest a specific HbA1c above which surgery should be delayed; intentional perioperative glycemic control is recommended.

Effect of Acute Stress Glycemic Control and Long-Term Glycemic Control on the Incidence of Post-Operative Infection in Diabetics Undergoing Cardiac Surgery

Objective

Post-operative infection after cardiac surgery causes prolonged hospital stay and increased mortality. In patients with diabetes, peri-operative and pre-operative glycemic control have been associated with increased risk of post-operative infection. Saudi Arabia is the 7th highest country in the world for the prevalence of diabetes. In our surgical population the incidence of diabetes is 77%. We were aware of a high incidence of post-operative infections in our institution. The aim of this work was to assess how peri-operative and pre-operative glycemic control was related to the six-week incidence of post-operative infection.

Method

We retrospectively collected data for 174 adult patients with diabetes undergoing cardiac surgery between January 2017 and June 2019. For group analysis of peri-operative glycemic control, a mean value of ≤10 mmol/l was categorized as optimal control and a mean value of >10 mmol/l as sub-optimal control. The admission glucose value, the maximum glucose value and glycosylated hemoglobin A1c (HbA1c) were separately recorded. Admission HbA1c was used for optimal long-term control group (HbA1c ≤ 7%) and sub-optimal long-term control group (HbA1c > 7%).

Results

Of the 174 patients 60 (34%) developed infection in the six-week post-operative period. No statistically significant difference in infections was seen in the optimal peri-operative control group (n = 24, 14%) compared to sub-optimal peri-operative control group (n = 36, 21%; p = 0.113). However, patients with infection had a significantly higher mean glucose (10.4 mmol/l versus 9.9 mmol/l, p = 0.0316) than no infection.

Grouping according to their HbA1c: well controlled group (41, 24.0%) and poor control group (130, 76.0%) showed no difference in infections. However, patients with lower HbA1c had better glycemic control as measured by: initial glucose (r = 0.52, p=<0.001); mean peri-operative glucose (r = 0.45, p=<0.001); maximum recorded glucose (r = 0.41, p=<0.001).

Conclusion

The majority of our patients presented with sub-optimal long-term glycemic control which we linked to poor stress glycemic control perioperatively. Patients with post-operative infections had higher mean peri-operative blood glucose. With the high incidence of diabetes in Saudi Arabia we have demonstrated the importance of good pre-operative assessment which allows tighter peri-operative glycemic control to reduce post-operative morbidity.