Increased glycemic variability in patients with elevated preoperative HbA1C predicts adverse outcomes following coronary artery bypass grafting surgery.
BACKGROUND
In the setting of protocolized glycemic control, the relationship between postoperative glycemic variability on major adverse events (MAEs) after cardiac surgery is unknown for patients with increased preoperative hemoglobin A1C (HbA1C >6.5%). In this study, we sought to establish (a) whether postoperative glycemic variability is associated with MAEs after CABG surgery and (b) whether preoperative HbA1C could identify patients at increased risk of postoperative glycemic variability.


METHODS
Patients undergoing coronary artery bypass grafting with or without valvular surgery from January 2008 to May 2011 were enrolled in this prospective, single-center, observational cohort study. Demographic, intraoperative, and postoperative outcome data were obtained from institutional data collected for the Society of Thoracic Surgery (STS) database. The primary outcome, MAE was a composite of in-hospital death, myocardial infarction (MI), reoperations, sternal infection, cardiac tamponade, pneumonia, stroke, or renal failure. Glycemic variability in the postoperative period was assessed by the coefficient of variation (CV). CV was used as quartiles for the multivariate logistic regression. Variable selection in multivariable modeling was based on clinical and statistical significance and was performed in a hierarchical fashion.


RESULTS
Of the 1461 patients enrolled, 9.8% had an MAE. Based on the established target of HbA1C <6.5% for the diagnosis of diabetes mellitus, we considered HbA1C as a binary variable (<6.5% and ≥6.5%) in our primary analysis. Multivariate logistic regression analyses for the preoperative variables only revealed that preoperative HbA1C (odds ratio [OR], 1.6; 95% confidence interval [CI], 1.1-2.3; P = 0.02), history of MI (OR, 1.9; 95% CI, 1.3-2.8; P = 0.001), and STS risk score per quartile (OR, 1.7; 95% CI, 1.4-2.1; P < 0.001) were associated with MAEs. When postoperative variables were included in the analyses, postoperative glycemic variability (CV per quartile) in the intensive care unit (OR, 1.3; 95% CI, 1.1-1.5; P = 0.03), mean glucose levels averaged over the first 4 postoperative hours (OR, 1.2; 95% CI, 1.0-1.4; P = 0.03), history of MI (OR, 1.8; 95% CI, 1.2-2.6; P = 0.004), and STS risk score per quartile (OR, 1.6; 95% CI, 1.3-2.0; P < 0.001) were associated with MAEs. Glycemic variability as assessed by CV was increased postoperatively in patients with preoperative HbA1C ≥6.5% (0.20 ± 0.09 vs 0.16 ± 0.07, P < 0.001).


CONCLUSIONS
Postoperative glycemic variability is associated with MAEs after cardiac surgery. Glycemic variability is only measured when the patient leaves the intensive care unit, and there is no opportunity to intervene earlier. Preoperative HbA1C identifies risk for postoperative glycemic variability and may provide a more rational guide for targeting measures to reduce variability.
From the Department of Anesthesiology, Critical Care and Pain Medicine, Beth Israel Deaconess Medical Center, Boston, Massachusetts; Clinical Research Center, Soroka University Hospital and Faculty of Health Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel; and Departments of Anesthesiology and Surgery, Beth Israel Deaconess Medical Center, Boston, Massachusetts. Victor Novack, MD, PhD, is currently with Faculty of Health Science, Soroka University Medical Center, Ben-Gurion University, Beer-Sheva, Israel.
Balachundhar
B
Subramaniam
Adam
A
Lerner
Victor
V
Novack
Kamal
K
Khabbaz
Maya
M
Paryente-Wiesmann
Philip
P
Hess
Daniel
D
Talmor
D000368:Aged; D001786:Blood Glucose / Q000032:analysis* / Q000378:metabolism; D001026:Coronary Artery Bypass / Q000009:adverse effects* / Q000379:methods*; D003324:Coronary Artery Disease / Q000097:blood / Q000601:surgery; D005260:Female; D006442:Glycated Hemoglobin / Q000737:chemistry*; D006801:Humans; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D009203:Myocardial Infarction / Q000175:diagnosis; D016017:Odds Ratio; D011184:Postoperative Period; D011446:Prospective Studies; D012086:Reoperation; D012307:Risk Factors; D016896:Treatment Outcome; D014946:Wound Infection / Q000175:diagnosis
D001786:Blood Glucose; D006442:Glycated Hemoglobin