Introduction: There are limited studies examining the association between diabetes and postoperative outcomes outside of the cardiac surgery setting. Our objective was to investigate the independent association of diabetes defined categorically or using HbA1c as a continuous variable, with outcomes following surgery.
Methods: In this prospective, observational cohort study, all patients ≥54 years admitted to Austin Health between July 2013 to February 2016 had an automated HbA1c measurement as part of the Diabetes Discovery Initiative. Patients were diagnosed with diabetes if they had an HbA1c≥6.5% or a pre-existing diagnosis of diabetes, and prediabetes if they had an HbA1c of 5.7-6.4%. Baseline demographic and clinical data were obtained from hospital records and patients were followed up for 6 months. Random-effect logistic and negative binomial regression models were used for analysis, with surgical units treated as random effects.
Results: 7565 hospital admissions of patients undergoing surgery were studied, with 30% of patients having diabetes and 37% having prediabetes. After adjustment for age, Charlson comorbidity index excluding diabetes, estimated glomerular filtration rate, and length of surgery, diabetes, defined categorically, was associated with increased hospital length of stay (IRR=1.09; 95%CI: 1.05-1.14; p<0.001), 6-month mortality (OR=1.29; 95%CI: 1.05-1.58; p=0.015), intensive care unit (ICU) admission (OR=1.54; 95%CI: 1.32-1.79; p<0.001), mechanical ventilation (OR=1.69; 95%CI:1.35-2.13; p<0.001), and major complications as defined by Clavien-Dindo grade ≥4 (OR=1.38; 95%CI:1.18-1.58; p<0.001) (Table 1). Furthermore, each percentage increase in HbA1c was associated with increased hospital length of stay (IRR=1.05; 95%CI:1.03-1.07; p<0.001), ICU admission (OR=1.14; 95%CI: 1.07-1.21; p<0.001), and major complications (OR=1.08; 95%CI:1.01-1.14; p=0.019) (Table 1). No significant association between prediabetes, defined categorically, and adverse outcomes was observed.
Conclusion: Diabetes and higher HbA1c were independently associated with higher risk of adverse outcomes following surgery. Studies are necessary to examine the role of intensive pre- and postoperative glycaemia management of patients with diabetes.