Association between postoperative hyperglycemia and morbidity and mortality in older adults with and without diabetes undergoing myocardial revascularization and valve replacement surgeries

Abstract

Introduction: postoperative hyperglycemia, defined as blood glucose ≥140 mg/dL, is a common occurrence in cardiovascular surgeries and is associated with increased complications and mortality. In older adults, a particularly vulnerable population, this issue is of even greater relevance.

Objectives: to evaluate the association between blood glucose control during the first 24 postoperative hours and its impact on morbidity and mortality in patients over 65 years of age undergoing coronary artery bypass grafting and combined coronary artery bypass grafting with valve replacement. Additionally, to compare this association between patients with and without a prior diagnosis of diabetes mellitus.

Materials and methods: a prospective study was conducted between 2019 and 2024, including 310 patients over 65 years of age who underwent coronary artery bypass grafting or combined coronary artery bypass grafting with valve replacement. A continuous insulin infusion pump protocol was implemented and adapted to our population. Glycemic control was classified as "optimal" (mean glucose <180 mg/dL without hypoglycemia) or "non-optimal" (mean glucose ≥180 mg/dL), based on hourly glucose measurements during the first 24 hours after surgery. Postoperative complications during hospitalization and all-cause mortality were analyzed. Glycemic variability was assessed using the coefficient of variation, and multivariable logistic regression models were applied, adjusted for age, comorbidities, and other key factors.

Results: 37.5% of patients (n=115) had suboptimal glycemic control, and this group had a higher rate of complications compared with the group with optimal control (86.1% vs. 73.8%; p=0.012), including cerebrovascular accident (CVA) (3.5% versus 0%; p=0.009), acute kidney injury (ARF) (29.6% versus 18.3%; p=0.023), and all-cause mortality (10.4% versus 3.7%; p=0.017). There was no significant difference in the rate of surgical site infections in the suboptimal control group versus the optimal control group (4.3% versus 1%; p=0.061). In multivariate models, patients with a previous diagnosis of DM had a lower risk of complications (protective OR of 0.14; 95% CI: 0.02-0.8; p=0.024), while hyperglycemia ≥180 mg/dl was an independent risk factor for mortality (OR: 5.5; 95% CI: 1.7-17.6; p=0.004). Within this group, the relative risk of mortality was 2.29 (95% CI: 0.72-7.25) for the group of patients without a history of DM, however, a statistically significant difference was not reached (p = 0.181). CV was not significantly associated with mortality or with the combination of major complications in multivariate analyses (mortality: p=0.163; mortality + AMI and stroke: p=0.775).

Conclusions: non-optimal glycemic control (≥180 mg/dL) during the postoperative period in older adults undergoing coronary artery bypass grafting and valve replacement was an independent predictor of complications, including stroke, acute kidney injury, and all-cause mortality, with a greater impact observed in patients without a prior diagnosis of diabetes mellitus. These findings support the use of strict glucose monitoring protocols tailored to older adults.