Poor Glycemic Control Predicts Higher Mortality in Critically Ill Patients with COVID-19 and Hyperglycemia

Purpose: Hyperglycemia frequently occurs in critically ill patients with COVID-19 and may worsen outcomes. This study evaluated the prevalence, predictors, and clinical impact of poor glycemic control in severe and critical cases. Methods: We conducted a retrospective observational study of 338 ICU patients with COVID-19 and hyperglycemia at a tertiary center in Vietnam (August 2021–February 2022). Nearly 15,000 bedside glucose measurements were analyzed. Patients were classified into well-controlled or poorly controlled groups based on mean glucose levels (140–180 mg.dL−1 target). Logistic regression identified predictors of poor control. The primary outcome was in-hospital mortality. Propensity score matching (PSM) and multivariable Cox regression were performed to adjust for confounders. Results: Poor glycemic control occurred in 79% of patients. Independent predictors included invasive mechanical ventilation, elevated admission glucose, pre-existing diabetes, HbA1c > 7.0%, and prolonged corticosteroid exposure. After PSM, mortality was higher in the poorly controlled group compared to the well-controlled group (54.8% vs. 35.5%, p = 0.047). Cox regression confirmed poor glycemic control as an independent predictor of death (adjusted hazard ratio [HR] 1.61, 95% confidence interval [CI] 1.01–2.55, p = 0.045). Conclusions: Poor glycemic control is common and strongly associated with excess mortality in critically ill COVID-19 patients. Prolonged corticosteroid use emerged as a modifiable risk factor. Careful glucose monitoring and tailored steroid management are warranted to improve outcomes.