The role of serum lactate and hypotension in mortality risk stratification for critically ill COVID-19 patients: insights from a large retrospective ICU cohort.

PURPOSE: To determine the association of serum lactate levels with ICU outcomes in COVID-19 patients, particularly concerning hypotension, shock, and mortality. METHODS: Retrospective single center cohort study conducted in the intensive care unit. Adult patients (≥ 18 years) pneumonia admitted to the ICU with confirmed COVID-19 between March 2020 and December 2021. Patients were categorized into four lactate level categories: Very Low (< 1.7 mmol/L), Low (1.7-2.1 mmol/L), Intermediate (2.1-2.7 mmol/L), and High (> 2.7 mmol/L). Univariate and multivariate stepwise logistic regression analyses were conducted to identify independent predictors of all-cause mortality. The primary outcome was in-hospital mortality. RESULTS: Among the 1,371 patients studied, in-hospital mortality rates increased progressively across lactate categories, with 23% in the Very Low category, 31% in the Low category, 38% in the Intermediate category, and 51% in the High category (p < 0.001). Relative risk of in-hospital mortality was 1.37 (95% CI 0.99-1.89; p = 0.14) for the Low category, 1.66 (95% CI 1.23-2.23; p = 0.018) for the Intermediate category, and 2.24 (95% CI 1.69-2.97; p < 0.001) for the High category, compared to Very Low category. After regrouping the "Very Low" and "Low" categories as "Lower" (n = 446) and the "Intermediate" and "High" categories as "Higher" (n = 925), the mortality rate was 22.8% in the "Lower" category and 77.2% in the "Higher" category (RR 1.63 CI 95% 1.38-1.92) (Pearson Chi-Square, p < 0.001). The presence of hypotension significantly increased the risk of death across all categories, with relative risks ranging from 4.38 to 5.81. CONCLUSION: Elevated lactate levels are associated with increased mortality, and hypotension significantly exacerbates this risk across all lactate categories, highlighting its strong predictive power for adverse outcomes in this patient population.