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.