Impact of decreased levels of total CO2 on in-hospital mortality in patients with COVID-19

Decreased total CO(2) (tCO(2)) is significantly associated with all-cause mortality in critically ill patients. Because of a lack of data to evaluate the impact of tCO(2) in patients with COVID-19, we assessed the impact of tCO(2) on all-cause mortality in this study. We retrospectively reviewed the data of hospitalized patients with COVID-19 in two Korean referral hospitals between February 2020 and September 2021. The primary outcome was in-hospital mortality. We assessed the impact of tCO(2) as a continuous variable on mortality using the Cox-proportional hazard model. In addition, we evaluated the relative factors associated with tCO(2) ≤ 22 mmol/L using logistic regression analysis. In 4,423 patients included, the mean tCO(2) was 24.8 ± 3.0 mmol/L, and 17.9% of patients with tCO(2) ≤ 22 mmol/L. An increase in mmol/L of tCO(2) decreased the risk of all-cause mortality by 4.8% after adjustment for age, sex, comorbidities, and laboratory values. Based on 22 mmol/L of tCO(2), the risk of mortality was 1.7 times higher than that in patients with lower tCO(2). This result was maintained in the analysis using a cutoff value of tCO(2) 24 mmol/L. Higher white blood cell count; lower hemoglobin, serum calcium, and eGFR; and higher uric acid, and aspartate aminotransferase were significantly associated with a tCO(2) value ≤ 22 mmol/L. Decreased tCO(2) significantly increased the risk of all-cause mortality in patients with COVID-19. Monitoring of tCO(2) could be a good indicator to predict prognosis and it needs to be appropriately managed in patients with specific conditions.