The ΔPv-aCO2/ΔCa-vO2 ratio as a predictor of mortality in patients with severe acute respiratory distress syndrome related to COVID-19

Abstract

Objective To evaluate the central venous-to-arterial carbon dioxide difference combined with arterialto- venous oxygen content difference (ΔPv-aCO2/ΔCa-vO2 ratio) as a predictor of mortality in patients with COVID-19-related severe acute respiratory distress syndrome (ARDS). Methods Patients admitted to the intensive care unit with severe ARDS secondary to SARS-CoV-2, and invasive mechanical ventilation were included in this single-center and retrospective cohort study performed between April 18, 2020, and January 18, 2022. The tissue perfusion indexes (lactate, central venous oxygen saturation [ScvO2], and venous-to-arterial carbon dioxide pressure difference [ΔPv-aCO2]), anaerobic metabolism index (ΔPv-aCO2/ΔCavO2 ratio), and severity index (Simplified Acute Physiology Score II [SAPSII]) were evaluated to determine its association with the mortality through Cox regression analysis, Kaplan- Meier curve and receiver operating characteristic (ROC) curve. Results One hundred fifteen patients were included in the study and classified into two groups, the survivor group (n = 54) and the non-survivor group (n = 61). The lactate, ScvO2, ΔPv-aCO2, and ΔPv-aCO2/ΔCa-vO2 ratio medians were 1.6 mEq/L, 75%, 5 mmHg, and 1.56 mmHg/ mL, respectively. The ΔPv-aCO2/ΔCa-vO2 ratio (Hazard Ratio (HR) = 1.17, 95% confidence interval (CI) = 1.06-1.29, p = 0.001) was identified as a mortality biomarker for patients with COVID-19-related severe ARDS. The area under the curve for ΔPv-aCO2/ΔCa-vO2 ratio was 0.691 (95% CI 0.598-0.774, p = 0.0001). The best cut-off point for ΔPv-aCO2/ΔCa-vO2 ratio was >2.14 mmHg/mL, with a sensitivity of 49.18%, specificity of 85.19%, a positive likelihood of 3.32, and a negative likelihood of 0.6. The Kaplan-Meier curve showed that survival rates were significantly worse in patients with values greater than this cut-off point. Conclusions The ΔPv-aCO2/ΔCa-vO2 ratio could be used as a predictor of mortality in patients with severe ARDS secondary to SARS-CoV-2.