Systemic Oxygen Utilization in Severe COVID-19 Respiratory Failure: A Case Series.

Abstract

Management of hypoxemia in patients with severe COVID-19 respiratory failure is based on the guideline recommendations for specific SpO2 targets. However, limited data exist on systemic O2 utilization. The objective of this study was to examine systemic O2 utilization in a case series of patients with this disease. Between March 24, and April 9, 2020, 8 patients intubated for severe COVID-19 respiratory failure had near-simultaneous drawing of arterial blood gas (ABG), central venous blood gas (cVBG), and central venous oxygen saturation (ScvO2) at a mean of 6.1 days into hospitalization. Three patients were managed with indirect cardiac output (CO) monitoring by FloTrac sensor and Vigileo monitor (Edwards Lifesciences, Irvine, CA). The oxygen extraction index (OEI; SaO2-ScvO2/SaO2) and oxygen extraction fraction (OEF; CaO2-CvO2/CaO2 ≥ 100) were calculated. Values for hyperoxia (ScvO2 ≥ 90%), normoxia (ScvO2 71-89%), and hypoxia (ScvO2 ≤ 70%) were based on the literature. Mean values were calculated. The mean partial pressure of oxygen (PaO2) was 102 with a mean fraction of inspired O2 (FiO2) of 44%. One patient was hyperoxic with a reduced OEI (17%). Five patients were normoxic, but 2 had a reduced OEF (mean 15.9%). Two patients were hypoxic but had increased systemic O2 utilization based on OEF or OEI. In select patients with severe COVID-19 respiratory failure, O2 delivery (DO2) was found to exceed O2 utilization. SpO2 targets based on systemic O2 utilization may help in reducing oxygen toxicity, especially in the absence of anaerobic metabolism. Further data are needed on the prevalence of systemic O2 utilization in COVID-19. Garg RK, Kimbrough T, Lodhi W, DaSilva I. Systemic Oxygen Utilization in Severe COVID-19 Respiratory Failure: A Case Series. Indian J Crit Care Med 2021;25(2):215-218.