Excess oxygen administration and adverse outcomes in patients with SARS-CoV-2 pneumonia requiring invasive mechanical ventilation: a retrospective study

ABSTRACT

Introduction: Even if life-saving in most cases, excess O2 may have adverse effects. We described the prevalence of hyperoxemia and excess O2 administration in patients with severe acute respiratory syndrome due to novel coronavirus (SARS-CoV-2) and explored the association with mortality in the intensive care unit (ICU) or ventilatorassociated pneumonia (VAP). Methods: Retrospective single-centre study on 134 patients with SARS-CoV-2 requiring mechanical ventilation for ≥ 48 h. We calculated the excess O2 administered based on an ideal arterial O2 tension ( PaO2) target of 55-80 mmHg. We defined hyperoxemia as PaO2 > 100 mmHg and hyperoxia + hyperoxemia as an inspired O2 fraction (FiO2) > 60% + PaO2 > 100 mmHg. Risk factors for ICU-mortality and VAP were assessed with multivariate analyses. Results: Each patient received an excess O2 of 1121 [829-1449] l per day of mechanical ventilation. Hyperoxemia was found in 38 [27-55] % of arterial blood gases, hyperoxia + hyperoxemia in 11 [5-18] %. The FiO2 was not reduced in 69 [62-76] % of cases of hyperoxemia. Adjustments were more frequent with higher PaO2 or initial FiO2 levels. ICU-mortality was 32%. VAP was diagnosed in 48.5% of patients. Hyperoxemia (odds ratio [OR] 1.300 95% confidence interval [1.097- 1.542]) and hyperoxia + hyperoxemia (OR 1.144 [1.008-1.298]) were associated with higher risk for ICU-mortality, independently of age, Sequential Organ failure Assessment score at ICU-admission and mean PaO2/FiO2. Hyperoxemia (OR 1.033 [1.006-1.061]), hyperoxia + hyperoxemia (OR 1.038 [1.003-1.075]) and daily excess O2 (OR 1.001 [1.000- 1.001]) were identified as risk factors for VAP, independently of body mass index, blood transfusions, days of neuromuscular blocking agents before VAP, prolonged prone positioning and mean PaO2/FiO2 before VAP. Conclusions: Excess O2 administration and hyperoxemia were common in mechanically ventilated patients with SARS-CoV-2 and may be associated with ICU-mortality and greater risk for VAP.