Characteristics and risk factors associated with mortality during the first cycle of prone secondary to ARDS due to SARS-CoV-2 pneumonia

Abstract

Objective: To analyze characteristics, changes in oxygenation, and pulmonary mechanics, in mechanically ventilated patients with ARDS due to SARS-CoV-2 treated with prone position and evaluate the response to this maneuver.

Design: Cohort study including patients with PaO₂/FiO₂ <150mmHg requiring prone position over 18 months. We classified patients according to PaO₂/FiO₂ changes from basal to 24h after the first prone cycle as: 1) no increase 2) increase <25%, 3) 25%-50% increase 4) increase >50%.

Setting: 33-bed medical-surgical Intensive Care Unit (ICU) in Argentina.

Patients: 273 patients.

Interventions: None.

Main variables of interest: Epidemiological characteristics, respiratory mechanics and oxygenation were compared between survivors and non-survivors. Independent factors associated with in-hospital mortality were identified.

Results: Baseline PaO₂/FiO₂ was 116 [97-135]mmHg (115 [94-136] in survivors vs. 117 [98-134] in non-survivors; p=0.50). After prone positioning, 22 patients (8%) had similar PaO₂/FiO₂ values; 46(16%) increased PaO₂/FiO₂ ≤25%; 55 (21%) increased it 25%-50%; and 150 (55%), >50%. Mortality was 86%, 87%, 72% and 50% respectively (p<0.001). Baseline PaO₂/FiO_2, <100mmHg did not imply that patients were refractory to prone position. Factors independently associated with mortality were age, percentage increase in PaO₂/FiO₂ after 24h being in prone, and number of prone cycles.

Conclusions: Older patients unable to improve PaO₂/FiO₂ after 24h in prone position and who require >1 cycle might early receive additional treatments for refractory hypoxemia. After the first 24h in the prone position, a low percentage of PaO₂/FiO₂ increase over baseline, beyond the initial value, was independently associated with higher mortality.

Keywords: ARDS; COVID; Decubitus prone; ECMO; Fallo prono; Hipoxemia refractaria; Posición prona; Prone failure; Prone position; Prono al decúbito; Refractory hypoxemia; SARS-CoV2; SDRA.