Prognosis value of partial arterial oxygen pressure in patients with septic shock subjected to pre‐hospital invasive ventilation

Abstract

Objective: Mechanical ventilation can help improve the prognosis of septic shock. While adequate delivery of oxygen to the tissue is crucial, hyperoxemia may be deleterious. Invasive out‐of‐hospital ventilation is often promptly performed in life‐threatening emergencies. We propose to determine whether the arterial oxygen pressure (PaO2) at the intensive care unit (ICU) admission is associated with mortality in patients with septic shock subjected to pre‐hospital mechanical ventilation. Methods: We performed a monocentric retrospective observational study on 77 patients. PaO2 was measured at ICU admission. The primary outcome was mortality at day 28 (D28). Results: Forty‐nine (64%) patients were included. The mean PaO2 at ICU admission was 153 ± 77 and 202 ± 82 mm Hg for alive and deceased patients respectively. Mortality concerned 18% of patients for PaO2 < 100, 25% for 100 < PaO2 < 150 and 57% for a PaO2 > 150 mm Hg. PaO2 was significantly associated with mortality at D28 (p = 0.04). Using propensity score analysis including SOFA score, pre‐hospital duration, lactate, and prehospital fluid volume expansion, association with mortality at D28 only remained for PaO2 > 150 mm Hg (p = 0.02, OR [CI95] = 1.59 [1.20–2.10]). Conclusions: In this study, we report a significant association between hyperoxemia at ICU admission and mortality in patients with septic shock subjected to pre‐hospital invasive mechanical ventilation. The early adjustment of the PaO2 should be considered for these patients to avoid the toxic effects of hyperoxemia. However, blood gas analysis is hard to get in a prehospital setting. Consequently, alternative and feasible measures are needed, such as pulse oximetry, to improve the management of pre‐hospital invasive ventilation.