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

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?2?2?>?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.