PaO2 and PaO2/FiO2 are prognostic indicators for patients treated by Extra Corporeal Life Support after Out Hospital Cardiac Arrest 


R. Jouffroy1, B. Vivien1, P. Philippe1, T. Maraffi1 and P. Carli1

1 Intensive Care Unit, Anaesthesiology department and SAMU of Paris, Hôpital Necker, Assistance Publique Hôpitaux de Paris, Paris Descartes University, Paris, France

Abstract: 
Objective: To examine whether values of PaO2 or PaO2/FiO2 (P/F) taken immediately (H0), at 3hours (H3) and 6 hours (H6) after starting Extra Corporeal Life Support (ECLS) inserted in a general intensive care unit indicate prognosis in patients treated by ECLS after Out Hospital Cardiac Arrest. 
Design: Retrospective observational study.
Setting: University teaching hospital general adult intensive care unit.
Patients: 20 consecutive patients admitted to the intensive care unit after refractory Out Hospital Cardiac Arrest treated by Extra Corporeal Life Support.
Interventions: Arterial blood samples were obtained on admission and every 3hours after starting ECLS into the intensive care unit. 
Measurements and results: PaO2 and P/F concentrations were measured from the blood samples. Both PaO2 and P/F samples on admission have good prognostic abilities at H0 (area under the curve on receiver operating characteristic analysis of 0.89, 0.68 respectively) and at H3 (area under the curve on receiver operating characteristic analysis of 0.80, 0.72 respectively) and moderate abilities at H6 (area under the curve on receiver operating characteristic analysis of 0.44, 0.65 respectively). The value of the PaO2 at H0, H3 and H6 after starting ECLS with the best predictive ability was a PaO2 greater than 200mmHg and the corresponding value for P/F greater than 240. 
Conclusions: PaO2 and PaO2/FiO2, measured at H0, H3 and H6 after starting ECLS for refractory OHCA can be used to predict outcome. PaO2 is more sensitive and more specific than PaO2/FiO2 at H0 and H3 to identify patients who have a high risk for mortality. These variables underline the potential toxicity of high dose of oxygen. A max value of PaO2 greater than 200mmHg during the first 6 hours seems to be a target during treatment of OHCA treated by ECLS.

PaO2 and PaO2/FiO2 are prognostic indicators for patients treated by extra corporeal life support after out hospital cardiac arrest