Abstract 275: Oxygen Weaning is Slow and Highly Variable Among Mechanically Ventilated Patients After Out-Of-Hospital Cardiac Arrest

Abstract

Introduction: Arterial hyperoxia at 6 h following resuscitation from out-of-hospital cardiac arrest (OHCA) may be associated with worsened survival and neurologic outcome. While global resuscitation guidelines call for prompt weaning of inhaled oxygen fraction (FiO2) following return of spontaneous circulation, with titration to oxygen saturation (SaO2) >92%, the burden of hyperoxia (both FiO2 and duration) among OHCA patients in the emergency department (ED) and critical care setting is unknown. Objectives: We sought to characterize oxygen weaning behavior in a cohort of resuscitated and mechanically ventilated OHCA patients from two hospitals, with “hyperoxic exposure burden” defined as cumulative treatment hours with FiO2>0.6. We hypothesized that the majority of these patients receive at least 6 h of hyperoxic exposure despite concomitant SaO2>92% during and after weaning. Methods: A retrospective study of post-arrest care was performed at two academic hospitals from 1/2018-12/2018; both hospitals have well-developed post-arrest care protocols that include oxygen weaning instructions. Consecutive non-traumatic, adult (age>17 y) OHCA patients treated in the emergency department that achieved sustained ROSC and received mechanical ventilation were included. Demographic data, as well as data on FiO2, SaO2 and arterial blood gas results, were collected for the first 24 h of post-arrest care. Results: 70 adult OHCA patients were included. Mean age was 61 y (SD 16.4), 51% were male, and 20% had initial shockable arrest rhythms. Survival to discharge was 21%. Median ED patient care time before ICU transfer was 2.7 h (IQR: 1.9-4.0). FiO2>=0.6 was administered to 52% of the cohort for at least 6 h; the median duration of hyperoxic exposure burden was 8.7 h (IQR: 3.9-15.0) with a wide range from 0.6-92 h. Among all patients with 6 h or more with FiO2>=0.6, median partial pressure of arterial oxygen was 136 mm Hg (IQR: 94-301) as measured during this period. Conclusions: Most resuscitated OHCA patients received substantial exposure to hyperoxia, and the timing of oxygen weaning was highly variable. Additional clinical investigation is required to understand the barriers to rapid weaning and to test the effect of improved weaning on clinical outcomes.