Authors: Elmer J et al. Intensive Care Med 2015 Jan.
Severe, but not moderate, hyperoxia portended lower survival to hospital discharge.
Hyperoxia may result in increased oxidative stress and ischemia-reperfusion injury in patients resuscitated from cardiac arrest. To assess the effect of hyperoxia on outcomes, investigators retrospectively analyzed data for 184 ventilated post–cardiac arrest patients (mean age, 60 years; 54% men) who survived at least 24 hours after resuscitation.
Severe hyperoxia was defined as PaO2 greater than 300 mm Hg; moderate or probable hyperoxia, PaO2 101–299 mm Hg; normoxia, PaO2 60–100 mm Hg; and hypoxia, PaO2 less than 60 mm Hg.
Overall, 46% of patients survived to hospital discharge. Of all patients, 36% had severe hyperoxia within the first 24 hours after arrest (mean duration, 1.4 hours). Severe hypoxia was associated with decreased survival to hospital discharge (adjusted odds ratio, 0.83 for each hour).
Conversely, moderate or probable hyperoxia was not associated with survival. Compared with severe hypoxia, moderate or probable hyperoxia was associated with improved organ function at 24 hours (unadjusted odds ratio, 0.94).
While moderate levels of hyperoxia may actually be beneficial, PaO2 values over 300 mm Hg are associated with worse outcomes. Oxygen is a drug and must be appropriately titrated for the best outcomes, just like other pharmacologic interventions. Although we should never withhold oxygen in a patient who needs it, high concentrations for long periods of time should be avoided.