Oxygen IS a drug, use it with caution, only when is needed.

This is a quick review on the potentially harmful effects of too much oxygen, published in this month's EPM magazine. 

THE POTENTIAL HARM OF OXYGEN THERAPY IN MEDICAL EMERGENCIES
Cornet, A.D., et al, Crit Care 17(2):313, April 18, 2013
These Dutch authors comment on possible harm from routine use of supplemental oxygen in patients with a medical emergency. Several early studies reported high-flow oxygen in myocardial infarction patients was associated with reduced cardiac output and stroke volume with an increase in systemic vascular resistance and arterial blood pressure, largely due to vasoconstriction, with no evidence of a benefit of hyperoxia on myocardial ischemia. Clinical trials of supplemental oxygen in patients with cardiac emergencies are limited, but a 2010 Cochrane review reported increased mortality in MI patients receiving supplemental oxygen (RR 3.0). Experimental evidence also suggests an adverse hemodynamic effect of oxygen in patients with congestive heart failure. The adverse effects of supplemental oxygen are more widely appreciated in patients with chronic obstructive pulmonary disease (COPD), and a recent randomized trial noted decreased mortality in COPD patients receiving titrated rather than high-concentration oxygen. 

Hyperoxia in stroke has been noted to be associated with a decrease in cerebral blood flow and increased mortality, and use of supplemental oxygen for most ischemic stroke patients is not supported in American Stroke Association guidelines. Several large studies reported increased mortality and poor neurologic outcomes in hyperoxic patients after resuscitation from cardiac arrest. Although it is possible that vasoconstriction due to hyperoxia might be beneficial in patients with shock, no studies have demonstrated a benefit of supranormal oxygen levels in this setting. The authors advise caution with the routine use of supplemental oxygen for medical emergencies. While hypoxemia should be treated promptly, they recommend slow stepwise titration and feel that an oxygen saturation of 90-94% may be reasonable. 61 references (cornet@vumc.nl – no reprints)

Conclusions:
- Oxygen IS toxic when used in high concentrations and for prolonged periods of time.
- Hyperoxia causes cellular dysfunction 
- Use it only when patient is hypoxic and when hypoxia has been corrected, titrate down to maintain normoxia.
- Share the knowledge and stop the ritual of putting every patient on oxygen !