dr-exmedic.com

One of the mantras I’ve heard, from my EMT class on, is that “too much oxygen never hurt anybody.”  It makes some sense at a gut level, and it’s resulted in the treatment of many, many patients with oxygen–far more than will ever be treated with it in the ED.  I know I’m not the only person who’s given oxygen to patients with abdominal pain, for example.

However, that’s one of the EMS truisms that needs to be erased from our collective memory.  While not proof of the concept that too much of anything can be bad for you, a new study in JAMA is certainly very suggestive.  I barely need to say very much if I just include the key table:

As you can see, among almost 3600 cardiac arrest victims, the mortality was lowest in the group with normal oxygen levels (45%), lower than both the hypoxic group (57%) and–more significantly–the hyperoxic group (63%), which actually had the highest mortality.  Even worse, the hyperoxic group was also less likely to be discharged home after surviving.

Now, the study itself was not structured to prove that too much oxygen is proven to harm:  it was just using observed data, not testing anything, so the best we can see is an association–not a cause.  However, it’s consistent with experimental data (mostly in pigs) suggesting that high levels of oxygen after ROSC can be harmful.

This is the sort of data that won’t change EMS practice overnight (unless you happen to already have a portable blood gas analyzer in the back of your ambulance–in which case, I’m extremely jealous).  However, it should help decrease our willingness to claim that “more is better.”