Without evidence of benefit, an intervention should not be presumed to be beneficial or safe.

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Evidence for Oxygen in Cardiac Arrest

Chris from EMS Patient Advocate One wrote 02 in cardiac arrest- curiosity to question me about a comment I made regarding Dr. Bryan Bledsoe’s algorithm prediction.

The future of ACLS. I’ll bet I’m much more right than wrong!

FaceBook page for original.

Where are the drugs?!?!?

All of the drugs that work are right there.

We just pretend that the drugs work, even though there is no evidence that they improve the important stuff – neurologically intact survival to discharge.

EMS Outside Agitator has a post, Is “Evidence based medicine” a sham, commenting on my post. I responded and included the following comment on that post.

“I disagree about the oxygen. Routine use of oxygen in resuscitation is not based on evidence, but treatment of hypoxia with oxygen is appropriate.”

. . . .

Right now my mind is telling me if someone goes down from a primary sudden cardiac cause, there is a good chance they are pre-oxygenated. When your heart and metabolism are not working, how much additional 02 do you need? Too much we know is bad right? Too little we know is bad.
Whatever happened to room air? That has about 21% 02 in it, way more than I pictured being used by the body in the state of cardiac arrest even with ROSC when giving BVM assistance

This is something that should be simple.

This is something that should have been studied enough to provide good answers long ago.

This is still not decided.

My comment is about the lack of evidence for routinely giving supplemental oxygen in cardiac arrest. We intubate, or use extraglottic airways, or BVMs (Bag Valve Mask resuscitators), but we have not even demonstrated that any ventilation is a good idea for the initial treatment of a cardiac arrest that does not appear to be due to a respiratory condition.

We routinely deliver high-flow oxygen in many places. Not for the patient, but to feel as if we are doing something and to perpetuate the oxygen is good and more is better mythology.

Oxygen can be bad. More can make things even worse. I will write about the non-arrest uses later, but last year there was a paper that dramatically changed the way many of us look at the use of oxygen in cardiac arrest.

This looks very bad for oxygen. The proportion of hyperoxic patients surviving is dramatically lower than the proportion of normoxic patients surviving.[1]

Disbelief in the results led another group to look at resuscitation data that controlled for illness severity.

This oxyhemoglobin dissociation curve (from The Michigan Nanotechnology Institute for Medicine and Biological Sciences) can be helpful in comparing the pulse oximetry numbers with the PO2/PaO2. For comparison, the green line running vertically through the image above is at about the same place as the green line running vertically through the image below.

The Better and Worse are the trends of the effects on outcome. This study also looks very bad for oxygen.[2]

But . . . –

When you adjust for severity of illness, their outcomes stop trending for the worse with hyperoxia (as measured in the ICU [Intensive Care Unit]).[2]

This is just a quick view of some charts, but it does suggest that oxygen is not the cause of the bad outcomes. We should probably wait for more data on this possible problem with hyperoxia. What we do need to focus on, oxygen-wise, is avoiding hypoxia. That does not mean that we should give high-flow oxygen to everyone dead, or near-dead, or recently dead.

Oxygen is still a drug. Oxygen does have indications. We should be able to assess the oxygenation of the patient and supplement oxygen only when it is indicated.

There are studies that show harm to living patients from supplemental oxygen, so we should not look at this study and decide to return to giving high-flow oxygen indiscriminately.

Oxygen is a good thing, when indicated and in the right dose, but that is probably not as much as possible.

Most cardiac arrest patients without signs of respiratory causes of cardiac arrest will probably be better off with just chest compressions. We can apply an oxygen mask to deliver passive oxygen insufflation and worry about the ventilation later. We still do not have evidence of better outcomes with ventilation during the initial minutes of resuscitation.

These patients probably do have enough oxygen in their blood for all of the metabolic needs of a recently dead, but not permanently dead, person.

Is the oxygen useless?

No. Hypoxia is common.

In each study there are many more patients in the hypoxia group than in the normoxia and hyperoxia groups combined.

Hypoxia does appear to produce significantly worse outcomes from cardiac arrest – even after adjusting for illness severity.


[1] Association between arterial hyperoxia following resuscitation from cardiac arrest and in-hospital mortality.
Kilgannon JH, Jones AE, Shapiro NI, Angelos MG, Milcarek B, Hunter K, Parrillo JE, Trzeciak S; Emergency Medicine Shock Research Network (EMShockNet) Investigators.
JAMA. 2010 Jun 2;303(21):2165-71.
PMID: 20516417 [PubMed – indexed for MEDLINE]

Free Full Text from JAMA with links to Free Full Text PDF Download

[2] Arterial hyperoxia and in-hospital mortality after resuscitation from cardiac arrest.
Bellomo R, Bailey M, Eastwood GM, Nichol A, Pilcher D, Hart GK, Reade MC, Egi M, Cooper DJ; the Study of Oxygen in Critical Care (SOCC) Group.
Crit Care. 2011;15(2):R90. Epub 2011 Mar 8.
PMID: 21385416 [PubMed – as supplied by publisher]

Free Full Text from BioMed Central Emergency Medicine with links to Free Full Text PDF Download



  1. Thank you for your answer and post! Always interesting-keep it coming.


  1. […] [12] Evidence for Oxygen in Cardiac Arrest Wed, 10 Aug 2011 Rogue Medic Article […]

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