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

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Should oxygen be given in myocardial infarction?

ResearchBlogging.org

In 2010, a Cochrane Review showed something that we already knew, but wanted to keep ignoring.

There is no evidence that supplemental oxygen improves outcomes for patients having an acute myocardial infarction, but there is evidence that oxygen is causing harm to these patients.

Should we continue to treat these patients with supplemental oxygen in the absence of either hypoxia or respiratory distress?

Dan Atar, professor and head of cardiology, wrote –

On the basis of physiological reasons and no trial evidence of harm: yes[1]

But is that a good enough reason to use supplemental oxygen for acute myocardial infarction outside of controlled trials?
 


Original cartoon
 

Consider these similar questions.

Should therapeutic phlebotomy (bleeding patients to remove bad humors) be used for myocardial infarction?

Up until there was clear evidence of harm from therapeutic phlebotomy, we could have given the same response – On the basis of physiological reasons and no trial evidence of harm: yes.

Our misunderstanding of physiology meant that we used to think that there was good physiologic support for bleeding patients. There was a lack of evidence of harm was only because we had neglected to study bleeding. Neglect is too mild a word for what we did to patients.

Is a possible physiological reason for something to work combined with a lack of evidence of harm (due to neglect) is a good enough reason to routinely use a treatment?

No.

That is a good enough reason to study the treatment, but it is not remotely a good enough reason to use the treatment like candy, or like spinal immobilization, or like oxygen. 😳

Is the lack of perfection in the research showing harm the same as evidence of safety?

Of course not, but that is what we are supposed to believe if we listen to alternative medicine practitioners.

Should rotating tourniquets be used for acute pulmonary edema?

How bad was our understanding of physiology?

How good was the evidence of harm?

Should antiarrhythmics be used for acute myocardial infarction?

How bad was our understanding of physiology?

How good was the evidence of harm?

The evidence of harm was good, but the evidence was taken from a different group of patients – those who had already has a myocardial infarction and were now having an arrhythmia that is consistent with a higher death rate. The research showed that we were getting rid of the arrhythmias very effectively, but we appear to have been killing thousands of patients by giving them the drugs.[2]

Being reasonable, a lot of doctors started backing off all use of antiarrhythmics. Getting rid of the rhythm is not the same as making the patient better.

What does this all mean for practising clinicians? To date, no contemporary high quality study has investigated inhaled oxygen as part of the treatment of myocardial infarction, and this should be remedied.[1]

Yes.

And while we are awaiting results, we should stop using supplemental oxygen in the absence of hypoxia or respiratory distress.

When there is evidence of harm, even bad evidence, we should be very cautious with the possible causes, until we have a better idea of whether there is actual harm, how much harm there is, and what is causing the harm.

Airlines and the air force will ground all planes of a particular type if there is a coincidence of crashes until they can explain what is going on.

In medicine, we make excuses for continuing to give these treatments and refusing to limit the treatments to controlled trials.

Pilots and passengers appear to be better protected than patients.

We worry about the influence of money on patient care decisions. Supplemental oxygen is one of the cheapest treatments we have and still doctors resist eliminating its use.

Money is not the biggest bias we have. Tradition is a big bias. The reluctance to admit that we have been harming patients may be an even bigger bias. Wishful thinking is probably the biggest bias.

We don’t want to harm our patients, but we refuse to acknowledge our biases. Our patients suffer for our hubris.

Can there be problems with cutting back on use, or eliminating use? Absolutely.

Droperidol (Inapsine) received a black box warning and is used much less frequently than it had been. Droperidol has been studied and found to be safer than amiodarone for QT segment prolongation leading to torsades, but few people use droperidol, while cardiac patients don’t seem to be able to get through a hospitalization without receiving amiodarone.[3]

Of course, the danger of cutting back on use, or eliminating use, assumes that there is some benefit from the treatment.

Droperidol has abundant evidence of benefit for excited delirium for nausea and vomiting, for management of many different types of pain.

Supplemental oxygen for acute myocardial infarction has no evidence of benefit, but there is evidence of harm.

How difficult is this question?

Is our priority our patients, or is our priority something else?

How much harm to patients is needed to be enough proof of harm?

Footnotes:

[1] Should oxygen be given in myocardial infarction?
Atar D.
BMJ. 2010 Jun 17;340:c3287. doi: 10.1136/bmj.c3287. No abstract available.
PMID: 20558515 [PubMed – indexed for MEDLINE]

[2] C A S T and Narrative Fallacy
Rogue Medic
Mon, 20 Jul 2009
Article

[3] Where are the Black Box Warnings on These Drugs – II
Rogue Medic
Sun, 11 Dec 2011
Article

Atar D (2010). Should oxygen be given in myocardial infarction? BMJ (Clinical research ed.), 340 PMID: 20558515

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  1. […] Sunday, I wrote about a doctor claiming that there is a screwy compelling idea that demonstrates that oxygen is good, regardless of the lack of evidence. He also claims that since there is not perfect proof that oxygen is harmful, that is PROOF that oxygen is good.   […]

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