Oxygen in MI

 

Oxygen%20(Custom)%20(2)

My initial training as a Paramedic (and I’m sure this reflected by most others) was that in the setting of any suspected ischaemic cause to chest pain(and especially in a confirmed STEMI) high follow oxygen should be placed immediately onto the patient. Non rebreathers were standard care for MI.  The biological plausibility model went along the lines of increasing the partial pressure of O2 in the alveoli would therefore super saturate the plasma, even though the SPO2 was already almost 100%.  Reduced bloodflow through stenotic coronary arteries would have the maximum amount of O2 to deliver to ischaemic myocardial tissue.

Certainly sounded plausible to me at the time.

oxygen-heart-attack

However in recent years there has been a lot of talk about potential harm of oxygen in these patients.  So let’s review the evidence.

A few years ago the Cochrane Collaboration published a systematic review on Oxygen and AMI, available below:

20556775_ Oxygen therapy for acute myocardial infarction

The accumulated numbers from three included trials were not seen to gain full statistical significance, however potential harm was a derived assumption, and no benefit was seen from O2 administration.

These trials involved a total of 387 patients of whom 14 died. Of those who died, nearly three times as many people known to have been given oxygen died compared to those known to have been given air.

A short summary of the review at this link:

http://lifeinthefastlane.com/oxygen-in-acute-myocardial-infarction/

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http://www.scancrit.com/2014/11/26/avoid-oxygen/#more-7811

AVOID study recently conducted by Ambulance Victoria found a 5 fold increase in MI damage from O2 administration over air. 8LPM was used vs air.

Here’s the actual published study:

26002889_ Air Versus Oxygen in ST-Segment Elevation Myocardial Infarctionamerican-heart-avoid-study-air-versus-oxygen-in-stelevation-myocardial-infarction-1-638

441 patients were considered for endpoint analysis.  The Swedish study mentioned on the scancrit post is deto2x, a Swedish RCT aiming to recruit 6600 normoxic patients with AMI to 6lpm or air.  The results of this will be very interesting!

Here’s the pilot study and the trial design:

24576515_ DETermination of the role of OXygen in suspected Acute Myocardial Infarction trial

For comparison to our very basic protocols on this matter check out QAS and AV Oxygen guidelines:

http://www.ambulance.vic.gov.au/media/docs/Adult%20CPG%20wm-a01f0e1e-4fc0-405c-bc83-3136adf4a723-0.pdf
AV956469-mud-arrest

https://ambulance.qld.gov.au/docs/clinical/dtprotocols/DTP_Oxygen.pdf

QAS Drug Therapy Guideline for Oxygen:  very comprehensive guide to treatment.

With the evidence accumulating against using O2 in AMI, how do we go about changing our ‘dogma’ and improving our practise for the good of patients?

The following cross sectional study of UK health providers found 98.3%(n=524) routinely or always use oxygen for AMI or ACS, and only 1.3% believed there was any association of it’s use and increased mortality.

20385680_ Oxygen use in acute myocardial infarction_ an online survey of health professionals’ practice and beliefs

Cliff Reid on Dogmalysis(20:35 for Oxygen in chest pain topic):

Take home message: Normoxaemic ACS or AMI patients do not require oxygenation.

Keep an eye out for results from future RCT’s for more evidence on this.

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One Response to Oxygen in MI

  1. Damian Hughes says:

    Fortunately the oxygen protocol is about to change to reflect the need to be more judicious with its use. It possibly doesn’t go far enough but its a start.

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