乌鸦传媒

BARCELONA -- Routine supplemental oxygen for suspected myocardial infarction patients without hypoxemia might be common, but it doesn't help outcomes, the DETO2X-AMI randomized registry trial affirmed.

All-cause mortality at 1 year after randomization occurred in 5.0% of patients initially given oxygen and 5.1% given room air only (HR 0.97, 95% CI 0.79-1.21), reported Robin Hofmann, MD, of the Karolinska Institutet in Stockholm, at the meeting and online in the New England Journal of Medicine.

Rehospitalization with MI within 1 year occurred in 3.8% given oxygen and 3.3% given ambient air (HR 1.13, 95% CI 0.88-1.46). More immediate measures, too, showed no difference between groups:

• Extent of myocardial injury as measured by high-sensitivity cardiac troponin T during hospitalization in those with confirmed MI
• 30-day death, rehospitalization with MI, or the composite

The findings with oxygen through an open face mask given at 6 L/min for 6 to 12 hours in the trial were consistent across subgroups, whether by baseline characteristics or final diagnosis.

But while the results were neutral, they did not confirm the larger infarct size and trend for higher mortality seen with supplemental oxygen given at 8 L/min through a closed mask to non-hypoxic ST-segment elevation MI patients in the AVOID trial.

While the design of the two trials differed in various ways, the bottom line message was similar that there was clearly no benefit, wrote Joseph Loscalzo, MD, PhD, of Brigham and Women's Hospital in Boston, in an accompanying editorial.

"Although the mechanisms underlying physiological and biochemical adaptation to myocardial ischemia are complex, the answer to the question is straightforward, and its implications for coronary care are indisputable: supplemental oxygen provides no benefit to patients with acute coronary syndromes who do not have hypoxemia," he wrote. "It is clearly time for clinical practice to change to reflect this definitive evidence."

“At the moment, doctors don’t actively discourage it,” commented Stephan Achenbach, MD, University of Erlangen, Germany, who noted that his center still does it.

Fred Masoudi, MD, of the University of Colorado Hospital in Aurora, went one step further:

“In my practice at least, I know when I go down to the emergency room, if I see a patient with a suspected myocardial infarction and see that they have no supplemental oxygen provided to them it feels almost as if they’re not wearing a hospital gown, like somehow they’re naked and they really should be wearing these oxygen prongs.”

But that should change, Hofmann told 乌鸦传媒 at the press conference.

“There are two things you will win: One is time. It takes time to supply oxygen, and this time we can use for things that actually are good for patients. The other thing is oxygen is not expensive, but it’s not for free. In the U.S. there was a calculation of about $100 per patient per day and now we’re speaking of thousands, of millions of patients with suspected myocardial infarctions in the world.”

He also acknowledged physicians’ and patients’ expectation that oxygen should be part of standard treatment. “This was the most common reason in our trial to not participate,” he said.

Hofmann also noted that dropouts in the oxygen group were driven simply by patients’ not wanting it. “So I don’t think in practice this is a big problem to not use it as much anymore.”

give oxygen therapy a class I recommendation, albeit with evidence level C, in this setting for hypoxic patients with arterial oxygen saturation of less than 90%. But the ESC specifies that routine oxygen is not recommended when oxygen saturation is at least 90%. Patients with oxygen saturation below that level were excluded from the DETO2X-AMI trial.

The say supplemental oxygen should be administered when arterial oxygen saturation is less than 90% or patients have respiratory distress or other high-risk features of hypoxemia. This recommendation (again with evidence level C) noted potential risks seen in AVOID but didn’t specifically recommend against use in patients who are not hypoxic.

DETO2X-AMI was needed because recommendations for non-hypoxic patients were not based on randomized trials, Richard Chazal, MD, of Lee Memorial Health System in Fort Myers, Fla., and immediate past president of the ACC, told Medpage Today.

The pragmatic, open-label trial included 6,629 patients from the SWEDEHEART nationwide Swedish registries for patient enrollment and data collection.

At the end of a median 11.6 hours of oxygen therapy, median oxygen saturation was 99% in those randomized to it, compared with 97% among patients randomized to ambient air only. Hypoxemia was less common with oxygen administration, as expected (1.9% vs 7.7%).

Study limitations included the open-label design due to lack of pressurized air in Swedish ambulances and concern that "available closed Hudson masks might have put patients at risk for carbon dioxide retention if they had been used as a sham comparator." Also, the endpoints were not centrally adjudicated, although that's not a concern for mortality, the researchers noted.

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