Cochrane: Benefits of oxygen therapy during MI unclear

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During a heart attack, patients are commonly administered oxygen to improve the oxygenation of the heart tissue; however, a meta-analysis of pooled data showed  that oxygen may actually add to a patient’s risk of dying, but the results still remain unclear, according to the latest issue of the Cochrane Systematic Review.

“Oxygen (O2) is widely recommended for patients with myocardial infarction yet a narrative review has suggested it may do more harm than good," the authors wrote. “Systematic reviews have concluded that there was insufficient evidence to know whether oxygen reduced, increased or had no effect on the heart ischemia or infarct size.”

To examine this further, Juan B. Cabello, MD, of the Hospital General Universitario de Alicante in Alicante, Spain, and colleagues looked at MI data from prior randomized controlled trials including the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, LILACS, PASCAL and others.

After combing data, the researchers identified three studies that met the inclusion criteria and were used for evaluation during the analysis.

“There is little evidence that this intervention improves outcomes for heart patients and some evidence even suggests it may cause further damage,” the authors wrote.

The authors identified 387 patients who had suspected or proven acute MI (AMI) to participate in the study and oxygen or air was given to the patients to inhale 24 hours after the onset of heart attack symptoms occurred. During the study, the researchers measured primary endpoints including death, pain and adverse events.

According to the authors, the intervention was inhaled oxygen given by a device at normal pressure for an hour or more anytime within the first 24 hours of the onset of AMI symptoms. The authors excluded hyperbaric oxygen or aqueous oxygen therapy.

During the study, 14 patients of the 387 died during the trial and the amount of patients who inhaled oxygen opposed to air was three-fold.

This result does not necessarily mean that giving oxygen increases the risk of dying from a heart attack,” said author of the study Amanda Burls of the University of Oxford in Oxford, England. "The numbers are so small that this may just have been due to chance."

Additionally, the authors wrote, “In both the intention-to treat meta-analysis and the confirmed AMI meta-analysis, there were more deaths among those patients on oxygen than for patients on air, although this did not reach statistical significance and could simply be a chance occurrence.”

The results also showed that the relative risk of death was 2.88 with intention-to-treat analysis and 3.03 for patients with confirmed AMI.

Further research must be conducted in order to obtain solid evidence that employing oxygen does not cause MI patients harm, they wrote.

“The evidence in this area is sparse, of poor quality and pre-dates the advances in reperfusion techniques and trial methods,” the authors concluded. “Current evidence neither supports nor clearly refutes the routine use of oxygen in patients with AMI.”