A new study led by a Vancouver-based doctor could change the way heart attack patients are treated around the world.
The research says a common practice dating back 50 years may be doing more harm than good.
Oxygen has been a first line treatment for heart attacks, even though there was no proof it actually helped.
“The concerning thing was as far back as 40 or 50 years ago, there were the beginnings of evidence to suggest the oxygen in high levels may be toxic for the heart,” says Dr. Dion Stub, cardiologist at St. Paul’s Hospital.
In recent years, concern has grown over the practice.
Dr. Stub, an Australian cardiologist who has been training at St. Paul’s, launched a study with a trial in Melbourne, Australia.
When the paramedics would arrive on scene, they would open an “randomization envelope.” Based on what was inside the envelope, they would give half of the patients high-flow oxygen by mask, and the other half no mask and no oxygen
441 heart attack patients were involved in the study which was recently published.
“We found in that in the group given oxygen, we found a 25% increase in blood test of heart injury of myocardial impact size in those we gave oxygen compared to no oxygen,” says Stub.
Not only did those who were given oxygen occur more heart damage, they developed more dangerous heart rhythms and more repeat heart attacks
The reason? Too much oxygen can be toxic.
“There have been some studies that show that very high levels of oxygen in blood can reduce coronary artery blood flow to heart and clamp arteries down so they constrict,” says Stub.
The problem was that 94% of the heart attack patents didn’t need more oxygen. Their blood oxygen levels were actually good.
“Certainly in the pre-hospital setting, all patients should have a pulse oximeter — very simple to measure oxygen in blood and should that be normal. We would caution against giving oxygen,” says Stub.
He says more studies are required before sweeping changes to guidelines can be made.
Even so, a growing number of countries are already checking heart attack patients’ levels before administering oxygen.
— with files from Linda Aylesworth, Global News