NEW YORK - Dutch researchers say their meta-analysis found no support for routinely giving critically ill patients high-dose oxygen, a common practice among paramedics and emergency physicians.
"There is not a single study that points to beneficial effects," said Dr Yvo Smulders from VU University Medical Centre in Amsterdam. "All of the evidence that we found points to detrimental effects."
But many guidelines recommend oxygen in emergency settings, he and his colleagues noted in their report, published online in Archives of Internal Medicine.
"What you would expect is that oxygen is healthy," Dr Smulders told Reuters Health. "But it seems that God didn't introduce 20% oxygen in room air for nothing."
Many stroke patients dead from extra oxygen
Dr Smulders' team gathered all the human research they could find on supplemental oxygen after heart attacks, strokes, cardiac arrest and acute attacks of chronic obstructive pulmonary disease.
The 18 studies they came up with all had the same grim message: supplemental oxygen doesn't work, and there is some weak evidence that it might be harmful.
For instance, one trial from 1976 found nine out of 80 heart attack patients who got oxygen died, compared to just 3 out of 77 who got compressed air. Although that difference wasn't statistically significant, it was still bad news for oxygen.
Another trial, this one in stroke patients, had to be stopped early because too many patients who got extra oxygen died.
Monitor blood levels of oxygen
And for cardiac arrest, researchers reported last year that people with a lot of oxygen in their blood after they were revived died more often than people with normal levels.
"It has potentially far-reaching implications, because supplemental oxygen is just ubiquitous in the care of critically ill patients," Dr Stephen Trzeciak from Cooper University Hospital in Camden, New Jersey, who led that work, told Reuters Health.
On the other hand, he warned, so far there is no iron-clad proof that supplemental oxygen is harmful, whereas it's clear that too little oxygen can be lethal.
The American Heart Association currently recommends that after the initial emergency is past, doctors and paramedics monitor blood levels of oxygen to ensure they don't get too high. But what often happens is that providers just leave the oxygen on full blast, according to Dr Michael Sayre of the American Heart Association.
Give oxygen to patients with hypoxemia
"They don't realise they are giving too much oxygen," Dr Sayre told Reuters Health. "It's just not something they are paying attention to."
The Dutch researchers call for more studies. But until then, Dr Smulders said, health providers should only give oxygen to patients with hypoxemia.
"I think it is about time that you step away from your intuitive approach and look at the evidence," he said.
By Frederik Joelving
(Reuters Health, January 2012)
You and your oxygen unit