NEW YORK (Reuters Health) - People who've suffered cardiac arrest usually get a shot of adrenaline to help their heart back on track, but in a controversial study from Australia the hormone did little to increase patients' survival.
Researchers did find, however, that those who received adrenaline -- also called epinephrine -- were more likely to have their heart pumping again before they reached the hospital than patients who did not get the shot, a result that the researchers say supports the use of adrenaline.
"My guess is (the study) probably is not going to change how we practice currently, but it may stimulate a larger study on the role of epinephrine in out-of-hospital cardiac arrests," said Dr. Gordon Tomaselli, the president of the American Heart Association and the director of the Division of Cardiology at Johns Hopkins University School of Medicine, who was not involved in this new work.
For decades, adrenaline has been part of standard practice for attempting to revive patients who experience cardiac arrest in the United States and elsewhere, though there have been no studies that compare the health effects of patients who receive adrenaline versus those who don't.
During cardiac arrest, the heart stops pumping out blood. Nearly 300,000 people outside of hospitals suffer a cardiac arrest each year in the U.S., and the outcome is fatal in about 90 percent of cases.
In the new study, published in the journal Resuscitation, researchers equipped ambulances in Western Australia with either doses of adrenaline or a saline solution.
More than 500 patients received either adrenaline or saline as emergency teams attempted to save their lives.
Among those who got saline, 22 had their hearts pumping blood before they arrived at the hospital, while 64 in the adrenaline group achieved circulation.
Five of the patients in the saline group survived and were discharged from the hospital, while 11 from the adrenaline group survived and were discharged.
Though the adrenaline group had more than double the number of survivors, statistical tests showed the difference could have been due to chance.
"Although the results were statistically negative on the important outcomes, the trend was in the right direction," Tomaselli told Reuters Health.
Dr. Ian Jacobs, the lead author of the study and a professor at the University of Western Australia, told Reuters Health in an email that adrenaline should still be part of routine care.
"This is particularly so as we further identify and understand those post (return-to-circulation) factors which contribute to survival," Jacobs said.
Jacobs also said he expects that, had he been able to include more patients in the study, he might have found an actual improvement in survival from adrenaline.
But he and his colleagues had difficulty getting additional ambulance crews to participate.
"In short, the fact that adrenaline was considered standard of care -- albeit unproven -- some paramedics felt that this trial was unethical and went to the media," Jacobs said. Ultimately, those paramedics did not participate.
He said that the Human Research Ethics Committee under the Australian National Health and Medical Research Council, which funded the study, provided the researchers with a waiver for consent from the patients to participate. Ordinarily, researchers are required to get informed consent from patients before enrolling them in a medical experiment.
The study was approved by "numerous Human Research Ethics Committees, Guardianship Boards and Departments of Crown Law," Jacobs added.
Consent from patients in an emergency setting is very difficult, Tomaselli said, which explains why there have been no studies like this to date.
"If we say, 'because you can't get consent, you can't do any studies,' then we should give up on any studies in cardiac arrest at all. I don't think that's the way we should go," Tomaselli said.
SOURCE: http://bit.ly/oagQAJ Resuscitation, online July 2, 2011.
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