MONDAY, Dec. 1, 2014 (HealthDay News) -- A shot of adrenaline can jumpstart a heart that's stopped beating and save a life -- think of Uma Thurman in "Pulp Fiction," near death from overdose and rescued by a hypodermic needle to the chest.
But adrenaline might also harm those it helps, says a new study from France.
Four out of five people who receive adrenaline to restart their heart end up suffering significant damage to brain function, the researchers found. The same level of brain damage occurs in only one-third of patients whose hearts restarted without help from adrenaline.
Further, chances of brain damage increased with the amount of adrenaline that patients received, the researchers reported in the Dec. 2 online edition of the Journal of the American College of Cardiology.
These findings should prompt a search for a better alternative to adrenaline, which also is called epinephrine, said Dr. Richard Chazal, medical director of the Lee Memorial Health System's Heart and Vascular Institute in Fort Myers, Fla.
"Epinephrine is probably not the perfect agent, and so this really amplifies the need for further research to clarify if there is a better agent or combination of agents," said Chazal, who is also vice president of the American College of Cardiology. "There isn't a good alternative right now, but this certainly points out that we need to find better options."
Adrenaline is a hormone that stimulates the heart and promotes blood flow. It is a proven life-saving treatment for people whose hearts can't be restarted by electrical shocks from a defibrillator, Chazal said.
However, doctors have been concerned that adrenaline might also harm the brain and other parts of the body by rushing blood back into tissues that have been starved of oxygen, the researchers explained in background information in the study.
Each year, more than 420,000 cardiac arrests occur in the United States, according to the American College of Cardiology. Most are caused by an abnormality in the heart's rhythm, which can result from numerous diseases.
In this study, French researchers analyzed hospital records for more than 1,500 people admitted to a large Paris hospital over 12 years. All had suffered cardiac arrest outside a hospital but had been resuscitated. Nearly three-quarters had received at least one dose of adrenaline.
The researchers focused on people who left the hospital with normal or only moderately compromised brain function as a result of their cardiac arrest. They found that 63 percent of patients who did not receive adrenaline left with relatively healthy brains, compared to only 19 percent of those who got one or more shots of adrenaline.
Patients receiving higher doses of adrenaline fared worse than those with lower doses, the investigators found. Current international guidelines recommend administering 1 milligram of epinephrine every 3 to 5 minutes during resuscitation, the researchers noted.
Compared to patients who received no adrenaline, those receiving 1-milligram doses were 52 percent more likely to suffer brain damage, and those receiving 5-milligram or larger doses were 77 percent more likely, the study found.
Timing also proved a factor, with patients more likely to have a bad outcome if they received adrenaline later in their resuscitation.
"The role of epinephrine is more and more questionable in cardiac arrest," study lead author Dr. Florence Dumas, of the Parisian Cardiovascular Research Center in France, said in a news release. "We need to constantly assess our procedures and protocols to make sure that the use of epinephrine is effective and done at the correct time."
This leaves emergency workers and physicians in a jam, Chazal said. Adrenaline is a proven life-saver, and must be used if patients aren't responding to defibrillation.
"Until we have better agents, the primary goal is to get the person to survive," he said. "We don't want a first responder or medical professional standing there with a patient who hasn't responded to defibrillation and hesitate in the use of epinephrine because of this study, because according to this study the earlier you give it, the better."
The study emphasizes the importance of alternatives to adrenaline, said Dr. Robert Glatter, an emergency physician at Lenox Hill Hospital in New York City. These include "prompt defibrillation with quality chest compressions, two interventions which have shown benefit in the early management of patients in cardiac arrest," he said.
For more on cardiac arrest, visit the U.S. National Library of Medicine.