July 3 (HealthDay News) -- Injecting the artery-constricting hormone vasopressin in addition to adrenaline did not improve survival among people who had sudden cardiac arrest in an European trial, but American cardiologists said the finding does not rule out use of that treatment in some cases.

The report comes from a group, primarily French, that several years ago described promising results of combining vasopressin and epinephrine -- the formal name of adrenaline -- as part of the emergency treatment of cardiac arrest. The American Heart Association responded to that report in guidelines saying that a first shot of vasopressin might be substituted for adrenaline, the traditional drug for cardiac arrest, in some cases.

But the latest report, on a total of nearly 3,000 people, found that "the combination of vasopressin and epinephrine during advanced cardiac life support for out-of-hospital cardiac arrest does not improve outcome." The study was published in the July 3 issue of the New England Journal of Medicine.

In each group, about one in five of those treated survived long enough to be admitted to a hospital -- 20.7 percent of the combined therapy group, 21.3 percent of the adrenaline-only group. The one-year survival rate was 1.3 percent for those given the two drugs, 2.1 percent of those given only adrenaline.

The reason for not giving up entirely on vasopressin is due to the average response time in the French study, said Dr. Joseph P. Ornato, chairman of emergency medicine at Virginia Commonwealth University, and a member of the committee that drew up the heart association guidelines.

"Paris is a city with a lot of traffic," Ornato said. "If you look at the time of collapse to the time of treatment, the first crew was at the scene in an average of 7.2 minutes. They didn't start to treat until 16.3 minutes. The first steady drug injection was not until 21 minutes."

That interval means everything, because "we lose roughly 10 percent of the odds of the resuscitation every minute," Ornato said.

In Richmond, "90 percent of the time, we respond within eight minutes or less," he said.

And so, Ornato said, "I am less than convinced that this completely answers the question, because I don't know what it means when your drugs don't start until 20 minutes after the heart has stopped."

The trial "raises as many questions as it answers," said Dr. Nisha Chandra-Strobos, chief of cardiology at the Bayview division of Johns Hopkins University.

The slow response time is one major reason, she said: "A time to injection of 21 minutes, the game is really over at that time."

The heart association guidelines which Ornato helped prepare apply only to the medical personnel called for emergency treatment of cardiac arrest. The heart association advises persons without medical training to call for that help as quickly as possible by dialing 911.

Emergency measures can be taken before medical help arrives. Newly updated advice by the heart association says that simply depressing the chest periodically and continually can contribute to survival. If the cardiac arrest occurs in a public place such as an airport, a portable defibrillator may be available. It should be placed against the chest to deliver an electric shock that might start the heart beating again.

SOURCES: Joseph P. Ornato, M.D., chairman, emergency medicine, Virginia Commonwealth University, Richmond, Va.; Nisha Chandra-Strobos, M.D., chief, cardiology, Johns Hopkins Bayview, Baltimore; July 3, 2008, New England Journal of Medicine