Paramedics have for decades injected heart attack victims with adrenaline to help keep them alive. But new evidence suggests that the drug only slightly raises their survival odds — while greatly increasing the chances of devastating brain damage.
"It does increase the chances of making it to the hospital with a pulse," emergency medicine specialist Kyle Kelson of the SUNY Downstate Medical Center told BuzzFeed News. "But based on the data, it does have the strong potential of long-term harm."
In the US, around 350,000 people a year have cardiac arrests outside of the hospital and deaths occur 89% of the time. CPR and defibrillator shocks that are performed as quickly as possible give them the best chance at life.
Adrenaline, also called epinephrine, is only used when those steps fail as a last-ditch effort. It works by increasing blood pressure and hopefully restarting the heart. (It’s the same drug that reverses serious allergic reactions.)
In a new analysis published in the Academic Emergency Medicine journal, Kelson and his colleague Ian deSouza reviewed 13 studies of a combined 656,000 heart attack patients. The researchers found "no benefits" to giving epinephrine injections to heart attack victims outside of the hospital. (Using it in a hospital is less of a problem due to better monitoring of patients.)
Supporting this conclusion, a July report in the New England Journal of Medicine of patients in the UK found only a slight benefit to adrenaline shots in emergency heart attacks, 3.2% against 2.4% survival. It also found that among the people who survived, 31% of those who received adrenaline had "severe neurologic impairment," compared with 18% of those who did not get the shot. This meant that they often became bedridden, incontinent, or unable to walk unassisted.
Experts say that adrenaline is probably restarting the hearts of people who have been deprived of oxygen for too long, which saves their lives but only after the brain has been irreversibly damaged.
"One interpretation is that epinephrine can save the heart, but is too little, too late for the brain," said Clifton Callaway of the University of Pittsburgh Medical Center, who cowrote an editorial about the July study.
"Surprisingly, use of epinephrine all this time was based on laboratory experiments, and not on controlled clinical trials," he added, which might explain the debate happening only now, 50 years after the drug started being used in this way.
Adrenaline was established as a heart attack treatment in lab experiments on dogs in the 1960s, Kelson noted. Scientists in these experiments were simply looking for a restoration of a pulse. (But even then it was an established phenomenon: A surgeon first reported the restorative effect in 1903.) Neurologic complications were never investigated in people, largely because ethics rules precluded denying heart attack victims what could be a life-saving treatment.
That leaves the medical field looking back now at results from only actual heart attack victims and raising doubts about adrenaline.
In 2015, the International Liaison Committee on Resuscitation, which helps set standards for heart attack responses, called for further study of adrenaline shots, noting the very weak evidence for their use. The group will now look at creating new standards, it said in a July statement.
"Changing a recommendation, particularly one that is almost 50 years old, should be a careful, deliberate process," Callaway said. "Right now you are seeing the public discussion phase."
For now, whether paramedics should or shouldn’t use adrenaline "is almost a moral decision," Kelson said. "Discharging patients with a severe neurological injury is not the point of patient-centered care."