December 1st, 2014
Study Suggests Epinephrine for Cardiac Arrest May Be Harmful
Epinephrine has been a cornerstone of therapy during cardiac resuscitation after cardiac arrest because of its well-established ability to stimulate the heart and increase the probability of a return of spontaneous circulation (ROSC). In recent years, however, concerns have been raised that people treated with epinephrine may have worse neurological outcomes following their resuscitation.
In a study published in the Journal of the American College of Cardiology, French researchers analyzed data from more than 1,500 patients who were successfully resuscitated after an out-of-hospital cardiac arrest and were subsequently treated at a large hospital in Paris. A total of 73% received epinephrine during resuscitation. The two groups were different in a number of respects: patients who received epinephrine were older, had a longer resuscitation, were less likely to have had a witnessed event, and were less likely to have had a shockable rhythm.
In the entire study group 31% survived to hospital discharge and 29% survived with a good neurological outcome. However, patients in the epinephrine group were less likely to have survival with a good neurological outcome (17% of patients in the epinephrine group versus 60% in the no epinephrine group).
This difference remained significant after adjusting for known differences between the groups. The researchers also reported that in a subset of the study population involving 228 matched pairs, epinephrine-treated patients were again less likely to have a good outcome. The authors acknowledged the criticism that epinephrine could be “considered a surrogate marker of severity rather than an independent predictive factor” but said that their “multiple methodological efforts” to remove bias led to their robust findings.
Early use of epinephrine within the first nine minutes of treatment was associated with a better outcome than later use of epinephrine. The authors suggested that epinephrine may not be helpful in the very early “electrical” phase of cardiac arrest and that the vasopressor effect of the drug may be harmful in the late “metabolic” stage. But epinephrine may still be helpful in the middle “circulatory” phase, they speculate.
“The role of epinephrine is more and more questionable in cardiac arrest,” said the first author of the study, Florence Dumas, of the Parisian Cardiovascular Research Center in France.
“It’s very difficult, because epinephrine at a low dose seems to have a good impact in the first few minutes, but appears more harmful if used later,” said Dumas. “It would be dangerous to completely incriminate this drug, because it may well be helpful for certain patients under certain circumstances. This is one more study that points strongly to the need to study epinephrine further in animals and in randomized trials.”
In an accompanying editorial, Gordon Ewy writes that the study “adds to the concern that epinephrine is not the ideal vasopressor during resuscitation of patients.”