Using adrenaline in cardiac arrest likely to cause brain damage : Landmark study

Treating cardiac arrest with adrenalin may nearly double the risk of permanent brain damage and only marginally improves the chances of survival, according to the findings of a trial recently published in the journal NEJM. The landmark study has found that although treatment given to thousands of people who suffer cardiac arrest in Britain every year adrenalin marginally improves the chances of survival but it doubles the risk of permanent brain damage.

Every year less than 1% of people survive cardiac arrest in the UK. The rate of survival depends only if the cardiac arrest is diagnosed quickly and cardiopulmonary resuscitation (CPR) and defibrillation (electric shock treatment) are applied immediately.

Adrenaline is the last weapon for the doctors in an attempt to treat cardiac arrest. It increases blood flow to the heart and increases the chance of restoring a heartbeat. On the other hand, it also reduces blood flow in very small blood vessels in the brain which may result in brain damage. Observational studies, involving more than 5 lakh patients, have reported worse long-term survival and more brain damage among survivors who were treated with adrenaline.

Gavin D. Perkins and his associates conducted a study to determine whether the use of epinephrine is safe and effective for out-of-hospital cardiac arrest patients.

The researchers conducted a randomized, double-blind trial involving 8014 patients with out-of-hospital cardiac arrest. Patients were randomly allocated with either adrenaline or a salt-water placebo.

The study found that of 4012 patients given adrenaline, 130 (3.2%) were alive at 30 days compared with 94 (2.4%) of the 3995 patients who were given a placebo.

At the time of hospital discharge, severe brain damage had occurred in more of the survivors in the epinephrine group than in the placebo group 31.0% vs17.8%.

No satisfactory explanation has been provided by the previous researchers as to why more patients survived with adrenaline and yet had an increased chance of severe brain damage. A probable explanation may be that though adrenaline increases blood flow in large blood vessels, on the contrary, it impairs blood flow in very small blood vessels and may worsen brain injury after the heart has been restarted.

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"We have found that the benefits of adrenaline are small - one extra survivor for every 125 patients treated - but the use of adrenaline almost doubles the risk of a severe brain damage amongst survivors." said the lead author Professor Gavin Perkins. He added "Patients may be less willing to accept burdensome treatments if the chances of recovery are small or the risk of survival with severe brain damage is high. Our own work with patients and the public before starting the trial identified survival without brain damage is more important to patients than survival alone. The findings of this trial will require careful consideration by the wider community and those responsible for clinical practice guidelines for cardiac arrest."

Professor Jerry Nolan, co-author of the study said "This trial has answered one of the longest standing questions in resuscitation medicine. Taking the results in the context of other studies, it highlights the critical importance of the community response to cardiac arrest. Unlike adrenaline, members of the public can make a much bigger difference to survival through learning how to recognize cardiac arrest, perform CPR and deliver an electric shock with a defibrillator. "

The study concluded that the use of adrenaline resulted in a significantly higher rate of 30-day survival than the use of placebo in adults with out-of-hospital cardiac arrest but more survivors had severe neurologic impairment in the adrenaline group.