Recognition of cardiac arrest and prompt application of CPR and defibrillation gives best chance of survival

A new trial has confirmed that high quality CPR and the prompt use of a defibrillator are the best treatments for cardiac arrest in the community, underlining the critical importance of members of the public being trained in these lifesaving skills.

The UK trial which looked at the use of adrenaline in pre-hospital cardiac arrests, revealed that members of the public who are trained in CPR can make a significant difference to patient survival.

According to 2016 Out of Hospital Cardiac Arrest Register (OHCAR) for Ireland, there were 2,389 cases of cardiac arrests in the community where resuscitation was attempted and of these 7.8 per cent survived.

The best chance of survival comes if the cardiac arrest is recognised quickly, someone starts CPR and defibrillation (electric shock treatment) is applied without delay. Current guidelines advise that adrenaline is given if these initial treatments are unsuccessful.

The application of adrenaline is one of the last things tried in attempts to treat cardiac arrest. It increases blood flow to the heart and increases the chance of restoring a heartbeat. However, it also reduces blood flow in very small blood vessels in the brain, which may worsen brain damage. Observational studies, involving more than 500,000 patients, have reported worse long-term survival and more brain damage among survivors who were treated with adrenaline.

Therefore the “Pre-hospital Assessment of the Role of Adrenaline: Measuring the Effectiveness of Drug administration In Cardiac arrest (PARAMEDIC2)” trial was undertaken to determine if adrenaline was beneficial or harmful as a treatment for out of hospital cardiac arrest.

The trial ran from December 2014 through October 2017 and was conducted in 5 National Health Service Ambulance Trusts in the UK and included 8,000 patients in cardiac arrest. Patients were allocated randomly to be given either adrenaline or a salt-water placebo and all those involved in the trial including the ambulance crews and paramedics were unaware which of these two treatments the patient received.

Of 4,012 patients given adrenaline, 130 (3.2%) were alive at 30 days compared with 94 (2.4%) of the 3,995 patients who were given placebo. However, of the 128 patients who had been given adrenaline and who survived to hospital discharge, 39 (30.1%) had severe brain damage, compared with 16 (18.7%) among the 91 survivors who had been given a placebo.

In this study a poor neurological outcome (severe brain damage) was defined as someone who was in a vegetative state requiring constant nursing care and attention, or unable to walk and look after their own bodily needs without assistance.

The reasons why more patients survived with adrenaline and yet had an increased chance of severe brain damage are not completely understood. One explanation is that although adrenaline increases blood flow in large blood vessels, it also impairs blood flow in very small blood vessels and may worsen brain injury after the heart has been restarted. An alternative explanation is that the brain is more sensitive than the heart to periods without blood and oxygen and although the heart can recover from such an insult, the brain is irreversibly damaged.

Overall the trial found that the use of adrenaline in cardiac arrests results in less than 1 per cent more people leaving hospital alive – but almost doubles the risk of severe brain damage for survivors of cardiac arrest. The research raises important questions about the future use of adrenaline in such cases and will necessitate debate amongst healthcare professionals, patients and the public.

It also revealed that early recognition of a cardiac arrest and calling for an ambulance was 10 times more effective than adrenaline while CPR and defibrillation were 10 and 20 times more effective than adrenaline respectively.

According to Professor Jerry Nolan, from the Royal United Hospital Bath and a co-author on the paper, “This trial has answered one of the longest standing questions in resuscitation medicine. Taking the results in 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 recognise cardiac arrest, perform CPR and deliver an electric shock with a defibrillator. ”

Commenting on the trail results, Brigid Sinnott, Basic Life Skills (BLS) Co Ordinator with the Irish Heart Foundation said, “This study once again highlights the importance of everyone attempting CPR and using an AED if there is one available. Practising CPR regularly improves the quality of your CPR and improves your confidence in responding in the event of a cardiac arrest. In the past there was a lot of emphasis on delivering drugs and advanced measures however this study again brings us back to the importance of the simple techniques.”

The results of the trial were published in the New England Journal of Medicine (NEJM) on Thursday 19th July 2018 in an article entitled “A Randomized Trial of Epinephrine in Out-of-Hospital Cardiac Arrest”. The trial was funded by the National Institute for Health Research, sponsored by the University of Warwick and led by researchers in the University’s Clinical Trials Units – part of Warwick Medical School.