Landmark International ICU Study Delivers Major Post-Cardiac Arrest Care Finding

The high-profile collapse of Danish footballer Christian Eriksen during a recent European match reminds us how crucial decisions made following cardiac arrest can save lives.

In New Zealand, half of those who survive cardiac arrest and reach hospital remain critically ill and require Intensive Care Unit (ICU) support.

A five-year study, undertaken across Europe, North America, Australia, and New Zealand, and led here in Aotearoa by the Medical Research Institute of New Zealand (MRINZ) has explored whether controlling body temperature as a part of standard care to prevent brain damage for those who survive a cardiac arrest improves patient outcomes.

Recently announced ‘Targeted Hypothermia versus Targeted Normothermia after Out-of-Hospital Cardiac Arrest’ trial (TTM-2) results have conclusively proven that cooling survivors of cardiac arrest to below a normal body temperature does not improve their rates of recovery. These findings will very likely result in significant changes to standard clinical practice both here in Aotearoa New Zealand and internationally.

THE ‘CHAIN OF SURVIVAL’

On Saturday, 14 June 2021, millions of spectators watched in alarm as 29-year-old Danish footballer Christian Eriksen suffered a cardiac arrest and collapsed on the field in the middle of a UEFA European Championship game.

Christian’s heart had stopped, and he collapsed unconscious immediately. His collapse was witnessed, and he received prompt CPR. A defibrillator was used to restart his heart and he rapidly recovered consciousness.

Christian Eriksen is now in a stable condition in a hospital in Copenhagen, thanks to receiving immediate life-saving medical attention through the ‘Chain of Survival’.

Surviving a cardiac arrest depends on a ‘Chain of Survival’:

1. Recognition of cardiac arrest and activation of the emergency response system

2. Early cardiopulmonary resuscitation (CPR) with an emphasis on chest compressions

3. Rapid defibrillation

4. Advanced resuscitation by Emergency Medical Services and other healthcare providers

5. Post-cardiac arrest care in an inpatient critical-care facility with a comprehensive care plan

6. Recovery including additional treatment, observation, rehabilitation, and psychological support
 

A strong ‘Chain of Survival’ can greatly improve chances of survival and recovery for victims of cardiac arrest. Almost 1 in 3 cardiac arrests happen in a public place and performing CPR increases the chance of survival, as bystander CPR is a vital link in the ‘Chain of Survival.’ 
 

Christian Eriksen was lucky, as for him, the ‘Chain of Survival’ was strong. Most patients who suffer a cardiac arrest are not this fortunate.

Each week, in New Zealand, between 5 and 10 patients who have suffered from a cardiac arrest end up unconscious and on life support in an intensive care unit (ICU). Around half of these patients suffer permanent brain damage and either end up dependent or die as a consequence of their cardiac arrest. For these patients, ‘Post-cardiac arrest care' is a critical link in the ‘Chain of Survival’.

MAJOR NEW POST-CARDIAC ARREST CARE FINDING

Since 2002, patients who are unconscious after a cardiac arrest have routinely been cooled down to as low of 32°C to try to limit brain injury. Such ‘therapeutic hypothermia’ has been a cornerstone of ‘Post-cardiac arrest care’ for the past 20 years, and an entire industry has developed around cooling devices.

This is because in 2002 two small clinical trials suggested this therapy might reduce death and the risk of brain damage in cardiac arrest patients who were in a coma. Patients have been maintained in an artificial coma for many days to cool the body to try and protect the brain. However, considerable uncertainty around this procedure remained. Dspite widespread use of temperature management, the quality of evidence for hypothermia in cardiac arrest has been low.

In 2013, the ‘Targeted Hypothermia versus Targeted Normothermia after Out-of-Hospital Cardiac Arrest’ trial (TTM-1) showed that cooling cardiac arrest patients to either 33°C or 36°C resulted in similar outcomes, but much remained to be learned about the best way to apply temperature management.

The TTM-2 trial, an international study undertaken across Europe, North America, Australia, and New Zealand, and led here in Aotearoa over five years by MRINZ has definitively shown that cooling survivors of cardiac arrest to below a normal body temperature does not improve patient outcomes. The trial findings, just published in the New England Journal of Medicine, have shown that therapeutic hypothermia is no more effective than treating fevers when they occur.

“Determining that therapeutic hypothermia is not an effective therapy for cardiac arrest patients is an incredibly important medical finding. It will allow clinicians to better focus their attention on other aspects of supportive care.” Professor Paul Young, MRINZ deputy director and TTM-2 International Trial Management Committee member and Lead New Zealand Investigator says, “Treating fevers is much more straight forward than artificially cooling a patient down, but the end of this therapeutic hypothermia era means that we are now in desperate need of new strategies to minimise the risk of brain damage among cardiac arrest survivors.”

MRINZ-led Research teams are currently engaged with two significant associated trials that are focused on the future of ‘Post-cardiac arrest care'. The TAME trial, which is looking at whether targeting higher than normal blood carbon dioxide levels can reduce brain damage after cardiac arrest; and the LOGICAL trial which is exploring whether avoiding exposure to abnormally high levels of oxygen after cardiac arrest can improve patient outcomes.

“The TTM-2, TAME and LOGICAL trials all offer MRINZ scientists significant opportunity to advance knowledge in this field, by collaborating with like-minded researchers internationally, who like us, are deeply committed to supporting clinicians worldwide to improve outcomes in critically ill patients.” Professor Richard Beasley, Director of the MRINZ, says “We’re particularly grateful to the Health Research Council of New Zealand for their support in these influential ICU focused investigations.”

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