Comatose cardiac arrest patients need more time to awake

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Physicians should allow out-of-hospital comatose cardiac arrest patients treated with therapeutic hypothermia much more time to awake before drawing conclusions about survival outcomes, a University of Arizona study found.

Physicians may be drawing conclusions too soon about survival outcomes of patients who suffered a cardiac arrest outside the hospital. A study led by Dr Bentley Bobrow professor at the University of Arizona, Colleges of Medicine in Tucson and Phoenix and co-director of the Arizona Emergency Medicine Research CentrePhoenix, and his fellow UA emergency medicine researchers, showed that physicians may need to allow comatose cardiac arrest patients much more time to awake before making a prognosis.

More than 400,000 Americans experience out-of-hospital cardiac arrest annually. Survival statistics are bleak: although approximately 50% of people who arrest are revived after attempted resuscitation, only about 10% of these survive to leave the hospital. Furthermore, almost half of the survivors suffer some level of brain impairment from hypoxia (when the brain is not getting enough oxygen).

While out-of-hospital cardiac arrest is still a leading cause of death in the US, outcomes have improved dramatically in places like Arizona, where the focus has been on innovative healthcare advances, Bobrow said. Advances include compression-only CPR training for the public, enhanced telephone-CPR instructions and training for 911 dispatchers, implementing high-performance CPR for EMS providers and making sure patients are taken to specialised hospitals that deliver treatments like targeted therapeutic hypothermia to improve brain recovery.

Results from the multi-centre study showed for out-of-hospital cardiac arrest patients, the time it takes to regain consciousness after re-warming from therapeutic hypothermia treatment varies widely and is longer than many had thought.

“Most patients are comatose after resuscitation and accurately predicting those who will wake up can be extremely challenging,” Bobrow said. “There are many factors involved, but we know that it is common for doctors to try to decide who will and who won’t wake up after 24 to 48 hours of hospitalisation. However, our study found that a substantial number of cardiac arrest victims wake up longer than many people would expect. Sometimes they awaken from coma five, six or seven days after being admitted to the hospital and many of these have a good neurological outcome,” he said.

Among 573 out-of-hospital cardiac arrest patients who completed targeted temperature management, 60 woke up at least 48 hours after re-warming. Eight patients became responsive more than seven days after re-warming, six of whom were discharged with good neurological scores. One of the important findings was no predictive factors reliably identified who would awaken early or late.

Bobrow said, “We were surprised by the large proportion of cardiac arrest survivors who woke up more than three days after their arrest and went home with their families.

“While targeted therapeutic hypothermia has been shown to improve outcomes, no validated system currently exists for predicting when patients receiving this treatment will awaken from coma. Physicians and family members may need to wait longer than the traditional three days before making irrevocable decisions about brain function recovery and possible withdrawal of care,” he said.

“Our study quantifies the timing of awakening from a coma after cardiac arrest in the era of targeted temperature management, and this timing is much different than before we had this treatment,” said Dr Daniel Spaite, UA professor and Virginia Piper distinguished chair of emergency medicine.

“We may be able to save thousands of lives each year across the country by simply giving cardiac arrest victims more time to awaken in the hospital,” said Dr Samuel Keim, professor and chair of the UA department of emergency medicine.

Study objective: We evaluate the time to awakening after out-of-hospital cardiac arrest in patients treated with targeted temperature management and determine whether there was an association with any patient or event characteristics.
Methods: This was a prospective, observational cohort study of consecutive adult survivors of out-of-hospital cardiac arrest of presumed cardiac cause who were treated with targeted temperature management between January 1, 2008, and March 31, 2014. Data were obtained from hospitals and emergency medical services agencies responding to approximately 90% of Arizona’s population as part of a state-sponsored out-of-hospital cardiac arrest quality improvement initiative.
Results: Among 573 out-of-hospital cardiac arrest patients who completed targeted temperature management, 316 became responsive, 60 (19.0%) of whom woke up at least 48 hours after rewarming. Eight patients (2.5%) became responsive more than 7 days after rewarming, 6 of whom were discharged with a good Cerebral Performance Category score (1 or 2). There were no differences in standard Utstein variables between the early and late awakeners. The early awakeners were more likely to be discharged with a good Cerebral Performance Category score (odds ratio 2.93; 95% confidence interval 1.09 to 7.93).
Conclusion: We found that a substantial proportion of adult out-of-hospital cardiac arrest survivors treated with targeted temperature management became responsive greater than 48 hours after rewarming, with a resultant good neurologic outcome.

Taro Irisawa, Tyler F Vadeboncoeur, Madalyn Karamooz, Margaret Mullins, Vatsal Chikani, Daniel W Spaite, Bentley J Bobrow

University of Arizona material
Annals of Emergency Medicine abstract

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