Cognitive Outcomes Good With Hypothermia After Cardiac Arrest

March 20, 2013

Patients surviving out-of-hospital cardiac arrest have shown better survival if treated with therapeutic hypothermia, and initial data now suggest that most of the patients who do survive after hypothermia have preserved cognitive function and are able to return to work.

The cognitive function data were presented here at the American Academy of Neurology (AAN) meeting by Samuel Moore, MD, from the Mayo Clinic, Rochester, Minnesota.

"The use of hypothermia has improved the survival rate for resuscitated cardiac arrest patients from about 1 in 6 to around 1 in 2, and it has now become the standard of care for patients with resuscitated cardiac arrest," senior author of the study, Alejandro Rabinstein, MD, also from the Mayo Clinic, Rochester, explained to Medscape Medical News.

"That is wonderful, but hypothermia is a major endeavor and very costly. We want to make sure we are not saving a bunch of people who will be cognitively impaired. That doesn't seem to be the case."

He added, "Yes, some had cognitive impairment, but that has always been the case after resuscitated cardiac arrest. That percentage does not appear to be higher after hypothermia."

Gross Measure

Previous trials have shown that therapeutic hypothermia improves survival of patients with resuscitated cardiac arrest due to ventricular fibrillation, Dr. Rabinstein said, "but we haven't known what their cognitive function has been like. Studies so far have only assessed cerebral performance category, which is a gross measure of general function. It doesn't tell us much about cognitive function."

For the current study, 133 consecutive survivors of cardiac arrest who underwent therapeutic hypothermia from June 2006 to May 2011 were identified. Of these, 77 (58%) were alive at a mean follow-up of 21 months (range, 2 to 59 months). The researchers interviewed 56 patients (73% of those alive) by phone. Median age was 67 years (range, 24 to 88 years), and 51 (91%) were living independently.

Patients underwent the Telephone Interview for Cognitive Status (TICS-m), which Dr. Rabinstein described as a short simple cognitive tool. Results showed a median TICS-m score of 33 (range, 16 to 41).

Of the patients who took part, 33 (60%) were considered cognitively normal and 22 (40%) were mildly cognitively impaired. The time to assessment did not differ among the cognitive outcomes.

Of the 38 patients who were working up to the time of the cardiac arrest, 30 (79%) returned to work. Cognitive outcome was not associated with age, time to return of spontaneous circulation, brain atrophy, leukoaraiosis, or neuron-specific enolase level.

Cognitively Intact

Commenting on the study for Medscape Medical News, Victor W. Henderson, MD, Stanford University, California, said, "This large, consecutive case series examines cognitive outcomes among adults whose therapy after out-of-hospital cardiac arrest included hypothermia."

"Although outcomes may have been worse among survivors who did not participate in telephone cognitive assessments, overall findings support the important conclusion that many cardiac arrest survivors treated in this manner — regardless of age and regardless of time required to return to spontaneous circulation  — are cognitively intact and able to resume usual occupational activities," Dr. Henderson added. 

American Academy of Neurology (AAN) 65th Annual Meeting. Abstract S07.004. Presented March 19, 2013.