Nearly 383,000 out-of-hospital sudden cardiac arrests occur annually. Of those who survive a cardiac arrest, mild-to-moderate cognitive impairment is common; half of all those who survive experience problems with cognitive functions such as memory and attention. One of the primary factors limiting full recovery after successful cardiopulmonary resuscitation (CPR) is the brain's ability to tolerate the insult of global ischemia that occurs at the time of resuscitation.

Previous studies have revealed that survivors of cardiac arrest showed low test performances in attention, learning and memory, executive functioning, and that neuropsychological bedside screening during the first month significantly differentiated between patients with and without long-term cognitive impairment.

However, in a recent study, a control group comprising heart attack patients had largely the same level of problems, which suggests that it is not only the cardiac arrest and the consequent lack of oxygen to the brain that is the cause of the patients' difficulties. The importance of this study was that brain injury affects neurologic function and quality of life in survivors after cardiac arrest. The main aim of the study was to compare the effect of a body temperature of 33 degrees Celsius and 36 C following cardiac arrest. The researchers have previously shown that maintaining a temperature of 36 C produced the same survival rate as cooling to 33 C.

The study, led by Dr. Tobias Cronberg, associate professor at Lund University in Sweden and consultant neurologist at Skåne University Hospital in Lund, involved 950 cardiac arrest patients in Europe and Australia. Six months after the cardiac arrest, half of the patients had died, and the survivors were followed up with cognitive screening tests. Both the patients and their relatives were also asked to report changes that had taken place following the cardiac arrest.

Almost 300 cardiac arrest survivors also underwent more detailed tests. Their results were compared with a control group made up of heart attack patients. Cognitive function was measured by the Mini-Mental State Examination (MMSE) and assessed by observers through the Informant Questionnaire on Cognitive Decline in the Elderly (IQCODE). Patients reported their activities in daily life and mental recovery through Two Simple Questions and their quality of life through the Medical Outcomes Study 36-Item Short Form Health Survey, version 2.

The researchers expected there would be a clear difference between the groups because the heart attack patients had not been exposed to any oxygen deficiency in the brain. However, they had signs of mild brain damage to almost the same extent as the cardiac arrest patients.

According to Dr. Cronberg, survival in itself probably plays an important part in this: The patients know that they have come close to dying and are grateful to still be alive.

This study demonstrated that not only survival but also cognitive ability is the same in patients who have been kept at 33 C or 36 C, important for the results previously reported.

All in all, patients as well as their relatives have appreciated the opportunity to discuss any deterioration, its causes and how it can be addressed, indicating the benefits of providing follow-up care to all cardiac arrest patients not only with regard to physical health but also with regard to memory and attention.