Cognitive function after cardiac arest and targeted temperature management

This thesis focuses on cognitive impairment in Out-of-Hospital Cardiac Arrest (OHCA) survivors with the main aim
to evaluate possible effects by targeted temperature management. Secondary aims are to describe the prevalence of
cognitive impairment in a large group of OHCA-survivors, the related symptoms of psychological distress and the
actual effect of cognitive impairment for the patient’s ability to participate in everyday life and in the society (as
work).
Methods: In an international trial, OHCA-patients, unconscious after resuscitation, were randomized to 33°C or
36°C controlled temperature. Survivors were invited to a face-to-face follow-up 180 days post-arrest that included
screening of cognitive impairment (MiniMental Status Examination), questionnaires of cognitive performance in
everyday life (Two Simple Questions, Informant Questionnaire on Cognitive Decline) and Health Related Quality
of Life (HRQoL) (Short Form Questionniare-36 version2®). An extended follow-up was performed at 20 sites in
five countries and included assessments of memory (Rivermead Behavioural Memory Test), executive functions
(Frontal Assessment Battery), attention/processing speed (Symbol Digit Modalities Test), psychological distress
(Hospital Anxiety and Depression Scale) and participation (Mayo-Portland Adaptability Inventory-4). A matched
control group of ST-elevation myocardial infarction (STEMI) patients performed the same follow-up.
Results: OHCA-survivors (n=287) had overall good outcome and HRQoL, but half reported a decreased
participation in everyday life and society. In addition, many informants (62%) and patients (36%) reported cognitive
problems, and 27% of survivors reported psychological distress. By objective assessments cognitive impairment
was found in >50% of the survivors, and OHCA-survivors with cognitive impairment had an increased risk of being
on sick leave. Cognitive impairment, depression, fatigue, and mobility restrictions were found important for
participation in everyday life and in the society There were no differences in any of these outcomes between the two
temperature groups (33°C and 36°C). Cognitive impairment and psychological distress was common also among
STEMI-controls (n=119), but OHCA-survivors had significantly more problems with attention/processing speed,
return to work and participation compared to STEMI-controls.
Conclusion. The two groups of TTM at 33°C and 36°C were similar also when brain injury is assessed in detail
indicating no difference in outcome. Cognitive impairment was common in OHCA-survivors but STEMI-controls
shared many of the symptoms and that impairment after OHCA needs to be seen in a greater context of risk factors
including OHCA-related brain injury, cardiovascular co-morbidity, and critical illness related stressors. OHCAsurvivors
had lower participation in everyday life compared to STEMI-controls. A structured follow-up to identify
OHCA-survivors in risk for long-term consequences is recommended. Cognitive impairment, fatigue, mobility
restrictions and depression deserve increased attention during such follow-up.