Cognitive impairments in survivors of out-of-hospital cardiac arrest: a systematic review.

OBJECTIVE To describe the current evidence on the frequency and nature of cognitive impairments in survivors of out-of-hospital cardiac arrest. DESIGN Systematic review. DATA SOURCES Pubmed, Embase, PsychInfo and Cinahl (1980-2006). No language restriction was imposed. REVIEW METHODS The following inclusion criteria were used: participants had to be survivors of out-of-hospital cardiac arrest, 18 years or older, and there had to be least one cognitive outcome measure with a follow-up of 3 months or more. Case reports and qualitative studies were excluded. The articles were screened on title, abstract and full text by two reviewers. All selected articles were reviewed and assessed by two reviewers independently using a quality criteria list. RESULTS Out of the 286 articles initially identified, 28 were selected for final evaluation. There was a high heterogeneity between the studies with regard to study design, number of participants, outcome measures and duration of follow-up. In general, the quality of the articles appeared low, with a few positive exceptions. The reported frequency of cognitive impairments in survivors of out-of-hospital cardiac arrest ranged from 6% to 100%. Memory problems were the most common cognitive impairment, followed by impairments in attention and executive functioning. Three high-quality prospective studies found that cognitive problems occurred in about half of the survivors of out-of-hospital cardiac arrest. CONCLUSION There are few good studies on the frequency of cognitive impairments after out-of-hospital cardiac arrest. However, cognitive problems, in particular memory problems, seem common in survivors of out-of-hospital cardiac arrest.