Predicting Long-Term Cognitive Impairments in Survivors after Cardiac Arrest: A Systematic Review

Objective: International guidelines recommend early screening for identification of patients who are at risk of long-term cognitive impairments after cardiac arrest. However, information about predictors is not provided. A systematic review of the literature was performed to identify early predictors of long-term cognitive outcome after cardiac arrest. Methods: Scopus and PubMed were systematically searched to identify studies on early predictors of long-term cognitive outcome in patients after cardiac arrest. The population included adult cardiac arrest survivors and potential early predictors were demographics, early cognitive screening scores, imaging measures, electroencephalographic measures, and levels of blood biomarkers. Two investigators reviewed studies for relevance, extracted data and assessed risk of bias. Results: Five articles were included. Risk of bias was assessed as low or moderate. Most detected longterm cognitive impairments were in the domain of memory. Coma duration (2 studies), early cognitive impairments by the self-developed clinical Bedside Neuropsychological Test Battery (BNTB) screener (2 studies), and high S-100B levels on day 3 (2 studies) were the most prominent identified determinants of cognitive impairment on the group level. On the individual patient level, a score on the BNTB of ≤ 94.5 predicted cognitive impairments at 6 months after cardiac arrest (1 study without external validation). Studies on brain imaging and electroencephalography are lacking. Conclusion: Early bedside cognitive screening can contribute to prediction of long-term cognitive impairment after cardiac arrest. Evidence is scarce for S-100B levels and coma duration and absent for measures derived from brain imaging and electroencephalography. LAY ABSTRACT Survival rates of patients after cardiac arrest have increased significantly over the past decades. However, many cardiac arrest survivors have impairments in different domains of thinking (memory, attention, and executive functions, such as planning). Early identification of survivors at risk of such impairments could guide personalized rehabilitation. However, such predictors are currently unavailable. This study reviewed the literature to identify possible early predictors for patients at risk of long-term impairments in thinking. A short, early, bedside test to screen domains of thinking during hospital admission may help to predict long-term impairments. Certain blood markers and a long duration of coma have also been associated with long-term impairments of thinking, but the evidence is weak. There are no studies on brain imaging and electroencephalography in this context.