Postoperative Delirium After Cardiac Surgery: Psychiatric Vulnerability, Biological Mechanisms, and Prevention Strategies

INTRODUCTION: Delirium is one of the most common and serious neuropsychiatric complications following cardiac surgery. It is associated with increased mortality, prolonged intensive care unit (ICU) and hospital stay, long-term cognitive decline, and reduced quality of life. AIMS AND OBJECTIVES: The aim of this study is to synthesize current evidence on the epidemiology, psychiatric and psychosocial risk factors, biological mechanisms, perioperative modifiers, prevention strategies, and long-term outcomes of delirium after cardiac surgery, with particular emphasis on its role as a marker of brain vulnerability. MATERIALS AND METHODS: A narrative literature review was conducted using articles published between 1990 and 2025, identified through the PubMed and ScienceDirect databases. The search strategy included the terms "delirium," "cardiac surgery," "psychiatric disorders," and "cognitive impairment." RESULTS: Recent evidence suggests that approximately one quarter of patients undergoing cardiac surgery develop delirium, with hypoactive forms frequently remaining underrecognized in clinical practice. Pre-existing depression, cognitive impairment, substance use disorders, low educational level, frailty, and social isolation significantly increase the risk of postoperative delirium. Within a stress-diathesis framework, peripheral physiological insults may be reflected centrally as acute brain dysfunction in vulnerable individuals. Modifiable perioperative factors include sedative choice and depth, as well as sleep and circadian disruption. Multicomponent non-pharmacological interventions, early mobilization, structured psychiatric and cognitive screening, and dexmedetomidine-based sedation have demonstrated consistent efficacy in reducing the incidence and/or duration of delirium. Furthermore, delirium has been associated with persistent cognitive and psychiatric morbidity, functional decline, and increased long-term mortality. CONCLUSIONS: Delirium following cardiac surgery is a multifactorial syndrome with significant short- and long-term consequences. A comprehensive, multidisciplinary approach integrating biological, psychiatric, and perioperative perspectives is essential for effective risk stratification, prevention, and long-term follow-up.