Fecal Microbiota Transplantation for the Treatment of ICU Delirium

Delirium in the intensive care unit (ICU) is a prevalent and serious neurological complication among critically ill patients, with large multicenter studies reporting an incidence of 30% to 80%, particularly in those requiring mechanical ventilation. Delirium is not only associated with prolonged ICU and hospital stays but also with increased morbidity and mortality. Notably, up to 40% of survivors suffer from persistent cognitive dysfunction that may last for months or even years. Despite current standard pharmacological interventions-such as haloperidol and second-generation antipsychotics-failing to demonstrate significant clinical benefit in phase III trials, non-pharmacological strategies remain challenging to implement due to environmental and operational constraints within the ICU. This unmet clinical need underscores the imperative to develop novel, effective therapeutic approaches. Emerging evidence suggests that ICU-acquired gut microbiota dysbiosis plays a pivotal role in the pathogenesis of delirium. Dysbiosis can compromise intestinal barrier integrity, promoting systemic inflammation and increasing susceptibility to various forms of delirium, including acute illness-related and postoperative types. These effects are likely mediated through the "gut-microbiota-brain axis," which may represent a central mechanism underlying neurocognitive dysfunction in critical illness. Preclinical studies have demonstrated that fecal microbiota transplantation (FMT) can restore microbial balance and exert beneficial effects on neurological function. FMT has shown promise in ameliorating cognitive deficits in models of Alzheimer's disease, chronic cerebral hypoperfusion, traumatic brain injury, and chronic unpredictable mild stress (CUMS). Clinically, FMT has been associated with cognitive improvement in patients with dementia, recurrent Clostridioides difficile infection, and sepsis-associated encephalopathy. With expanding applications in both gastrointestinal and e