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 extraintestinal disorders, FMT has emerged as a transformative therapeutic modality, supported by robust short- and long-term safety and efficacy data.
This study aims to evaluate whether FMT can alleviate delirium severity, correct gut microbiota dysbiosis at 0, 72, and 120 hours post-enrollment, attenuate intestinal barrier dysfunction, reduce systemic inflammation and disease severity, shorten ICU length of stay, and lower rates of ICU mortality, in-hospital mortality, and 28-day all-cause mortality-ultimately positioning FMT as a potential breakthrough intervention for ICU delirium.
1. Age ≥ 18 years old, no ethnic or gender restrictions;
2. CAM-ICU-positive delirium;
3. Expected ICU stay ≥ 5 days after inclusion in the study;
4. Signed written informed consent.
Typical antipsychotics: Chlorprothixene, Flupentixol, Haloperidol, Levomepromazine, Loxapine, Melperone, Perphenazine, Pericyazine, Pimozide, Prochlorperazine, Zuclopenthixol, Pimavanserin, Sulpiride.
Atypical antipsychotics: Amisulpride, Aripiprazole, Asenapine, Clozapine, Lurasidone, Olanzapine, Paliperidone, Quetiapine, Risperidone, Sertindole, Ziprasidone. However, the non-habitual administration of antipsychotic medications in the general ward prior to the patient's ICU admission (e.g., for the management of delirium) is deemed acceptable. Nevertheless, antipsychotic therapy should be discontinued upon the patient's ICU admission.
2. Severe systemic infection in the early stage of resuscitation, hemodynamic instability or insufficient tissue perfusion, and severe imbalance of water, electrolyte and acid-base.
3. Patients with a high risk of death within 5 days as judged by the clinician, or those whose treatment decisions are restricted.
Single group
Intestinal microbiota suspension
Other interventionFMT was administered via a nasojejunal tube daily for three consecutive days, between 11:00 and 13:00. Each 50-100 mL dose, derived from 100-150 g of adolescent donor feces diluted to 300 mL. Patients fasted for 2 hours before and after FMT, except for permitted water intake. Intravenous antibiotics were withheld unless active infection was confirmed. If pathogens were considered colonizing and the patient remained stable, systemic antibiotics were avoided. Localized treatments, such as nebulized antibiotics, were allowed as needed. All antibiotic use required clinical justification and individual assessment to minimize interference with FMT. Oral antibiotics were prohibited after FMT initiation to protect engraftment and microbial integrity.
Delirium-free days (DFDs)
The CAM-ICU is a standardized tool specifically designed for the rapid screening of delirium in ICU patients. It achieves efficient diagnosis by evaluating indicators including consciousness state, attention, and disordered thinking. and perceptual abnormalities. Delirium can be diagnosed if features 1 and 2 are met, and at least 3 or 4 are present. The assessment process is standardized, and medical staff can operate independently after training. For patients who survived and were discharged from the ICU or hospital during the study observation period, the entire period subsequent to their discharge date shall be counted as delirium-free. For patients who died during the study observation period, the interval from their date of death to the end of the observation period shall be recorded as 0 delirium-free days. DFDs = Total observation days - Days with delirium - Days with coma - Days from death to the end of observation.
CAM-ICU-7 score
A 7-point rating scale (0-7) was derived from the CAM-ICU and RASS assessments. The final CAM-ICU-7 score ranges from 0-7 with 7 being most severe. CAM-ICU-7 scores were further categorized as 0-2: no delirium, 3-5: mild to moderate delirium, and 6-7: severe delirium.
Changes in intestinal microbiota composition
Metagenomic profiling of fecal samples obtained via rectal swabs to assess: Changes in alpha-diversity (Shannon index), beta-diversity (Bray-Curtis dissimilarity), and relative abundance of specific bacterial taxa.
Alterations in serum metabolites
Serum samples were collected for non-targeted metabolomics analysis to comprehensively examine the composition and changes of endogenous small molecule metabolites in the blood.
Acute Gastrointestinal Injury (AGI) Score
The AGI scoring system is a standardized tool in critical care for assessing gastrointestinal dysfunction severity. It divides injury into four grades based on clinical and physiological findings: Grade I involves partial gastrointestinal impairment, such as feeding intolerance or transient diarrhea; Grade II includes gastrointestinal dysfunction, like gastroparesis with aspiration risk or abdominal compartment syndrome; Grade III indicates gastrointestinal failure, marked by persistent feeding intolerance or intestinal ischemia; Grade IV features gastrointestinal failure with severe systemic consequences, including intestinal necrosis or septic shock. This system supports dynamic assessment and guides clinical intervention in critically ill patients.
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