Corticosteroids in Hyperinflammatory Phenotype of Critical Illness

Inclusion Criteria: Participants must meet all of the following criteria: 1. Age ≥18 years. 2. Diagnosis of acute respiratory distress syndrome (ARDS) or sepsis. ARDS will be defined according to standard criteria: 1. acute onset within 1 week of a known clinical insult or new/worsening respiratory symptoms; 2. bilateral pulmonary opacities on chest imaging (X-ray or CT) or bilateral B-lines and/or consolidation on lung ultrasound, not fully explained by effusion, atelectasis, or nodules; 3. respiratory failure not fully explained by cardiac failure or fluid overload; 4. hypoxemia defined as PaO₂/FiO₂ ≤300 mmHg or SpO₂/FiO₂ ≤315 (with SpO₂ ≤97%) under a minimum positive end-expiratory pressure (PEEP) of 5 cmH₂O. Sepsis will be defined according to the Sepsis-3 criteria as suspected or confirmed infection with an acute increase in SOFA score ≥2 points, assuming a baseline SOFA score of 0 in patients without known prior organ dysfunction. Sepsis-associated ARDS will be defined as ARDS occurring in patients with sepsis. 3\. Receiving invasive mechanical ventilation. 4. Admission to the intensive care unit (ICU). 5. Hyperinflammatory phenotype, defined as a predicted probability ≥0.5 using a validated AI clinical classifier based on clinical data. 6\. Randomization within 72 hours of ARDS or sepsis onset. 7. Provision of written informed consent by the patient or their legally authorized representative. Exclusion Criteria: Participants meeting any of the following criteria will be excluded: 1. Requirement for high-dose vasopressor support, defined as norepinephrine ≥0.5 μg/kg/min or epinephrine ≥0.25 μg/kg/min. 2. Post-cardiac surgery patients (e.g., coronary artery bypass grafting or valve replacement). 3. Conditions requiring systemic corticosteroid therapy exceeding 1 mg/kg methylprednisolone or an equivalent dose (e.g., acute asthma exacerbation, acute exacerbation of chronic obstructive pulmonary disease, or autoimmune diseases). 4. Long-term systemic corticosteroid use within the past 6 months. 5. Pregnancy or lactation. 6. Brain death. 7. Advanced malignancy or other end-stage disease with an expected survival of less than 6 months, or anticipated death within 24 hours. 8. Known hypersensitivity to methylprednisolone, including but not limited to urticaria, eczema, angioedema, bronchospasm, or anaphylaxis. 9. History of solid organ transplantation or allogeneic hematopoietic stem cell transplantation. 10. Active life-threatening fungal infection or tuberculosis. 11. Neuromuscular disorders affecting spontaneous respiration. 12. Severe inherited or acquired immunodeficiency (e.g., human immunodeficiency virus infection, chronic granulomatous disease, or severe combined immunodeficiency). 13. Do-not-resuscitate (DNR) orders or withdrawal of life-sustaining treatment. 14. Concurrent participation in another interventional clinical trial. 15. Any other condition that, in the opinion of the treating physician or investigator, would make participation in the study inappropriate.