Colistin Methanesulfonate Sodium Inhalation for Prophylaxis of Ventilator-Associated Pneumonia (CIVAP): A Prospective, Multicentre, Double-Blind, Randomized, Placebo-Controlled Trial

Participants will be enrolled if they meet the following criteria: 1. Age ≥18 years; 2. Mechanical ventilation for more than two consecutive days (48 hours); 3. Patient has high-risk factors for multidrug-resistant bacterial infections, which meet any of the following criteria: (1)History of antibiotic exposure within 30 days; (2)Hospitalization time\>5 days (120 hours); (3)Septic shock; (4) ARDS; (5)Accept renal replacement therapy; (6)Previous colonization of multidrug-resistant bacteria; 4. Informed consent of the patient or a proxy was written. Participants will be excluded in case of: 1. Suspected or confirmed VAP at the inclusion day; 2. Patient ventilated through an endotracheal tube for more than four consecutive days (96 hours); 3. Expected that endotracheal intubation will be removed within the next 24 hours; 4. Tracheostomy; 5. Allergy to CMS; 6. Patients has polymyxins medication history within 7 days or clinical indication for systemic CMS therapy at the inclusion day; 7. Chronic kidney failure with baseline glomerular filtration ≤30 mL/min or Stage 3 classification AKI (KDIGO) (excluding patients undergoing renal replacement therapy); 8. Expected survival time not exceeding 48 hours; 9. Pregnancy or breastfeeding period; 10. Patients previously included in this study or are using any inhaled antibiotics or are participating in other clinical studies within 30 days.