Remifentanil Versus Dexmedetomidine for Post-Cardiac Surgery Patients With Noninvasive Ventilation Intolerance: A Prospective, Observational,Cohort Study

This study is a prospective,observational,cohort study. Data of post-cardiac surgical patients who receives noninvasive ventilation (NIV) in the investigators' cardiac surgical intensive care unit are prospectively collected into a database for further analyzation since January 2018. Tolerance of NIV is estimated by a four-point NIV intolerance score system: A score of 1 indicates a comfortable and relaxed patient tolerating NIV; a score of 2 indicates mild intolerance with some discomfort and occasional grabbing at the NIV mask; a score of 3 indicates moderate intolerance and discomfort with the NIV mask most of the time with frequent grabbing at the mask (sometimes pulling it off); and a score of 4 indicates severe NIV intolerance with agitation or/and an inability to leave the NIV mask in place. Participants who receives re-intubation will be recorded as 4 points. Application of remifentanil or dexmedetomidine will be initiated when a score of 3 or 4 was recorded, according to the intensivists' preference.Depending on the sedation regime applied, patients with NIV intolerance are divided into two groups: remifentanil group and dexmedetomidine group.The investigators will compare the two groups with the NIV intolerance score at 15min,1, 3, 6, 12, 24, 48, 60 and 72 hours after the initiation of the sedation regime. The investigators will also compare the two groups with clinical outcomes such as NIV failure, tracheotomy rate, mortality, ICU length of stay etc.