Inclusion Criteria:  Patients age ≥18 years confirmed to have COVID-19 pneumonia by nasopharyngeal swab PCR together with chest radiology requiring invasive mechanical ventilation.  Exclusion Criteria:  heart rate <50 beats per minute, atrioventricular conduction block of grade II or III, mean arterial pressure (MAP) <55 mmHg (despite appropriate intravenous volume replacement and vasopressor treatment), acute severe neurological disorder, propofol or dexmedetomidine allergy or other contraindications.