Metoprolol in Acute Respiratory Distress Syndrome (MAIDEN)

Inclusion Criteria: * Patients (≥18 years and \<80 years) with a clinical diagnosis of ARDS of any aetiology (pneumonia, including SARS-CoV-2, sepsis, pancreatitis, bronchospasm and trauma) admitted to the ICU. * Orotracheal intubation (OTI) and mechanical ventilation within 72 hours prior to randomisation. * Moderate-severe ARDS (PaO2/FiO2: ≤200 mmHg under standardised conditions (PEEP≥5 cm H2O). * Heart rate ≥ 60 bpm. * Invasive systolic blood pressure ≥ 110 mmHg. Exclusion Criteria: * Prolonged hospital admission prior to randomisation (i.e. ≥7 days at the time of randomisation). * Reduced left ventricular ejection fraction (LVEF \<50%). * Life expectancy due to other processes (cancer, degenerative diseases, etc.) of less than 6 months. * Right ventricular (RV) systolic dysfunction. * Concomitant acute heart failure (cardiac index ≤2.5 L/m2 or pulmonary capillary pressure ≥15 mmHg or clinical suspicion). * Second-degree atrioventricular (AV) block, 2:1 AV block, high-grade/advanced AV block and third-degree AV block. Also significant sinus bradycardia, which would be implied by having a heart rate \>60 bpm as an inclusion criterion. * Pregnant or breastfeeding women. * Cardiogenic shock. * Persistent invasive blood pressure \<110 mmHg despite vasopressor agents. * Use of noradrenaline at concentrations greater than 0.2 µg/kg/min at the time of the randomisation. * Use of dobutamine within 48 hours before randomisation. * Concomitant pulmonary embolism. * Known severe peripheral arterial disease. * Known asthma before admission (with active bronchodilator therapy). * Active beta-blocker treatment prior to admission (i.e. within 3 months prior to admission).