Acute respiratory distress syndrome (ARDS) is a clinical syndrome caused by intrapulmonary and/or extrapulmonary causes, characterized by intractable hypoxemia. Studies have shown that the sympathetic nervous system is over-activated in patients with acute respiratory distress syndrome. A large retrospective study showed a reduction in mortality in ARDS patients treated with oral β1 blockers before admission, and this beneficial effect of β1 blockers applies to ARDS patients with or without cardiac disease. Esmolol is an ultra-short-acting selective β1 receptor blocker. Previous studies have shown that esmolol can improve oxygenation and reduce the levels of inflammatory cytokines and exudate proteins in bronchoalveolar lavage fluid, thereby alleviating pulmonary injury. According to the literature and our previous clinical observations, we made the following hypothesis: When Estolol is applied to various ARDS patients undergoing mechanical ventilation in ICU, it can control the heart rate by inhibiting β-adrenergic receptor, which can ultimately improve the oxygenation index of patients and shorten the mechanical ventilation time. This project intends to include ARDS patients with optimal hemodynamic treatment for 24 hours, whose heart rate is still ≥95 beats/min after conventional treatment, but ≤120 beats/min. They are randomly divided into control group and Esmolol treatment group to study the effects of esmolol on patients' oxygenation index, mechanical ventilation time, hemodynamics, function of various organs and inflammation level. The aim of this study is to optimize the treatment of ARDS patients.

At present, there are few studies on Esmolol in acute respiratory distress syndrome. However, previous studies have shown that Esmolol can improve oxygenation and reduce the levels of inflammatory cytokines and exudate proteins in bronchoalveolar lavage fluid, thus alleviating pulmonary injury. Considering that a considerable number of ARDS patients in the intensive care unit suffer from sepsis, we conducted this study to explore the application timing of esmolol therapy and whether esmolol can improve the symptoms and prognosis of ARDS patients. Based on the literature and our previous clinical observations, we make the following assumptions: Esmolol is applied to various ARDS patients receiving mechanical ventilation in ICU. By inhibiting the β-adrenergic receptor to control the heart rate, it can ultimately improve the oxygenation index of patients, shorten the mechanical ventilation time, achieve tracheal intubation extraction as soon as possible, and reduce the 28-day mortality. At the same time, esmolol can also improve the function of various organs of patients and reduce the level of inflammatory factors. This project intends to include ARDS patients with optimal hemodynamic treatment for 24 hours, whose heart rate is still ≥95 beats/min after conventional treatment, but ≤120 beats/min. They are randomly divided into control group and Esmolol treatment group to study the effects of esmolol on patients' oxygenation index, mechanical ventilation time, hemodynamics, function of various organs and inflammation level. To optimize the treatment of ARDS patients.

Acute respiratory distress syndrome (ARDS) is a clinical syndrome caused by intrapulmonary and/or extrapulmonary causes, characterized by intractable hypoxemia. ARDS is the most common cause of respiratory failure in severe patients, and also the main factor leading to poor prognosis in severe patients. In recent years, although the research on ARDS has continued to go deeper, clinical treatment still remains in the stage of lung protective ventilation and restricted fluid management, and there is still a lack of specific drug therapy, and the fatality rate is still as high as 40%.

Studies have shown that the sympathetic nervous system is over-activated in patients with acute respiratory distress syndrome. Because 75 to 80 percent of myocardial adrenergic receptors are β1 type, and adrenergic stress is primarily mediated by beta receptors, the heart is a prime target for sympathetic overstimulation. Elevated heart rate is associated with adverse outcomes in patients with severe infection and represents the severity of the disease.Another large retrospective study showed a reduction in mortality in ARDS patients treated with oral β1 blockers before admission, and this beneficial effect of β1 blockers applies to ARDS patients with or without cardiac disease.

Esmolol is an ultra-short-acting selective β1 receptor blocker, which mainly inhibits β1 receptor by competing for catecholamine binding sites in myocaroma, and has the effect of slowing resting and exercise heart rate, lowering blood pressure, and reducing myocardial oxygen consumption. Esmolol is a metabolite coupled with enzyme, so its distribution half-life is very short, intravenous injection begins to take effect 1-2 min, elimination half-life is only 9min, easy to control, high safety, and remarkable effect. There have been numerous studies on esmolol in sepsis. For patients with septic shock, the use of esmolol can reduce heart rate to the target level, but does not increase the incidence of adverse events, and does not reduce microcirculation perfusion, and can improve the hemodynamics and 28-day mortality of patients. In addition, both animal and human experiments have proved that Esmolol can reduce the release of inflammatory factors in sepsis, improve inflammatory response, and protect cardiac and renal function.

At present, there are few studies on Esmolol in acute respiratory distress syndrome. However, previous studies have shown that Esmolol can improve oxygenation and reduce the levels of inflammatory cytokines and exudate proteins in bronchoalveolar lavage fluid, thus alleviating pulmonary injury. Considering that a considerable number of ARDS patients in the intensive care unit suffer from sepsis, we conducted this study to explore the application timing of esmolol therapy and whether esmolol can improve the symptoms and prognosis of ARDS patients. Based on the literature and our previous clinical observations, we make the following assumptions: Esmolol is applied to various ARDS patients receiving mechanical ventilation in ICU. By inhibiting the β-adrenergic receptor to control the heart rate, it can ultimately improve the oxygenation index of patients, shorten the mechanical ventilation time, achieve tracheal intubation extraction as soon as possible, and reduce the 28-day mortality. At the same time, esmolol can also improve the function of various organs of patients and reduce the level of inflammatory factors. This project intends to include ARDS patients with optimal hemodynamic treatment for 24 hours, whose heart rate is still ≥95 beats/min after conventional treatment, but ≤120 beats/min. They are randomly divided into control group and Esmolol treatment group to study the effects of esmolol on patients' oxygenation index, mechanical ventilation time, hemodynamics, function of various organs and inflammation level. To optimize the treatment of ARDS patients.

To evaluate the effect of Esmolol control on heart rate in patients with acute respiratory distress syndrome (ARDS) on oxygenation index. A total of 187 patients aged 18-65 years who met the 2012 Berlin diagnostic criteria for acute respiratory distress syndrome will be included in our study. Hemodynamic optimization was performed within 24 hours after diagnosis. After treatment, the patient's heart rate continued to be ≥95 beats/min but ≤120 beats/min for at least 10 minutes, with or without esmolol pumping. The improvement of oxygenation index in different treatment groups was observed.

Inclusion Criteria:

• Meeting the 2012 Berlin diagnostic criteria for acute respiratory distress syndrome;
• Aged between 18-65 years (inclusive);
• 95 times/min ≤ heart rate ≤120 times/min;
• The patient needs to undergo endotracheal intubation mechanical ventilation after condition assessment;
• Obtain the informed consent of the patient or his legal representative.

Exclusion Criteria:

• Bradycardia and second degree or more atrioventricular block;
• Long-term use of beta-blockers;
• Combined with emphysema, asthma and other β-blocker contraindicated diseases;
• Cardiac insufficiency (NYHA grade Ⅲ or Ⅳ);
• Pregnancy