Esmolol is also called esmolol hydrochloride. This drug is mainly used in tachycardia or hypertension due to the surgical period, sinus tachycardia, supraventricular tachycardia requiring emergency management, and sinus node impulse formation at a rate of more than one hundred beats per minute in adults. Also, it is useful for fever, hypotension, hypoxia, cardiac insufficiency, anemia, etc. So the drug action is relatively broad and it is actually a selective beta1 receptor blocker. The dosage varies, depending on the situation, if it is applied before tracheal intubation, it is usually 1mg/kg-2mg/kg. in the perioperative period, its loading dose is 0.25mg/kg-0.5mg/kg intravenous push, four minutes of maintenance. The main adverse effects are hypotension and bradycardia, so this drug has a more pronounced effect.