Esmolol hydrochloride is primarily used in medical settings as a short-acting beta-blocker. It is administered intravenously to manage rapid heart rates, particularly in situations like atrial fibrillation or atrial flutter, where controlling the heart rate is critical. It is also utilized during surgical procedures to prevent or treat tachycardia and hypertension, ensuring stable cardiovascular conditions. Due to its rapid onset and short duration of action, it is ideal for acute scenarios, allowing precise control and quick adjustments as needed. Additionally, it is sometimes used in emergency settings to manage hypertensive crises or to stabilize patients with severe heart conditions. Its effectiveness and safety profile make it a valuable tool in critical care and anesthesiology.