Tachycardia often presents difficult management problems in anesthesia. Because it increases myocardial oxygen demand so sharply, tachycardia can quickly place patients at risk of myocardial ischemia. It can occur for any number of reasons. Deepening the anesthetic, either with inhalation agent or opioids, will ablate increases in heart rate, but changes in heart rate are often transient and changes in anesthetic depth are often not. Esmolol (Brevibloc) is a unique, short-acting beta blocker that is strongly beta 1 selective at usual clinical doses. As with other beta blockers, esmolol becomes less selective for the beta 1 receptor as its dose is increased. It is metabolized by red blood cell esterases resulting in a half-life of 9 minutes. Fifteen minutes after a bolus dose, esmolol is difficult to detect in the plasma. Its metabolites have clinically undetectable activity and are eliminated renally. Esmolol may be administered by intermittent, intravenous bolus doses or by continuous infusion. Infusions should be preceded by loading doses. Dose range varies with the patient's status, clinical situation, concomitant medications, and desired result. Patients receiving esmolol should be monitored because of its bradycardic and hypotensive effects.