Clinical pharmacology of alpha2-agonist and beta-adrenergic blocker

The pharmacological properties of centrally acting alpha2-receptor agonists such as clonidine suggest a potentially important role as ideal adjuvants for anesthesia since they produce sedation, analgesia anxiolysis, xerostomia and cardiovascular stability without respiratory depression, development of tolerance or addiction liability. Further clinical experience with this exciting development will undoubtedly establish the ultimate role and optimal use of alpha2 -receptor agonists in anesthetic practice. Beta-blockage can result in significant bradycardia, atrial ventricular conduction problems, bronchospasm and left ventricular contractile dysfunction. Thus, the use of long-acting beta-blockers is of limited value in the perioperative period. Esmolol, because of its ultrashort action, cardioselective properties and titratability, has been shown to be safe and effective for the treatment of tachycardia and hypertension. Doses from 50 to 300 micrograms/kg/min for up to 7 hours in the perioperative period have been shown to cause no apparent cumulative effect. It has been used in the treatment of asthmatic patients with tachycardia and hypertension without significant increases in airway resistance. Studies using esmolol during general anesthesia have demonstrated no significant interaction with several anesthetic regimens.