[Beta blockers and anesthesia]

Abstract

Beta-adrenoceptor antagonists (BB) demonstrate a competitive antagonism with endogenous catecholamines. Beta-1 receptor blockade mediates the depressive action on contractility, heart rate and atrio-ventricular conduction. Beta-2 receptor blockade mediates vascular, bronchial and uterine smooth muscle constriction. BB with beta-1 selective and intrinsec sympathomimetic activity do not increase systemic vascular resistance. BB are mostly used to treat ischaemic heart disease, hypertension and arrhythmias. Bradycardia, hypotension and bronchospasm are the main hazards in BB treated patients undergoing anaesthesia. However giving BB with premedication to patients taking usely this treatment allows better perioperative haemodynamic stability and avoids rebound effect. Experimentally, oxprenolol reverses regional dysfunction in ischaemic myocardium under halothane anaesthesia. During and after anaesthesia, intravenous (i.v.) BB must be used with caution to treat hypertension associated with tachycardia. In controlled hypotension, i.v. BB potentialise other agents. In phaechromocytoma surgery, alpha-blocking drugs are essential but additional BB can control tachycardia successfully. In coronary artery bypass surgery, giving BB prior to induction decreases cardiac enzymes serum levels. Esmolol, a new ultra-short-acting BB, would control perioperative tachycardia and hypertension without risk of prolonged cardiac depression.