Inotropic agents. Catecholamines, digoxin, amrinone

Three broad categories of pharmacologic support that enhance myocardial contractility and modify organ blood flow are reviewed. Appropriate selection among these compounds will minimize the occurrence of adverse effects. The catecholamines increase cardiac work and myocardial oxygen demand. In the setting of a failing ventricle, the increase in oxygen requirement may be balanced by improved coronary blood flow. Problems associated with catecholamines include tachycardia, induction of dysrhythmias, and unsuitable vasoconstriction. Epinephrine and isoproterenol are most likely to increase heart rate excessively. Norepinephrine is most likely to be associated with poor tissue perfusion. Amrinone, a bipyridine, has a favorable effect on oxygen balance in the failing ventricle and is unlikely to produce tachycardia or dysrhythmias. Principal concerns are the potential for accumulation in the patient with multiple organ system failure and the lack of pharmacokinetic information in critically ill patients, including children. Thrombocytopenia may be a problem as well. Digitalis glycosides are venerable drugs. Acute and chronic toxicity are problems that the intensivist is called on to treat frequently. Therapy with digitalis Fab fragments is now routine for severe intoxications and should improve outcome.