ObjectiveTo review the physiologic and pathophysiologic hyperadrenergic states and the pharmacologic use of sympathomimetic agents.Data SourcesPharmacologic and physiologic studies in experimental animals and humans.Data Extraction/SynthesisPlasma cat-echolamines are increased in a variety of clinical situations. Following major injury, cat-echolamines act to support vital organ perfusion and mobilize fuel substrates. However, with surgical trauma and during acute medical illnesses, such as myocardial infarction, cat-echolamine-induced physiologic changes can interact with underlying disease processes to result in clinically significant complications. Exogenous catecholamines are used to treat a variety of medical conditions, including ana-phylaxis and various shock states. Available sympathomimetic agents differ in their availability to stimulate different subpopulations of adrenergic receptors. These differences permit the astute clinician to achieve specific physiologic end-points. Finally, plasma catecholamines are increased in patients with pheochromocytoma. This latter condition provides insights into the long-term effects of cat-echolamine excess.ConclusionsBased on knowledge of the pharmacology of sympathomimetic agents and the physiologic consequences of adrenergic receptor stimulation, it is possible to prevent undesirable catecholamine effects and to utilize these agents to achieve desired therapeutic goals. (Crit Care Med 1991; 19:1566)