Vasopressor Agents in Shock

Abstract

Critical hemodynamic changes that are observed with the reduction of blood pressure in shock and the use of vasopressor agents as a temporary measure for maintaining arterial pressure so that irreparable tissue damage can be prevented are considered in this review of the use and efficacy of vasopressor agents in shock. Indications for adrenergic stimulators include severe hypotensive episodes, in which case an alpha-beta stimulator such as metaraminol or norepinephrine is the therapy of choice; hemorrhagic shock, in which administration of an alpha-beta stimulator will help maintain essential cerebral and cardiac function by shunting blood to these areas while volume is being replaced; cardiogenic shock, in which vasodilators may reduce cardiac work by reducing diastolic blood pressure but coronary blood flow will also be reduced, counteracting the effects of decreasing the cardiac load; and endotoxic shock, in which the circulating blood volume decreases and venous return and cardiac output also decrease. Prolonged use of these agents in any of these shock situations is ultimately deleterious. Vasopressor drugs are best used to treat acute hypotension that occurs in myocardial infarction; in such cses, vasopressors are used to keep the blood pressure within normal range, but only as adjunctive therapy. In hemorrhagic shock, though norepinephrine administration may increase blood pressure, the only lasting treatment is to replace the blood as rapidly as possible.