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Author: Admin | 2025-04-28
Dobutamine is titrated to improve cardiac output, dose changes are typically made in collaboration with the prescriber.10Table: Vasoactive agents4,5Epinephrine A potent positive inotropic and chronotropic agent, epinephrine has a strong affinity for beta-1 receptors. Additionally, epinephrine increases blood flow to skeletal muscle beds and causes bronchodilation due to strong beta-2 properties. At higher doses, intense vasoconstriction occurs with administration of epinephrine due to stimulation of alpha-1 receptors. Epinephrine is indicated for cardiogenic and distributive shock, anaphylaxis, and acute, severe asthma unresponsive to other medications. Adverse reactions include tachycardia, dysrhythmias, myocardial ischemia, and poor peripheral perfusion. Epinephrine is a stress hormone that stimulates gluconeogenesis and insulin resistance, resulting in hyperglycemia. Because of potent adverse reactions, epinephrine is reserved for use as a second-line agent when other medications have not produced desired outcomes. Isoproterenol Isoproterenol is a beta-agonist medication with positive chronotropic and dromotropic activity. Vasoconstriction does not occur because isoproterenol lacks alpha-agonist properties. Therefore, isoproterenol causes a marked increase in heart rate and is used as a temporizing measure for symptomatic bradycardia.4 Although isoproterenol has some positive inotropic activity, the increase in cardiac output is attenuated by a reduction in afterload. A marked increase in heart rate makes isoproterenol an unsuitable choice for cardiogenic shock. Adverse reactions include tachycardia, myocardial ischemia, and ventricular dysrhythmias.Figure: Catecholamine medications6Norepinephrine A catecholamine agent with potent alpha-1 and mild beta-1 properties, norepinephrine has no beta-2 activity so the vasoconstrictive effects are unopposed. Consequently, norepinephrine is a potent vasopressor and weak positive inotrope. Norepinephrine is indicated for hypotension due to distributive shock states including septic and neurogenic shock.10 Adverse reactions include tachycardia, hypertension, ventricular dysrhythmias, and myocardial ischemia. Because of strong vasoconstrictive effects, high doses of norepinephrine can impede tissue perfusion, particularly of the skin, viscera, and kidneys. Phenylephrine A pure alpha-1 agonist, phenylephrine increases BP by causing vasoconstriction. Due to the lack of beta-agonist activity, phenylephrine has no direct effect on the myocardium. Therefore, phenylephrine is used to treat vasodilatory shock, particularly in patients at risk for developing tachydysrhythmias.10 Indications for phenylephrine include hypotension resulting from anesthesia, neurogenic shock, and vasoplegia after cardiopulmonary bypass. Increased left
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