Hemodynamic Spectrum of Vasopressor and Vasodilator Drugs

Hemodynamic effects of vasopressor agents and vasodilator drugs were compared in order to clarify differences which would be of practical significance for their use in treatment of circulatory shock. The alpha-adrenergic agents, methoxamine and phenylephrine hydrochloride, increased arterial pressure and decreased heart rate and venous return. The beta-adrenergic agents, mephentermine and isoproterenol hydrochloride, and the alphaadrenergic blocking agents, phentolamine mesylate and phenoxybenzamine hydrochloride, produced similar hemodynamic effects. Both groups of drugs increased heart rate and venous return. An intermediate response was observed with epinephrine, levarterenol bitartrate, and metaraminol bitartrate, drugs which have both alphaand beta-adrenergic actions. In these studies, the limited significance of a classification which is based on the pressor response became apparent. When the effects are viewed as a spectrum of hemodynamic actions, the apparent paradox between vasopressor and vasodilator therapy for shock is largely resolved.