The Reaction of the Capillary Bed of the Nailfold to the Continuous Intravenous Infusion of Levo-Nor-Epinephrine in Patients With Normal Blood Pressure and With Essential Hypertension

The intravenous infusion of l-nor-epinephrine in persons with normal cardiovascular systems produces a hemodynamic state which in many respects resembles that found in patients with essential hypertension. In the systemic circulation there is in each of the two conditions an elevation of the systolic, diastolic and mean arterial pressures, an unchanged or moderately decreased cardiac output, an increase in systemic peripheral resistance and usually an absence of subjective symptoms (1). This similarity in the two hemodynamic states has led to the suggestion that l-nor-epinephrine may be a humoral agent responsible for essential hypertension. If this were true, then the hypertensive state produced by l-nor-epinephrine should produce changes in all portions of the circulatory system similar to those found in essential hypertension. The dynamics of the pulmonary circulation have been shown to be different in the two states; the intravenous infusion of l-nor-epinephrine raises mean pulmonary arterial pressure whereas this pressure is normal in patients with uncomplicated essential hypertension (1). The present study was undertaken to determine whether the circulation in specific portions of the systemic vascular system, in this instance the peripheral cutaneous capillaries, is the same in subjects with l-nor-epinephrine induced hypertension as in patients with essential hypertension. Accordingly, the capillary circulation of the nailfold during the sustained hypertensive state induced in control subjects by continuous intravenous infusion of l-nor-epinephrine was compared with the nailfold capillary circulation of patients with essential hypertension. The observations indicate that for similar levels of elevated arterial pressure the capillary circulation of the nailfold is more reactive in the l-nor-epinephrine induced hypertension than in essential hypertension. A previous study indicated that the nailfold capillary circulation of subjects with essential hypertension was more reactive to single rapid injections of epinephrine than the similar capillary circulation of control subjects (2). The present study extends this observation to indicate that such hyper-reactivity persists over the several hours of a continuous infusion of l-nor-epinephrine.