Cardiovascular responsiveness to norepinephrine in mild essential hypertension

The responses of blood pressure, heart rate and forearm vascular resistance to exogenous norepinephrine (NE) were measured in 40 normotensive and 65 mildly hypertensive subjects (mean blood pressure 117/72 and 146/92 mm Hg, respectively). Both groups received low incremental doses of NE: 15, 30 and 60 ng/kg/min for 8 minutes each. In contrast to previous studies that compared the dose-response curves in normo- and hypertensive subjects, this study corrected the cardiovascular responses for the increment of plasma NE to account for differences in metabolic clearance of NE. Although age and sex appeared to play a role, the corrected cardiovascular responses did not differ significantly between normo- and hypertensive subjects. Thus, an increased cardiovascular sensitivity to exogenous NE was not demonstrated in mildly hypertensive subjects. This finding confirms some but not all previous studies of the dose-response relation.