Work of Digital Vasoconstriction Produced by Infused Norepinephrine in Primary Hypertension

After prior sympathetic nerve inhibition by indirect heat and ganglion blockade, the sensitivity of the digital blood vessels to infused norepinephrine was measured from the work of digital vasoconstriction per milligram of norepinephrine infused per minute. The results in 15 patients with primary hypertension were compared with those in 15 normotensive subjects. Sensitivity to norepinephrine was uniformly increased in the hypertensive group. This could be attributed to a chemical change in vascular smooth muscle, such as a deficit in the enzyme responsible for norepinephrine degradation, to hypertrophy of this smooth muscle, or to both factors. The procedure may be useful for the detection of early or masked primary hypertension.