Digital vascular reactivity to L-norepinephrine in the second trimester of pregnancy as a test for latent essential hypertension and toxemia

Abstract

I N 1 9 5 7 1 neurogenic vasoconstriction was estimated quantitatively by measuring blood pressure and blood flow in the digit under standardized conditions of rest and room temperature and again after vasodilatation by indirect heat supplemented by the intravenous injection of a ganglion-blocking drug. These data were converted to radius equivalents by means of PoiseuiIle's law ancl from these radius equivalents and the pressures the physical work performed by the smooth muscle of the blood vessels in changing one steady state (vasodilatation) to another (vasoconstriction) was calculated. With these methods, neurogenic vasoconstriction was demonstrated to be increased over normal values in essential hypertension. A similar procedure was subsequently applied to estimating vascular reactivity to L-norepinephrine (NE) by measuring the work of vasoconstriction produced by digital vascular smooth muscle in response to a fixed rate of infusion of NE.2 Such reactivity was found to be strikingly and uniformly increased in essential hypertension.