Intravenous hexamethonium sensitivity and responses to oral treatment.

This study represents an effort to distinguish between neurogenic and humoral vasoconstrictive factors in a representative group of hypertensive patients by the response to hexamethonium ganglionic blockade. The correlation between intravenous hexamethonium sensitivity and subsequent treatment response was also determined. O~NE of the most difficult problems in essential hypertension is to select the treatment most apt to benefit the individual patient. Many present-day therapies are believed to act by blocking or depressing some part of the nervous system in the patient with excessive neurogenic vasoconstriction. The effects of cold,' sleep and barbiturate ad-ministration2 and spinal anesthesiaa have been used to select this type of patient for treatment. None of these measures has been conspicuously successful,4 perhaps because their action is not confined to the neurogenic pressor mechanism or, conversely, is incomplete. The effect of hexamethonium chloride appears to be limited to a temporary blockade of sympathetic and parasympathetic ganglia.5 The drug can be given intravenously at any desired concentration and rate. For these reasons, we have used an intravenous hexa-methonium test to determine whether patients with excessive neurogenic vasoconstriction could be singled out by their response to auto-nomic blockade; and, as a corollary, whether the existence of significant non-neurogenic vasoconstriction could be demonstrated by the failure of the blood pressure to fall materially after maximum tolerated doses of hexamethonium. We have also attempted to determine whether the results of oral hexa-methonium treatment could be anticipated from the intravenous response. The subjects were 23 patients with essential hypertension, ranging in age from 26 to 72 years. None showed evidences of coronary insufficiency or congestive failure at the time of study. The known duration of the disease ranged from 6 months to 30 years. The status of each patient was evaluated by a complete history and physical examination, x-ray study for heart size, electrocardiogram, urinary concentration test and blood nonprotein nitrogen determination. Funduscopic findings, heart size, and electrocardiographic patterns were graded from 1 to 4. The results of these evaluations indicated that the subject group represented a wide range of hypertensive disease (table 1). The intravenous hexamethonium test was performed as follows: The height and weight were measured and the surface area calculated. The blood pressure was then determined with a mercury sphygmomanometer at one-to two-minute intervals with the patient sitting. After the pressure had stabilized, a 2 per cent solution of hexamethonium chloride was injected into an antecubital vein.* The drug …