Though the pulmonary blood vessels appear to be abundantly supplied with autonomic neurones from both the sympathetic and parasympathetic nervous systems, the functional activities of these fibres in man continue to elude precise definition. Equally obscure is the part played in the maintenance of normal pulmonary vascular tone by the endogenous circulating catecholamines.In this latter respect, previously reported studies, which appear to have been entirely concerned with the effects of adrenergic blocking agents in patients suffering from severe pulmonary vascular diseases, have yielded largely irreconcilable results. Further, there appear to be no reports of the effect of these drugs on the systemic venous pressure of man. The present report, part of a larger study of the over-all circulatory effects of one of these agents, phentolamine, concerns an analysis of the effects of this drug on the pulmonary and venous circulations of normal subjects and of patients suffering from hypertensive vascular disease.
SUBJECTS AND METHODSClinical Data. Studies were made on 6 normal subjects and 6 hypertensive patients; details of each are listed in Table I.All the hypertensive patients were considered to be suffering from essential hypertension on the basis of the usual diagnostic clinical criteria. None had any symptoms referable to the cardiovascular system except patient A.A., who had mild exertional dyspncra. In 5 of the 6 patients the resting diastolic pressure, recorded in the supine position, exceeded 120 mm. Hg. In 4 of the hypertensive patients (E.B., J.W., J.N., and F.E.) there was no radiological or electrocardiographic evidence of left ventricular enlargement. In the remaining 2 patients there was radiological evidence of cardiac hypertrophy without dilatation and in both instances this was associated with electrocardiographic changes indicative of moderate left ventricular hypertrophy. The optic fundi were without papilloedema, hkmorrhages, or exudates in all 6 hypertensive patients; routine tests of renal function were also within normal limits and arteriographs showed no evidence of renal vascular disease. The 24-hour urinary excretion of vanillylmandelic acid was within normal limits in all the hypertensive patients.Plan of Investigation. The investigation was designed to study the changes occurring in the pulmonary circulation following the abrupt intravenous injection of phentolamine in the dose usually used in clinical diagnostic procedures. In all individuals pulmonary arterial and wedge pressures, systemic arterial and right atrial pressures, cardiac output, and heart rate were measured during a control period of 10 minutes and then for a further 30 minutes following the rapid intravenous injection of 5 mg. phentolamine in a volume of 2 ml.; the injection was completed within two seconds.All vascular pressures and heart rate were recorded continuously throughout the study. Cardiac output was determined on alternate minutes during the control period, every minute for the 6 minutes after injection of th...