The effects of intravenous guanethidine on the systemic and pulmonary circulations in man

Abstract

The effects of the intravenous injection of guanethidine on the systemic and pulmonary circulations have been studied in 4 normal subjects and 12 hypertensive patients at rest and during graded leg exercise in the supine position. The drug caused a fall in the resting systemic arterial blood pressure and systemic vascular resistance in all subjects; there was a marked quantitative difference in the response of the normal subjects as compared to that of the hypertensive patients, the latter patients exhibiting much greater falls in blood pressure and systemic vascular resistance after a given dose of the drug. Supine leg exercise was not associated with any further fall in systemic blood pressure. Neither the resting nor the exercising cardiac outputs were affected by the drug in either normal or hypertensive subjects. Although the resting heart rate was unchanged after the drug, there was a relative bradycardia during exercise in both the normal subjects and hypertensive patients after the drug, as compared to the control study. There was a small but definite reduction in the pulmonary vascular resistance without change in the pulmonary wedged pressure in both normal subjects and hypertensive patients. These findings are discussed particularly in comparison with the circulatory effects of bretylium tosylate studied under similar conditions.