Effect of low-dose epinephrine infusion on hemodynamics after selective and nonselective beta-blockade in...

We studied hemodynamic effects of low doses of epinephrine in five hypertensive patients receiving long-term treatment with propranolol and metoprolol. Epinephrine was infused at graded rates of 0.5, 1.0, 2.0, and 4.0 micrograms/min. During propranolol treatment epinephrine induced a marked pressor effect at all rates. There was a considerable rise in systolic as well as in diastolic blood pressure and heart rate fell. During metoprolol treatment there was only a slight rise in blood pressure and heart rate rose. Forearm blood flow was decreased by epinephrine during propranolol. Calculated forearm vascular resistance showed opposite effects. We conclude that infusion of small doses of epinephrine results in a marked difference in reaction in propranolol- and metoprolol-treated patients and that this may have relevance in the choice of beta blocker to be used in the treatment of hypertension.