Effect of low-dose epinephrine infusion on hemodynamics after selective and nonselective β-blockade in hypertension

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Abstract
Hemodynamic effects of low doses of epinephrine were studied in 5 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 .mu.g/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. Evidently, infusion of small doses of epinephrine results in a marked difference in reaction in propranolol- and metoprolol-treated patients. This may have relevance in the choice of .beta.-blocker used in the treatment of hypertension.