The hemodynamic effects in normal man of the subcutaneous administration of 0.5 mg and 0.25 mg of epinephrine, an agent which stimulates α adrenergic and β adrenergic receptors, and of 0.5 mg and 0.25 mg of terbutaline, an agent with a more selective β2 adrenergic activity in isolated organ preparations, and normal saline were assessed by a double blind study using a modified Latin square design. Noninvasive circulatory techniques were employed because of the large number of measurements and the 5 hr duration of study for each agent. Instantaneous pulmonary capillary blood flow and calf blood flow were measured. Ten normal volunteers were studied in the supine position on alternate days. After a control period of 1 hr, the hemodynamic effects of these agents were studied over a 4 hr period. Epinephrine and terbutaline had qualitatively similar actions. In terms of quantitative hemodynamic effects, 0.25 mg of terbutaline sulfate was equivalent to 0.5 mg of epinephrine hydrochloride. Terbutaline initially appeared to stimulate both β1 adrenergic and β2 adrenergic receptors, as evidenced by tachycardia, increased stroke volume associated with a fall in systemic vascular resistance, and an increase in calf blood flow. One to 4 hr after injection, the fall in systemic vascular resistance persisted, accompanied by an increased cardiac output related solely to tachycardia, since stroke volume had reached baseline values. Indirect evidence suggested that both terbutaline and epinephrine might have produced pulmonary vasodilatation; terbutaline appeared to give a longer duration of action.
ASJC Scopus subject areas
- Pulmonary and Respiratory Medicine
- Critical Care and Intensive Care Medicine
- Cardiology and Cardiovascular Medicine