HEMODYNAMIC EFFECTS OF ACUTE AND PROLONGED β-ADRENERGIC BLOCKADE IN ESSENTIAL HYPERTENSION

Absrract. Hemodynamic studies have been performed in 15 male patients with mild to moderately severe essential hypertension. Studies were made after four weeks of placebo treatment and again after acute i.v. administration of propranolol (0.22 mg/kg) and after four weeks of oral propranolol therapy (160-320 mg daily). After acute /3-adrenergic blockade a significant reduction of cardiac index (Qi) occurred, while total peripheral resistance (TPR) increased significantly, resulting in unaltered BP. After four weeks of oral propranolol the Qi remained significantly reduced, but TPR was readjusted towards the initial level, resulting in a reduction of BP in most patients. Major reductions of stimulated plasma renin activity were seen, but these were not correlated to the changes of BP, Qi or TPR. Studies of the baroreceptor reflex by means of i.v. administration of angiotensin suggested a change towards increased sensitivity, although this change did not achieve statistical significance.