Short-term systemic hemodynamic adaptation to beta-adrenergic inhibition with atenolol in hypertensive patients. Hypertension 1981:3:262-268 12

SUMMARY Early systemic hemodynamic adjustments to antihypertensire therapy with the cardioselective beta inhibitor, atenolol, were investigated in 12 hospitalized men, mean age 52 years, with uncomplicated mild-to-moderate essential hypertension. Twice daily measurements of cardiac output (CO) by CO3 rebreathing, blood pressure by cuff, and heart rate were performed in all subjects for 3 days before and S days after initia-tion of oral atenolol therapy (50 or 100 mg daily). Cardiac output by CO, rebreathing was checked with dye diluion just before, and 4 hours and 4 days after the start of therapy. Plasma volume (radioiodinated albumin) was measured before therapy and on Day 5 of therapy. The CO results obtained with the two methods were not significantly different (r = 0.88,p < 0.01, n = 12). A reduction in heart rate, 18 ± 2 beats/min (mean ± SE), occurred in all patients while taking atenolol. By 4 hours after the first dose of atenolol, CO fell from 5.49 ± 030 to 4.24 ± 0.21 liters/min (p < 0.01), while the control mean arterial pressure (MAP) of 108 ± 4 mm Hg was not significantly changed, 110 ± 4 mm Hg. At 24 hours, CO returned near baseline (5.10 ± 0.21 liters/min) but MAP was reduced (95 ± 3 mm Hg, p < 0.001) and remained so thereafter. CO remained at baseline at 48 hours (5.50 ± 0.29 liters/min) but fell again (p < 0.01) to 4.81 ± 0.11 on Day 4 and to 4.68 ± 0.25 liters/min on Day 5 of atenolol therapy. Plasma volume, 3110 ± 100 ml before therapy, was reduced to 2850 ± 100 by Day 5 of atenolol therapy (p < 0.01). The findings indicate a delayed onset of th