title: Short-term systemic hemodynamic adaptation to beta-adrenergic inhibition with atenolol in hypertensive patients.
abstract: Early systemic hemodynamic adjustments to antihypertensive 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 CO2 rebreathing, blood pressure by cuff, and heart rate were performed in all subjects for 3 days before and 5 days after initiation of oral atenolol therapy (50 or 100 mg daily). Cardiac output by CO2 rebreathing was checked with dye dilution 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 less than 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 +/- 0./30 to 4.24 +/- 0.21 liters/min (p less than 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 less than 0.001) and remained so thereafter. CO remained at baseline at 48 hours (5.50 +/- 0.29 liters/min) but fell again (p less than 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 less than 0.01). The findings indicate a delayed onset of the antihypertensive action of atenolol. The transient return to baseline of CO on Day 2 and 3 of atenolol therapy suggests a reverse autoregulatory adjustment to the initial fall in CO.
mesh_terms: D000319:Adrenergic beta-Antagonists / Q000494:pharmacology / Q000627:therapeutic use*; D000328:Adult; D001262:Atenolol / Q000494:pharmacology / Q000627:therapeutic use*; D002302:Cardiac Output / Q000187:drug effects; D006339:Heart Rate / Q000187:drug effects; D006439:Hemodynamics / Q000187:drug effects*; D006706:Homeostasis; D006801:Humans; D006973:Hypertension / Q000188:drug therapy*; D008297:Male; D008875:Middle Aged; D010953:Plasma Volume / Q000187:drug effects; D011412:Propanolamines / Q000627:therapeutic use*; D012083:Renin / Q000097:blood; D014655:Vascular Resistance / Q000187:drug effects
chemical_list: D000319:Adrenergic beta-Antagonists; D011412:Propanolamines; D001262:Atenolol; D012083:Renin