[Non-invasive regional and cardiac output determination in healthy volunteers. Predictive value]

The effects of nifedipine (20 mg), propranolol (80 mg), the nifedipine (20 mg) + propranolol (80 mg) combination and a placebo on cardiac [heart rate (HR), cardiac output (CO, Doppler determination)] and systemic [mean arterial pressure (MAP), systemic vascular resistance (SVR)] and regional hemodynamic [brachial blood flow (BBF) and arterial diameter (BAD) (pulsed Doppler), forearm vascular resistance (FVR)] parameters were investigated during the 3 hours following their random administration in a double blind and cross over study performed in 6 healthy subjects. At their peak effects, (a) nifedipine decreased SVR (-17 p. 100, p less than 0.01), increased HR (+ 12p. 100, p less than 0.001) and CO (+ 18 p. 100, p less than 0.001), did not change MAP and increased BBF (+31 p. 100, p less than 0.001) with a vasodilating effect which affected both large and small arteries; (b) propranolol decreased HR (-14 p. 100, p less than 0.05) and CO (-25 p. 100, p less than 0.01), increased SVR (+25 p. 100, p less than 0.01), did not change MAP and decreased BBF (-28 p. 100, p less than 0.05) with a vasoconstrictor effect which affected both large and small arteries; (c) in the nifedipine-propranolol combination, nifedipine neutralized propranolol-induced systemic and regional vasoconstrictor effects while propranolol antagonized nifedipine-induced increases in HR and CO. Thus, the favorable synergistic effects of the nifedipine-propranolol combination in hypertensive patients could be demonstrated in healthy subjects inasmuch as MAP was decreased and peripheral vascular blood flows were preserved.(ABSTRACT TRUNCATED AT 250 WORDS)