HEMODYNAMIC-STUDIES ON THE BLOOD PRESSURE-RAISING EFFECT OF MINERALOCORTICOIDS

The effects on systemic haemodynamics of long-term administration of high mineralocorticoid doses were studied in six healthy volunteers. The subjects received the synthetic steroid fludrocortisone in a daily oral dose of 0.8 mg. Central venous and arterial pressures were recorded directly, and cardiac output was determined by dye dilution method before as well as after 1 and 6 weeks of steroid application. Within the first week of steroid administration, mean arterial pressure rose by 5.6±4.6 (±S.D.) mm Hg (p<0.025). Body weight increased by 2.5±1.1 kg (p<0.01), and central venous pressure by 1.3±1.4 mm Hg (p<0.05). An increase in cardiac index was observed in all subjects, the average increase was 0.72±0.47 l/min·m2 (p<0.01). Heart rate decreased. After the 6th week of steroid administration, blood pressure had risen in all subjects, the average increase in mean arterial pressure was 17.8±6.0 mm Hg (p<0.001). This pressure rise was the consequence of an increase in total peripheral resistance by 267±125 dyn·cm-5·s (p<0.01) on the average. At that time cardiac index was even lower than at the first study in five of the six subjects. Compared to the second study, heart rate had decreased further, central venous pressure had increased further, and body weight had not changed significantly. The data show that the mineralocorticoid-induced blood pressure rise is initially due to an increase in cardiac output and in its chronic phase due to an elevated peripheral resistance. The mechanism of the increase in peripheral resistance remains unclear. © 1979 Springer-Verlag.