HEMODYNAMIC CHANGES IN LONG-TERM DIURETIC THERAPY OF ESSENTIAL HYPERTENSION

Thirty-eight men with untreated essential hypertension in WHO stage 1 or II, aged 19–57 years, all working, have been studied ambulatorily. Oxygen consumption, heart rate, cardiac output (Cardiogreen) and intra-arterial brachial pressure were recorded at rest in supine, sitting and standing position and during steady state work. At rest plasma volume and serum electrolytes were measured. The subjects were divided into four groups: I, untreated 7; II, chlorthalidone 100 mg every second day 9; III, polythiazide 1 mg every second day 7; and IV, hydrochlorothiazide 50 mg twice daily 15. The subjects were restudied after 8–12 months. In the untreated group none of the results at the second examination were significantly different from those at the first. In the treated groups the causal resting blood pressure and intra-arterial pressure at rest and during work were significantly lower after treatment than before. At rest when sitting, the mean arterial pressure was reduced 21, 15 and 18% in groups II, III and IV and during work a little less. Serum-K dropped significantly in all groups, the mean drop being about 0.7 mEq/1 in all groups. Plasma volume (hydrochlorothiazide group only) was 0.24 1 lower after therapy, but the difference was not significant. In the thiazide groups the pressure drop was usually associated with a drop in peripheral resistance, both at rest and during exercise. In the chlorothalidone group the pressure drop was usually caused by a reduction in cardiac index, with little or no effect on the peripheral resistance.