Interrelationship between the pathophysiology and antihypertensive treatment in benign essential hypertension.

Abstract

In order to obtain further information on the fundamental relationship between the pathophysiology and the treatment of hypertension, the following variables were measured; plasma volume (PV), extracellular fluid volume (ECFV), total exchangeable sodium (Nae), plasma renin activity (PRA), plasma concentration (pNA) and twenty-four hour urinary excretion of noradrenaline (uNA) together with pressor response to infusion of 0.3 μg/kg/min of noradrenaline (NA response) in patients with uncomplicated essential hypertension. Immediately after admission, supine pNA was positively correlated with diastolic blood pressure (DBP; r = 0.396, p<0.005) and with mean arterial pressure (MAP; r = 0.293, p<0.05) in all hypertensive patients. This correlation was most outstanding in young patients (under 40 years of age; r = 0.752, p<0.01 ), or less but was still significant in the middle aged group (from 40 to 59 years; r = 0.477, p<0.05) and not significant in the older group (over 60 years old). On the other hand, significantly higher pNA and lower PV, ECFV and Nae were observed in patients with normal PRA (NRH) as compared with low PRA (LRH), whereas a remarkable relationship was observed positively between pNA and DBP (r = 0.405, p<0.02) and negatively between PV (r= -0.444, p<0.02), ECFV (r = -0.544, p<0.01) or Nae (r= -0.601, p <0.01 ) and MAP in NRH, but not in LRH. Following two weeks of rest, with a regular diet (Na 256-300 mEq, K 75 mEq), after admission, MAP and uNA decreased and PV, Nae and NA response increased significantly. The reductions of MAP following 2 weeks of rest were significantly correlated with values in pNA and uNA immediately after admission and with the decreases of uNA following 2 weeks of rest. After 2 weeks of rest, a significantly positive orrelation was observed which was more marked in LRH than NRH, between MAP and PV, ECFV or Nae, while no relationship could be detected between MAP and pNA. Following one week of sodium restriction (Na 35, K 75 mEq), MAP, PV and NA response decreased, and pNA and PRA increased significantly. And, following 4 weeks of sodium restriction, a significantly positive correlation was found between the changes in MAP and those in PV (r = 0.7 1 9, p<0.01 ) or Nae (r = 0.686, p<0.025). Following 2 weeks of sodium loading (Na 390, K 75 mEq), MAP, PV, Nae and NA response increased, whereas uNA and PRA decreased significantly. The elevation of MAP in LRH was significantly greater than that in NRH. These findings suggest that in patients with uncomplicated essential hypertension, the enhancement of sympathetic nerve activity may play an important role in maintaining the level of blood pressure, particularly, in younger patients or in patients with NRH or HRH. On the other hand, the role of volume factors may be quite important in hypertensive mechanisms in older patients or in LRH. Therefore, as the antihypertensive treatment, a definite release of physical and mental stress, beta-blockade or sympatholytic drugs should be chosen as an adequate treatment in the former, and sodium restriction or diuretic agents should be selected in the latter.