Renin and body fluid volumes in chronic renal disease. Relations between arterial pressure, plasma renin activity, blood volume, and extracellular volume in chronic renal disease, as compared with essential hypertension.

In 47 patients with hypertension and chronic renal insufficiency (CRI) and 38 patients with essential hypertension (EH), the following parameters were measured under moderate salt restriction: plasma volume (PV), blood volume (BV), extracellular fluid volume (ECFV), ratio of blood volume to insterstitial fluid volume (BV/IV), recumbent plasma renin activity (PRA), increase in PRA upon standing (delta PRAst), creatinine clearance (Ccr), and mean arterial pressure (MAP). Mean PRA, ECFV, and MAP values did not differ significantly between the two groups. In the CRI group, MAP showed a weak positive correlation with ECFV (r = 0.34). Mean PV, BV and BV/IV ratio were significantly higher than in the EH group, whereas delta PRAst was markedly blunted (p less than 0.001) and showed a weak correlation with Ccr (r = 0.33). This suggests that patients with CRI on a moderate Na intake have a decreased tissue compliance which results in a relative elevation of BV. On the other hand, although MAP was not significantly correlated with either BV or IV, a negative correlation (r = -0.31) was found between MAP and BV/IV, indicating that elevation of the blood pressure (BP) tends to depress BV. These oppositely directed effects may explain the failure so far to establish a relationship between BP in renal disease and any haemodynamic parameter or combination of such parameters.