Extracellular fluid volume and renal indices in essential hypertension.

Extracellular fluid volume (EFV), total blood volume (TBV), and renal indices were determined in 53 permanent essential hypertensive patients with normal renal function and balanced sodium intake and urinary output. In comparison with normal subjects, hypertensives had normal EFV values while TBV and the TBV/EFV ratio were significantly reduced (p less than 0.001). In hypertensives, a significant negative relationship (r = -0.40; p less than 0.005) was observed between the TBV/EFV ratio and diastolic arterial pressure. No correlation existed between TBV and diastolic pressure, whereas EFV (and also interstitial fluid volume) was positively related to diastolic arterial pressure (r = +0.41; p less than 0.005). Extracellular fluid volume and interstitial fluid volume were both directly correlated to the renal filtration fraction (r = +0.45; p less than 0.005). The study suggests that, in the disturbed partition of the extracellular fluid of hypertensives, changes in the interstitial space are involved and are related to variations in the renal indices.