Overhydratation and renin in hypertensive patients with terminal renal failure: a hemodynamic study

Twenty-nine patients with terminal renal failure were treated by periodic hemodialysis for 2 to 18 months. Serial determinations of blood pressure, blood volume, cardiac output, exchangeable sodium and plasma renin activity were performed. Bilateral nephrectomy was performed in 17 patients and followed by a fall in blood pressure. Cardiac index was elevated in all patients but the blood pressure changes were mainly related to resistance changes. In non-nephrectomized patients, mean arterial pressure was directly correlated to plasma volume (P less than 0.0001), exchangeable sodium (P less than 0.01) and plasma renin activity (P less than 0.001). In anephric patients, mean arterial pressure was only directly correlated to plasma volume (P less than o.005). The slope of the curve relating arterial pressure to plasma volume was significantly shallower in nephrectomized than in non-nephrectomized patients, indicating a lower sensitivity of pressure to volume changes. The study provides evidence that, in hypertensive patients with chronic renal failure, the positive pressure-volume relationship is the fundamental cause of the high blood pressure and that the renin-angiotensin system acts mainly by changing the sensitivity of this mechanism.