[The relation between the density of blood and the arterial pressure in animal experiments and in patients during hemodialysis (author's transl)].

The density of arterial blood was measured continuously in animals and in human beings with an accuracy of 10(-5) g/ml by the application of the so-called mechanical oscillator technique. The density measuring device is inserted into an arterio-venous shunt. The continuous reading of the density of arterial blood allows to observe the effect of fluid shifts between the interstitial space and the plasma space. For example, lowering of the capillary pressure by the constriction of the precapillary resistance decreases the blood density by the inflow of interstitial fluid. Strong vasoconstriction apparently increases the capillary pressure and thus raises the blood density by the loss of plasma-ultrafiltrate. During hemodialysis the fluid loss into the dialysator tends to increase the blood density. However, the regulatory mechanisms of the circulation are able to keep the density of the blood at a constant value as long as possible. An increase of the density indicates a decrease of the blood volume. The new method thus allows a continuous control of the course of hemodialysis, and to avoid a critical decrease of the blood volume and of the blood pressure.