Physical analysis of blood serum in nephropathies and cardiopathies

Abstract

The current methods of recognizing renal insufficiency are based on the detection of a diminished rate of elimination of substances normal or foreign to body metabolism. The most reliable data are based on a study of the nitrogen, chloride and water balance. There are practical and theoretical objections to such studies. Constant diets are impracticable at Bellevue at present and there are too few workers to carry out such investigations on a large scale. On the theoretical side, we know that a diminished rate of elimination of water and chlorides does not necessarily indicate renal insufficiency but may occur in cardiac decompensation with edema.

A diminished rate of elimination must eventually lead to retention and the most accessible place to look for retention is in the blood serum. A complete chemical examination of the serum should reveal the retention of certain substances but in the case of NaCl we know that retention of NaCl and water occur together so that the concentration of NaCl in the serum remains practically constant.

In an attempt to overcome these theoretical and practical difficulties we have worked out a system of physical analysis of the blood serum which has yielded valuable information as to the relative concentration of chemical substances possessing similar physical properties. The freezing point, the refractive index, and the specific gravity of the blood serum are independent variables within certain limits. Systematic use of these methods on 50 cases, chiefly nephri tics, cardiacs, and arterio-sclerotics, has shown that definite serum pictures exist which are more or less characteristic of different types of nephritic or cardiac disease. Nephritic edema is associated with hydremia while in cardiac edema the blood serum is normal. Uremia may or may not be associated with hydremia.