An improved gravimetric measure of cerebral edema

Significant errors are introduced into the measurement of brain tissue water by the specific gravity technique when the edema fluid contains protein. Protein adds to the tissue solids, increasing the density of the tissue, and masks the proportional increase of brain water. Existing equations relating measured specific gravity and tissue water are not applicable, and a new formula was developed that compensates for the protein component of edema and reduces the experimental error. The new method was applied to the measurement of tissue water in cat brain made edematous by direct infusion of fluids of known composition and volume to test the theory. This technique for improving the gravimetric assessment of brain edema is presented.