Potassium Levels in the Cerebrospinal Fluid after Death.

It is well known that diffusion from the red cells makes estimation of the serum potassium after death useless as a measure of its level during life. It was thought that in the cerebrospinal fluid, whose contact with blood is relatively slight, the level might rise slowly enough for its measurement to be of value. A single estimation was enough to show that this idea was false, and that potassium diffuses rapidly into the C.S.F. after death. No record of this phenomenon could be found in the literature, and some further study was thought to be indicated. The importance of potassium in nervous tissue (Cowan, 1934; Hodgkin and Huxley, 1947; Hoagland and Stone, 1948) and in the C.S.F. itself (Watchorn and McCance, 1933; Greenfield, 1936; Helmsworth, 1947) needs no emphasis. If the rate at which the potassium level rises proved regular enough, it seemed possible that the method might have some medico-legal importance as a means of estimating the time since death.