Body potassium content and capacity of elderly individuals with and without cardiac failure.

Without some measure of potassium capacity it is impossible to determine whether an individual is potassium depleted or not. Whilst weight is a useful measure of capacity in some circumstances, it is less than adequate in elderly individuals wih chronic cardiac failure. Whole body potassium has been measured in 139 patients with oedema free cardiac failure, mean age 78 years, and the results compared with those obtained in 22 healthy age-matched subjects. The results show that male and female patients have lower (94 and 91% respectively) absolute whole body potassium levels than the healthy controls though the difference are only statistically significant in females. If the body potassium results are related simply to body weight the patients are 20 and 23% depleted whereas if height is used in a regression with weight they can be considered as being 12 and 16% depleted. When the body potassium results are related to fat-free mass then the cardiac patients results are only 1 and 2% less than the healthy controls. Thus, the "potassium depletion" of patients with cardiac failure reported by others may be more a reflection of weight change rather than true cation depletion. It is concluded that fat-free mass measured from skin fold thickness is a valuable measure of potassium capacity in oedema free elderly patients with cardiac failure. The results suggest that any potassium depletion in such patients is minimal and clinically irrelevant.