In the present report the plasma potassium concentration of premature infants of varying ages and weight is presented and the range of the "normal" concentrations established, taking into account the effect of the dietary intake and the age of the subjects.
The potassium content of a formula for feeding the premature infant was changed by altering the carbohydrate content of the formula and by adding various salts of sodium, potassium, and calcium. The effect of these changes on the plasma concentration of potassium was observed.
The data obtained are interpreted to indicate that the factors which affect the plasma concentration of potassium in the premature infant appear similar to those which have been identified in the adult.
Clinically well infants were studied. Infants weighing less than 5½ lb. (2.5 kg.) at birth were considered to be premature. The temperature of the nursery was maintained between 24 and 27