[Erythrocyte potassium in premature infants small for gestational age].

A direct method was used to study the concentration of intraerythrocytic sodium and postassium in 21 prematures with adequate weight for their gestational age and in 24 small for their gestational age. Intraerythrocytic potassium showed to be less, while sodium turned out to be greater in the group of prematures small for their gestational age when compared with those with adequates weight. No significant differences were found between concentrations of serum sodium and potassium in both groups. These results are in close relationship with the findings of potassium in the muscular cell and in the leukocytes of infants with protein-calorie malnutrition and may show importance in terms of the flow of ions through the erythrocytic membrane.