Transcellular movement and intracellular concentration of sodium in erythrocytes after surgery and in seriously ill patients.

Abstract

Erythrocyte intracellular sodium concentration and transmembrane sodium flux were measured in nine healthy patients undergoing uncomplicated elective abdominal surgery. Intracellular sodium concentration was determined by in vitro washing of cells in a solution approximating to intracellular constituents and measuring extracellular sodium contamination with 51Cr EDTA. Sodium flux was determined by radioactive 22Na tracer both as influx and efflux. No change in erythrocyte intracellular sodium concentration or in sodium flux was found postoperatively. In 14 seriously ill surgical patients, all of whom had plasma sodium levels outside the tolerance range of our surgical population, erythrocyte intracellular sodium concentration decreased, but not significantly, compared with patients undergoing uncomplicated surgery (p = 0.16). Furthermore, sodium flux in seriously ill patients was proportional to intracellular sodium concentration. These results are at variance with the hypothesis of 'sick cell syndrome' which is said to be typified by a high intracellular sodium concentration and a reduced sodium efflux. In the surgical patients studied, it is more likely this hyponatremia does not result from a change in sodium flux but is dilutional.