'Sick cell' hyponatraemia and gastrointestinal electrolyte loss.

A patient with protracted vomiting was noted to have hyponatraemia and hypokalaemia on admission. Isotope dilution studies before treatment revealed profound body depletion of sodium, potassium and water. Treatment with potassium chloride tablets produced a simultaneous rise in serum sodium and potassium concentration without change in urine volume or osmolality, or body weight. Potassium depletion appears to have contributed to the mechanism of hyponatraemia in this situation, and that replacement of potassium corrected hyponatraemia by effectively re-distributing solute and water across the cell membrane, so that sodium ions which had entered intr-cellular fluid during electrolyte depletion, subsequently returned to extracellular fluid after treatment.