Observations of serum potassium in patients undergoing cardiopulmonary bypass.

not apply during the movement of potassium across the cell membrane as a result of acute trauma. The extracellular space contains only 2% ofthe total exchangeable potassium in the body, hence minor fluctuations in the net movement of potassium across the large cell membrane component may produce marked changes in the serum level.14 In addition, elevations ofthe extracellular potassium concentration stimulate the entry of potassium into the cell and control any major fluctua¬ tions in the serum potassium.30 Potassium balance in heart disease