Acute Alterations of Body Composition after Open Intracardiac Operations

The body composition of patients with heart disease is acutely altered by surgical intervention. Interrelations and causes of the alterations have not been clear. Twenty patients were studied preoperatively and again 2 to 4 days after open intracardiac operations. In nine, measurements were made of the volumes of total body water, extracellular water, plasma, and red cells, and of the amounts of total exchangeable sodium and potassium. In an additional four patients total exchangeable sodium and potassium were measured, and in another seven only exchangeable sodium was measured. Calculations were made of the intracellular and extracellular distribution of water and potassium. The significant changes (P < 0.05) occurring during the interval between studies were increase in extracellular water (7%), interstitial water (12.5%), and exchangeable sodium (9.4%), decrease in total exchangeable potassium (8.5%) and amount (8.7%), and concentration (6.9%) of calculated intracellular potassium. Uptake of sodium and water by the patient during cardiopulmonary bypass and postoperative loss of intracellular potassium with its secondary renal excretion are postulated as being etiologic. These findings imply that sodium intake in the early postoperative period should be low, water intake no more than urinary and insensible losses, and that potassium should be administered.