Extracellular water, electrolyte and nitrogen balance after postoperative parenteral nutrition and intracellular involvement in muscle.

Brief periods of fasting or moderate trauma were previously shown to give rise to malnutrition characterized by negative nitrogen balance, reduction of lean body mass and relative increase of body water. The present study aimed to assess the possibility that brief low-calorie, low-protein parenteral fluid regimen after relatively moderate surgical trauma can modify the muscle metabolism and alter the water, electrolyte and protein composition. Well-nourished patients undergoing elective cholecystectomy were studied. During the first four postoperative days, seven patients (group I) received parenteral nutrition adequate as regards water, sodium and potassium but deficient in carbohydrates and without amino acids, while six patients (group II) had adequate parenteral supply of calories and nitrogen. The extracellular balance in regard to water, sodium, potassium, calcium, phosphorus, magnesium and urea was assessed in all 13 patients. Needle biopsy of muscle was performed during surgery and at the end of the observation period in six patients from group I and five from group II, in order to assess the total and the intracellular and extracellular water content and also sodium, chloride, potassium, magnesium, phosphorus and alkali-soluble protein nitrogen. In group I, but not in group II, there was weight loss and negative extracellular balance of all parameters, in particular potassium and nitrogen, and reduction of muscle potassium. The analyses of balance and of muscle cell composition showed considerable loss of lean body mass and indicated 'true' electrolyte disturbance, although clinical symptoms were absent and serum parameters remained normal.