[Urea and potassium losses and changes in amino acid concentration after aortocoronary bypass operations]

Changes in urea nitrogen excretion, renal potassium losses, and changes of amino acid concentrations in plasma following aortocoronary bypass operations were observed in 10 patients. The observation time included the preoperative day, the day of operation, and 4 postoperative days. The patients were treated with a 5% glucose solution (800-1000 ml/m2). The additional spontaneous oral intake was estimated and reached approximately 600-800 kcal and 25-30 g protein on the 3rd and 4th postoperative day. The calculated urea nitrogen loss was between -8.2 g (operation day) and -11.2 g (4th postoperative day). The concentrations of serum amino acids in plasma were below normal preoperatively. It seems possible that this is due to longer preoperative fasting because only patients with normal body weight were admitted to operation. The amino acid concentrations fell significantly to lower than normal values during the postoperative period. There were massive renal losses of potassium of about 140 mEq/day on the day of operation and on the 1st postoperative day. High parenteral substitution was necessary to avoid severe falls in serum potassium levels and possible cardiac arrythmias.