- See:
- Glutamine
- Arginine
- Nitrogen Balance = Nitrogen Input - Nitrogen Output
Nitrogen Out = (Urinary Urea * 0.85) + 4 gm/dl
- Nitrogen Balance can be calculated by the Kjeldahl technique, or urea content can be measured and the result / 0.85; Nitrogen content of the TPN solution = 6.5 gm N / lit;
- Note that Nitrogen Balance calculations are inaccurate in Burns, Fistula, or Diarrhea
- Obligatory loss of 10 - 15 gm of Nitrogen lost daily in the Urine
- Each gm of Nitrogen represents 6.25 gm of muscle protein
- Hence loss of 60-90 gm of protein qd;
- Discussion:
- dose of exogenous amino acid or protein is increased until nitrogen equilibrium is achieved;
- further increases in the amino acid load appear only to enhance ureagenesis and azotemia, but not to improve nitrogen balance;
- when standard amino acid preparations are given in dosages sufficient to meet this oxidative rate, result is excessive availability of gluconeogenic aminoacids often in setting of existent hyperglycemia & excess of aromatic aminoacids, the level of which is thought to correlate with hepatic insufficiency;
- high branched chain amino acid formulae contain 45-50% branched chain amino acids, with concomitantly decreased amounts of gluconeogenic and aromatic amino aids, where as standard amino acid formulations contain 15-33% branched chain amino acids