Balance of total g nitrogen in = total measured g of nitrogen out + about 4 g (for insensible losses)
Positive nitrogen balance: indicates anabolism
Negative nitrogen balance: indicates catabolism
Nutrition in Renal Disease
Malnutrition in hospitalized patients is associated with increased mortality [Incidence and recognition of malnutrition in hospital [BMJ 1994; 308:945–948]
Assessment of the nutritional status of critically ill patients is limited by the unreliability of traditional markers of nutritional status in critical illness in general, and AKI in particular
Prealbumin is excreted mainly by the kidneys and hence may be falsely elevated in patients with AKI [Assessment of nutritional status in renal diseases. In: Handbook of Nutrition and Kidney. Mitch WE, Klahr S (Eds). Philadelphia: Lippincott Williams & Wilkins, 2002, pp. 42–92]
Patients with AKI are hypercatabolic with a negative nitrogen balance (165), resulting from both increased protein catabolism and impaired protein synthesis
Continuous Renal Replacement Therapy (CRRT)
There is Markedly Increased Protein Catabolism in Most Patients Requiring CRRT: the use of CRRT enhances the clinician’s ability to provide adequate nutrition because of an improved ability to manage volume
Unfortunately, the recommended amount of protein in this population remains controversial and recommendations are based solely on expert opinion, because there are no data available from RCT
Although there are no studies demonstrating a benefit in outcomes (e.g., survival or dialysis-free days), consensus recommendations include nonprotein caloric intake of 20 to 30 kcal/kg body weight per day and a protein intake of 1.5 g/kg per day (168).
However, several studies have demonstrated a less negative or even positive nitrogen balance in those patients receiving up to 2.5 g/kg per day while receiving CRRT without evidence of adverse effects (169 –171).
An increase in nonprotein calories in critically ill patients with AKI does not improve nitrogen balance (172).
Nutritional effect of continuous hemodiafiltration. Nutrition 1995; 11:388–393
Impact of the nutritional regimen on pro-tein catabolism and nitrogen balance in pa-tients with acute renal failure. JPEN J Parenter Enteral Nutr 1996; 20:56-62
High protein intake during continuous hemodiafiltration: Impact on amino acids and ni-trogen balance. Int J Artif Organs 2002; 25:261–268
Prospective randomized trial to assess caloric and protein needs of critically Ill, anuric, ventilated patients requiring continuous renal replacement therapy. Nutrition 2003; 19:909–916