Amino acid clearances and daily losses in patients with acute renal failure treated by continuous arteriovenous hemodialysis

OBJECTIVE: To determine daily amino acid and total protein losses in patients with acute renal failure receiving total parenteral nutrition (TPN) during treatment by continuous arteriovenous hemofiltration with hemodialysis (CAVHD). DESIGN: Prospective, nonrandomized study. SETTING: Patients in the ICU of a regional nephrology referral center. PATIENTS: Eight clearance studies of individual amino acids were performed in six patients with acute renal failure receiving TPN. Daily nitrogen intake was 9 g (one patient), 14 g (two patients), and 18 g (three patients). The clearances of individual amino acids were measured at two dialysis flow rates to calculate daily amino acid and total proten losses. RESULTS: Amino acid clearance rates ranged from 7.8 +/- 2.2 (glutamic acid) to 25.2 +/- 4.8 mL/min (3-methylhistidine) at a dialysate flow rate of 1 L/hr and from 13.6 +/- 1.7 (tryptophan) to 33.7 +/- 4.3 mL/min (3-methylhistidine) at a dialysate flow rate of 2 L/hr. These results represent daily amino acid losses of 1.5 +/- 0.4% (glutamic acid) to 111.6 +/- 16.6% (tyrosine) of the nutritional input at a dialysate flow rate of 1 L/hr and 2.1 +/- 0.6% (glutamic acid) to 145.8 +/- 17.8% (tyrosine) at a dialysate flow rate of 2 L/hr. Total losses would represent 8.9 +/- 1.2% and 12.1 +/- 2.2%, respectively, of the daily protein input. CONCLUSIONS: These studies confirm that amino acid clearances are relatively high during CAVHD and daily losses should therefore be considered.