Amino acid loss and nitrogen balance in critically ill children with acuterenal failure: A prospective comparison between classic hemofiltration andhemofiltration with dialysis

Hypothesis: Amino acid (AA) loss is not equivalent on continuous venovenous hemofiltration (CVVH) compared with continuous venovenous hemodiafiltratio n (CVVHD). Amino acid supplementation may be necessary to adjust for a grea ter clearance on CVVH to maintain nitrogen balance similar to that of CVVHD . Objective: To compare AA losses and nitrogen balance between CVVH and CVVHD in children with acute renal failure. Setting: Pediatric patients in the pediatric intensive care unit of a terti ary referral center. Design: Prospective randomized crossover study in consecutive children who required hemofiltration. Patients: A total of 12 plasma clearance studies for AA and urea, consistin g of 24-hr collections of ultrafiltrate and urine for nitrogen balance, was performed on six patients during CVVH and CVVHD. Patients received total p arenteral nutrition (TPN) with caloric intake 20% to 30% above their restin g energy expenditure measured by indirect calorimetry and 1.5 g/kg/day prot ein of TPN. Study conditions were comprised of 2 L/hr/1.73 m(2) of dialysat e or prefiltered replacement fluid and hemofilter flow rates of 4 mL/kg/min were maintained for all patients. Methods and Main Results: Amino acid clearances were greater on CVVH than C VVHD, except for glutamic acid, where clearance was 6.73 +/- 2.31 (SEM) mL/ min/1.73 m(2) on CVVH and 7.59 +/- 2.79 mL/min/1.73 m(2) for CVVHD (NS). Th e clearance difference between the two modalities was 30%. Urea clearance w as equivalent (30.1 +/- 1.74 mL/min/1.73 m(2) and 29.0 +/- .97 mL/min/1.73 m(2)) for CVVH and CVVHD, respectively. Amino acid loss on CVVH and CVVHD w as similar (12.50 +/- 1.29 g/day/1.73 m(2) vs. 11.61 +/- 1.86 g/day/1.73 m( 2), respectively), representing 12% and 11%, respectively, of the daily pro tein intake. The catabolic state, as measured by urea nitrogen appearance, was high for all patients during the 48-hr study period with a mean of 291 mg/kg/day during CVVH, and 245 mg/kg/day for CVVHD. Nitrogen balance varied from a negative 12.95 g/day/1.73 m(2) to a positive 4.93 g/day/1.73 m(2) o n CVVH and a negative 7.69 g/day/1.73 m(2) to a positive 5.50 g/day/1.73 m( 2) on CVVHD. Conclusions: Clearance of AA is greater on CVVH than on CVVHD, but no signi ficant difference in AA loss was present between the two therapies. Nitroge n balance often is not met on either therapy when a standard 1.5 g/kg/day p rotein and a resting energy expenditure of 120% to 130% of calories is deli vered by TPN.