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•Newborns with acute kidney injury (AKI) or end-stage kidney disease (ESKD) often receive prolonged CRRT when the early initiation of peritoneal dialysis is either contraindicated or unable to be performed. •These patients often receive total parenteral nutrition (TPN) to meet their nutritional goals. •Little to no information exists on the loss of blood amino acids (AA) and carnitine during CRRT in these patients. •The objective of this study was to determine the amino acids and carnitine losses in newborns receiving prolonged CRRT and TPN. Material and Methods

•Three newborns who received prolonged (> 2 weeks) CRRT and TPN were included in the study. Blood and CRRT effluent were simultaneously collected from these patients. •The effluent specimens were collected over 8-12 hours and the results were extrapolated to 24 hrs. Plasma was separated from blood for the analysis of 30 amino acids and free carnitine. •Amino acids in plasma and CRRT effluent were analyzed using an amino acid analyzer which uses ion-exchange chromatography and post-column ninhydrin derivatization (Biochrom System). Free carnitine was determined by HPLC-tandem mass spectrometry (HPLC-MS/MS) using flow injection, electrospray ionization and precursor ion scan. •The total amount of amino acids and carnitine received by each patient was calculated from the amino acids concentrate and carnitine added to the TPN solution. •The sieving coefficients (SQ) for each measured amino acid and carnitine was determined, while the amino acids and carnitine losses were calculated as mg/day, and as a percentage of the intake. Results •The blood flow was 50 mL/min for all three cases, and the CVVHDF clearance ranged from 68 – 115 mL/kg/hr (1.4 – 3.2 L/hr/1.73 m2). •The AA intake varied from 3.8 – 4.5 gm/kg/day. Carnitine intake was 20 mg/kg/day in two patients and 50 mg/kg/day in the third. •The SQ for all essential AAs was >0.8; in contrast, acidic AAs (glutamic and aspartic acid) had a SQ 0.84 and carnitine losses were 80% of the daily intake. •At the given high protein intake, all three patients achieved a positive N2 balance ranging from 0.45 to 0.59 gm/day.

•During CRRT, most of the AAs (including all essential AAs) are freely filtered and the quantity lost is influenced by the CRRT clearance. •In our very small sample of patients, positive nitrogen balance was achieved in all three patients with a very high (3.8 – 4.5 gm/kg/day) protein intake. •As carnitine is rapidly and freely filtered during CRRT, these patients are at risk of significant carnitine depletion. •The impact of serum AA and carnitine losses on nutritional outcome in patients with renal disease receiving CRRT is not known at this time. •Additional studies are needed to determine if these patients require special AA formulations and the degree of carnitine supplementation in their TPN to account for the AA and carnitine losses that regularly occur.

MeSH Keywords

Renal Replacement Therapy; Infant, Newborn; Amino Acids; Carnitine


CRRT; Babies


Critical Care | Medical Biochemistry | Medical Nutrition | Nephrology | Pathology | Pediatrics



1.Maxvold NJ, Smoyer WE, Custer JR, Bunchman TE. Amino acid loss and nitrogen balance in critically ill children with acute renal failure: a prospective comparison between classic hemofiltration and hemofiltration with dialysis. Crit Care Med 2000; 28(4): 1161-1165. 2.Rodigues MG, Ruzany F, Salgado DR, et al. Protein losses in continuous renal replacement therapies. Crit Care 2005; 9 (Suppl 2): P73. 3.Zappitelli M, Goldstein SL, Symons JM, et al. Protein and calorie prescription for children and young adults receiving continuous renal replacement therapy: A report from the Prospective Pediatric Continuous Renal Replacement Therapy Registry Group. Crit Care Med 2008; 36: 3239 – 45.

Presented at the AACC (American Association for Clinical Chemistry) conference.

Significant Loss of Blood Amino Acids and Free Carnitine in Newborns Receiving Continuous Renal Replacement Therapy (CRRT)



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