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PCRRT for Metabolic Disease

This article discusses the signs and symptoms of hyperammonemia in neonates, long-term effects, major causes, flow diagram for evaluation, and treatment options including alternate pathways for ammonia removal and the use of dialysis. The article also explores the use of PCRRT for metabolic disease and considerations for dialysis bath and drug clearance.

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PCRRT for Metabolic Disease

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  1. PCRRT for Metabolic Disease Timothy E. Bunchman Professor Pediatrics

  2. Signs and Symptoms of Hyperammonemia • Initially healthy appearing neonate with decompensation after several days • Often seen after institution of protein feedings • Lethargy • Poor feeding • Vomiting • Hypotonia

  3. Signs and Symptoms of Hyperammonemia • Respiratory distress, tachypnea, apnea • Irritability • Seizure activity • Neurologic deterioration leading to coma • Death

  4. Long Term Effects of Neonatal Ammonemia • Demonstrated correlation between prolonged neonatal hyperammonemic coma and brain damage with impaired intellectual functioning • Did not demonstrate correlation between peak ammonia level and level of intellectual impairment • [Msall et al. NEJM, 1984]

  5. Major Causes of Hyperammonemia • Urea cycle defects • Organic acidemias • Transient hyperammonemia of the newborn • Severe asphyxia - increased protein breakdown during hypoxic stress plus liver damage due to ischemia • Liver failure - due to multiple causes particularly infection

  6. Flow Diagram to Evaluate Hyperammonemia Urine for organic acids acidosis Increased ammonia Lactate/pyruvate No acidosis Plasma amino acids

  7. Flow Diagram to Evaluate Hyperammonemia citrullinemia Sig incr THN Nl. Plasma amino acids Nl. Or sl. increased citrulline ASA Incr. ASA low Low or absent CPS urine Orotic acid OTC Incr.

  8. Treatment of Ammonemia Prior to Further Diagnosis • Prevent further catabolism by providing adequate calories, fluids and electrolytes • Minimize protein intake • Provide alternate pathways for ammonia removal • May require exchange transfusion, peritoneal dialysis or hemodialysis for ammonia removal

  9. Alternate Pathways for Removal of Ammonia • Sodium benzoate • Cleared by the kidney at 5X the GFR • Each mole of benzoate removes one mole of ammonia as glycine SODIUM BENZOATE HIPPURATE + GLYCINE

  10. Alternate Pathways for Removal of Ammonia • Sodium phenylacetate • Easily excreted in the urine • One mole of phenylacetate removes 2 moles of ammonia as glutamine PHENYlACETYLGLUTAMINE PHENYL-ACETATE + GLUTAMINE

  11. Alternate Pathways for Removal of Ammonia • Arginine supplementation provides the urea cycle with ornithine and n-acetylglutamate • Abbreviated version of the urea cycle continues • not recommended for use in arginase deficiency or organic acidemias

  12. But what do I do when the drugs don’t work?

  13. You call your friendly dialysis folks

  14. Mode of RRT • PD • nope • Hemodialysis • looks like a good place to start • Hemofiltration • a great way to go home at night

  15. HD Rx of ammonemia(Gregory et al, Vol. 5,abst. 55P,1994:) NH4 rebound with reinstitution of HD NH4 micromoles/l Time (Hrs)

  16. HD to CRRT(prevention of the rebound) Transition from HD to CVVHD NH4 micromoles/L Time (Hrs)

  17. Local experience(McBryde et al, JASN 2000) • 18 children underwent 20 therapies of RRT due to in-born error of metabolism • mean age 56 + 7.9 mos • mean weight 15 + 3.7 kg (smallest 1.2 kg) • mean duration of therapy 6.1 + 1.3 days

  18. Local experience(McBryde et al, JASN 2000) • Modalities used • HD only-9 • time on HD 2.2 + 0.9 days • HF only-3 • time on HF 6.3 + 2.9 days • HD followed by HF-8 • time on HD + HF 10.25 + 1.8 days

  19. Local experience(McBryde et al, JASN 2000) • Outcome • 12/18 patients survived • 2/12 continued to be medication and RRT dependent

  20. But what do I do when the drugs and RRT doesn’t work?

  21. You call your friendly liver transplant folks

  22. CVVHD for NH4 Bridge to Hepatic Transplantation Successful Liver Transplantation NH4 micromoles/L Time (days)

  23. Considerations of PCRRT for metabolic disease • Dialysis Bath • “metabolic cocktail” clearance • nutritional needs with the balance of restricted protein intake and amino acid loss via HF

  24. Hemodialysis Bath Considerations

  25. Metabolic Cocktail drug clearance • Drug clearance related • small molecular weight • minimal protein binding • volume of distribution • Phenylacetate, Benzoate, Arginine all will be cleared • ? Re bolus?

  26. Comparison of Total Amino Acid losses: CVVH vs CVVHD(Maxvold et al, Crit Care Med April 2000) Amino Acid Losses (g/day/1.73 m2)

  27. Conclusion • Hyperammonemia is a medical emergency • When medical management does not work consider RRT early • HD should be used initially with HF in tandem • Liver transplant should be considered if medical and RRT management is not successful

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