ED Board Questions Tamara Gayle, MD PGY-1

A 4 year old girl who has the classic form of Maple Syrup Urine Disease is brought to the emergency department. She recently started pre-K and has had a temperature of 39.5 since this morning with continuous episodes of vomiting. In the ED she appears very lethargic and is now very difficult to arouse on exam. She also has crackles heard in the right lower base. Of the following the best NEXT step in management is:

A. Check electrolytes B. Obtain blood culture C. CXR D. CT E. Start hydration

What is Maple Syrup Urine Disease? Autosomal recessive Due to defect in the Branched Chain Ketoacid Dehydrogenase (BCKD) enzyme, which catalyzes the breakdown of branched chain ketoacids These ketoacids form from breakdown of branched chain amino acids: leucine, isoleucine, and valine These amino acids accumulate in the blood Accumulation of leucine and isoleucine cause characteristic smell in the urine

Back to the question..  A metabolic crisis is typically caused by a stressor such as illness, trauma, etc.  Management includes:  Stop all protein intake  Provide hydration with high caloric supplementation  Correct metabolic abnormalities  Eliminate toxic metabolites  Treat precipitating factor (s)  Provide cofactor supplementation  Prevent associated sequale

Cerebral edema “Leucine encephalopathy” Increased concentrations of leucine are toxic Consider if neurologic signs such as vomiting, clonus, lethargy, etc develop If suspected obtain a CT or MRI If confirmed, infuse mannitol at 1-2 grams/kg over minutes Add IV lasix for diuresis by carefully monitor serum sodium Most common cause of death in MSUD

You are evaluating a 7mo old male who has Maple Syrup Urine Disease in the emergency department. He has not been feeding well for the past two days, because his parents feel he is coming down with a flu-like illness and is now going into metabolic crisis. Which of the following electrolyte abnormalities are you MOST likely to find:

A. Metabolic alkalosis and hypernatremia B. Metabolic acidosis and hyponatremia C. Metabolic alkalosis and hyponatremia D. Metabolic acidosis and hypernatremia E. Respiratory alkalosis and hyponatremia

Pathophysiology breakdown Catabolic stress->endogenous protein breakdown Increase in the branched chain amino acids (leucine, isoleucine, and valine) Also occurs with an excessive amount of protein ingestion Increased ketoacids and glucose utilization ketosis metabolic acidosis

Metabolic acidosis 101 Slowly correct with rehydration and high caloric intake If serum bicarb is below 14 meq/L and blood pH <7.2, give IV bolus NaHC03 as 2.5 meq/kg over 30 minutes, then 2.5 meq/kg/day until serum bicarb is meq/L Goals: Serum bicarb level over 24 mew/L Asence of ketones in urine

Sodium management Maintain serum sodium at meq/L Monitor urine sodium loss an replacement requirement As sodium apporaches meq/L, reduce IV fluids to D10 1/2NS and monitor sodium closely After 24 hours adjust sodium intake to provide 4meq/kg/day

References New England Consortium of Metabolic Programs Current Diagnosis and Treatment. Pediatrics. Sondheimer et. al. Lange. Up to date Pediatric Care Online