Take-home point: ammonium levels are helpful in two main situations: 1) New acute liver failure (can help in prognosis) and 2) AMS of unclear etiology where a medication toxicity is suspected. Other times where hyperammonemia is suspected includes urea cycle enzyme deficiency and renal or hepatic failure.
- Common drug culprits to remember: valproic acid, 5-fluorouracil, and salicylates
- More on hyperammonemic encephalopathy from an old AM report here!
- And, a few case reports of hyperammonemia with 5-FU: http://www.ncbi.nlm.nih.gov/pubmed/8358058, http://www.ncbi.nlm.nih.gov/pubmed/21273620, http://www.ncbi.nlm.nih.gov/pubmed/17826933
Lactic acidosis: type A and type B
- Type A: from marked tissue hypoperfusion (global – as in shock, or local – as in infarct/ischemia)
- Type B: medications (albuterol, metformin, ARVs, propofol, linezolid), seizure, liver disease, D-lactic acid in DKA, malignancy (pathophys unknown), alcoholism, mitochondrial dysfunction,
Acute liver failure: 1) INR >1.5; 2) encephalopathy; 3) no e/o chronic liver disease (except, as we learned from intern report recently, it is the first presentation of HBV from vertical transmission, wilson’s disease, or autoimmune hepatitis)