List 4 causes of an elevated serum ammonia concentration in critically ill patients
Hepatic failure
Inherited disorders of urea cycle
Drugs: Valproate, glycine, carbamezapine
Porta-systemic shunts
Increased protein load: GI bleed, TPN,
Infection with urease splitting organisms – proteus Gastric bypass, urinary diversion procedures Cancers – myeloma
Chemotherapy.
This question closely resembles, though is not identical to, Question 14 from the second paper of 2012. There, one may find a discussion of the usefulness of the serum ammonia levels in critical illness.
Here, one is merely expected to regurgitate a series of differentials.
Using a familiar template, an easily remembered list would look like this:
More detail, you beg? Impossibly large tables, useless for the purpose of rapid revision?
Vascular and cardiac causes
Infections
Neoplasms
Drugs
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Congenital causes
Autoimmune causes
Urinary and renal causes
Endocrine and Metabolic causes
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Another method of arranging the differentials, according to the physiological mechanism:
Increased substrate for ammoniagenesis
Bypass of normal metabolism
|
Acquired urea cycle defects
Congenital urea cycle defects
Excess of exogenous ammonia
Reabsorption of excreted ammonia
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