Chapter 116 - hepatic failure Flashcards
Hepatic encephalopathy typically occurs with the loss of how much hepatic function?
70%
List compounds found in excess in circulation in HE
ammonia aromatic amino acids bile acids endogenous benzodiazepines false neurotransmitters (tyrosine, phenylalanine, methionine) GABA glutamine manganese phenol short-chain fatty acids tryptophan
Which major excitatory neurotransmitter is increased with increased levels of ammonia?
Glutamate
What is ammonia converted to in the urea cycle in the healthy liver?
Glutamine, urea
What percentage of humans with hepatic failure have cerebral edema?
up to 80%
Mechanisms of coagulopathy in liver failure?
decreased factor synthesis increased factor utilisation decreased factor turnover increased fibrinolysis & tissue thromboplastin release dysfibrinogenemia decreased platelet function & numbers vitamin K def (esp with bile duct obstruction) increased production of anticoagulants
mechanisms of pulmonary oedema in liver failure?
altered pulmonary capillary permeability
decreased albumin/COP
vasodilation
+/- endotoxemia
mechanism of PU/PD in liver failure?
- decreased urea production so defective renal medullary concentration gradient
- decreased release of ADH
- decreased responsiveness of collecting ducts to ADH
+/- primary polydipsia from central effects of hepatotoxins
possible RBC morphology changes in liver failure
target cells acanthocytes anisocytosis (nonregen anaemia of chronic disease, chronic GI bleeding, shunting) (regen anaemia if GI bleeding)
how does GGT sensitivity/specificity compare with ALP in cats with cholestatic disease?
more specific, less sensitive
why can small amounts of bilirubin in urine be normal in dogs but not in cats?
dogs can produce and conjugate bilirubin in renal tubules
cats cannot, and also have a higher threshold for bilirubin reabsorption (x9)
why is hypophosphatemia sometimes seen in hepatic encephalopathy?
centrally induced hyperventilation –> hypocapnia –> shift of intracellular carbon dioxide into the extracellular space –> increased intracellular pH –> accelerates the use of phosphate to phosphorylate glucose –> hypophosphatemia
why is fresh whole blood preferred to stored whole blood in HE patients requiring transfusion?
not as much ammonia
why are milk and vegetable proteins preferred over meat proteins for animals with HE?
lower in aromatic amino acids, higher in branched chain amino acids (valine, leucine, isoleucine), less likely to potentiate HE
MOA of vitamin E
antioxidant, prevents the action of lipid peroxidase on unsaturated bonds in hepatocyte cell membranes
