Liver Failure Flashcards
What is normal plasma bilirubin?
17 μmol/L
What happens if BR is high?
If [BR] ↑s > 30 μmol/L
→ yellow sclera & mucous membranes
If [BR] ↑s > 34 μmol/L
→ skin turns yellow
What is cholestasis?
Slow/cessation of bile flow
Normally results in jaundice
Jaundice does not
What are the pre-hepatic causes of jaundice?
Haemolysis Haemolytic anaemia Toxins Massive transfusion (transfused erythrocytes short-lived) Large haematoma resorption Ineffective erythropoiesis
What are the intra-hepatic causes of jaundice?
Specific defects: ↓ed BR uptake Gilberts syndrome ↓ed conjugation BR Crigler-Najar syndrome ↓ed secretion BR into biliary canaliculi Dubin-Johnson syndrome Rotor syndrome
Intrahepatic cholestasis (↓ed outflow): Sepsis, TPN & drugs
Liver failure
Define the pathophysiology of liver failure
When rate of hepatocyte death > regeneration
Combination of apoptosis &/or necrosis
What is the clinical result of liver failure?
Clinical result = catastrophic illness
Can rapidly lead to coma/death due to multi-organ failure
What is acute liver failure?
Fulminant hepatic failure = rapid development (< 8wks) of severe acute liver injury
- impaired synthetic function (INR/PT, albumin)
- encephalopathy
- previously normal liver or well-compensated liver disease
What is chronic failure?
Over years
Cirrhosis
What are the causes of acute liver failure in the west?
Toxins
Paracetamol
Amanita phalloides
Bacillus cereus
What are the causes of acute liver failure in the west?
Inflammation
Exacerbations of chronic Hep B (Hong Kong)
Hepatitis E (India)
What are the other causes of acute liver failure?
Disease of pregnancy
AFLP/HELLP/Hepatic infarction/ Budd-Chiari
Idiosyncratic drug reactions
Single Agent: Isoniazid, NSAID’s, valproate
Drug combinations: Amoxicillin/clavulanic acid, trimethoprim/sulphamethoxazole, rifampicin/isoniazid
Vascular disease
Metabolic causes
Wilson’s disease- copper deposition
Reye’s syndrome- children taking aspirin after chickenpox
What are the causes of chronic liver failure?
Inflammation
- chronic persistent viral hepatitis
Alcohol abuse
Side effects of drugs
- folic acid antagonists
- phenylbutazone
Cardiovascular causes
- ↓venous return - right heart failure
Inherited diseases
Glycogen storage diseases, Wilson’s disease, Galactosaemia, Haemochromatosis, α1-antitrypsin deficiency
Non alcoholic steatohepatitis (NASH)
Autoimmune Hepatitis, PBC, PSC
Describe the mechanisms of cirrhosis
Necrosis of heptoctyes causes release of enzymes
Kick off cytokines
Activate Kupffer cells
Release growth factors
Stimulate hepatic stellae cell
Monocytes to macropahges
Stimulates fibroblast proliferation
Causes fibrosis and cholestasis
What are the consequences of hepatocyte failure?
Coagulopathy and bleeding Ascites Encephalopathy & cerebral oedema Hypoglycaemia Increased susceptibility to infection Circulatory collapse, renal failure
What does the decrease in protein synthesis result in?
Decreased albumin Decreased plasma (clotting factors)
What is the consequence of decreased albumin?
↓ albumin → ascites Plasma vol ↓ → 20 hyperaldosteronism → hypokalaemia (↓K+) → alkalosis
What is the consequence of decreased plasma (clotting factors)?
Hepatocytes synthesis all coagulation proteins except von Willebrand factor & factor VIIIC
What can cholestasis cause?
→ liver damage aggravates any bleeding tendency - ↓ bile salts - → ↓ micelles & absorptn of vit K - → ↓ γ-carboxylation of vit K - dependent clotting factors prothrombin (II), VII, IX, & X
What are the mechanisms of cholestasis?
Canalicular dilation ↓ cell membrane fluidity Deformed brush border Biliary transporters ↑ tight junction permeability ↓ mitochondrial ATP synthesis
What are the consequences of cholestasis?
↑ BR → jaundice Pruritus (itching) Cholesterol deposition Malabsorption Cholangitis