Liver Flashcards
liver anatomy
- receives SNS innervation from T3-11
liver lobule
- functional unit of liver
- arterioles = terminal branches of hepatic artery & portal vein
- capillaries = sinusoids
- venules = central vein
acinus
- divided into 3 zones that correspond w/ distance from arterial O2 supply
- zone 1 most oxygenated
- zone 3 least oxygenated
kupffer cells
remove bacteria before blood flows into vena cava
bile is produced by
hepatocytes
bile is stored in
gallbladder
flow of bile
canaliculi (in liver) > bile duct > common hepatic duct + cystic duct (GB) = common bile duct > duodenum
sphincter of Oddi
- controls flow of bile released from common hepatic duct
- contraction increases biliary pressure
3 functions of bile
- absorption of fat-soluble vit (DAKE)
- excretory pathyway for bilirubin & prodcuts of metabolism
- alkalinization of duodenum
cholecystokinin (CCK)
- produced in duodenum
- eating fat & protein increases CCK release & flow of bile from GB
lymph drainage
- drains into space of disse
- liver responsible for 1/2 of lymph production
liver receives ____% of CO
30%
hepatic artery
- 25% liver blood supply
- 50% O2 supply
portal vein
- 75% liver blood supply
- 50% O2 supply
liver blood flow
celiac artery provides blood flow to which 3 organs?
- liver
- spleen
- stomach
superior mesenteric artery provides blood flow to which 3 organs?
- pancreas
- small intestine
- colon
1 organ that receives blood flow from inferior mesenteric artery
colon
liver venous blood flow
- portal vein receives blood that has passed through splanchnic circulation
- not autoregulated
- increased splanchnic vascular resistance decreased portal vein blood flow
portal perfusion pressure
= portal vein pressure / hepatic vein pressure
portal HTN
- Dx:
1. portal vein pressure > 20-30 mmHg
2. sinusoids > 5 mmHg - back pressure to splanchnic organs
- splenomegaly
- varices: esophagus/stomach/intestine
- risk of hemorrhage of varices
- ascites
- spider angiomas
- hemorrhoids
- encephalopathy
hepatic arterial flow
- if portal vein blood flow decreases, hepatic arterial buffer response increases flow through hepatic artery
hepatic artery perfusion pressure
= MAP - hepatic vein pressure
Factors that reduce liver blood flow
- GA
- neuraxial
- increased splanchnic vascular resistance (SNS stimulation, pain, hypoxia, propanolol)
- increased CVP (PPV, excess hydration, CHF)
- BB
- intraabdominal surgery
- laparoscopic surgery
Hepatocytes produce
- all coag factors except vWF, 3, 4, 8
- thrombopoietin
- A1acid glycoprotein
- antithrombin
- protein c, s
- plasminogen
- albumin
Hepatocytes produce all coagulation factors except
- vWF (produced by vascular endothelial cells)
- factor 3 (same as above)
- factor 4 (diet)
- factor 8 (sinusoidal cells)
Factor 8 is produced by
liver sinusoidal cells & endothelial cells
liver metabolic functions
-glycogenesis/glycogenolysis/ gluconeogenesis
- converts ammonia to urea for elimination in kidneys
- storage of triglycerides
- synthesis of cholesterol, lipoproteins, phospholipids
- bilirubin conjugation
LFTs that assess synthetic function
- PT
- albumin
LFTs that assess hepatocellular injury
- AST
- ALT
LFTs that assess hepatic clearance
- bilirubin
LFTs that assess biliary duct obstruction
- alkaline phosphatase
- Y glutamyl transpeptidase
- 5’-nucleotidase
very sensitive for acute liver injury
PT
not sensitive for acute liver injury
albumin
marked increase AST & ALT
hepatitis
AST/ALT ratio > 2
cirrhoisis or alcoholism
most sensitive for biliary obstruction
5’-nucleotidase
hepatitis
Drug-induced hepatitis
- acetaminophen OD
- halothane
- alcohol
most common cause of acute liver failure in US
acetaminophen OD
acetaminophen OD
- max dose Tylenol = 4 g/day
- glutathione = substrate for phase 2 conjugation
- tylenol produces toxic metabolite N-acetyl-p-benzoquinoneimine
- tylenol OD consumes glutathione in liver
- leads to hepatocellular injury
- Tx = oral N-acetylcysteine w/i 8 hours OD
Chronic hepatitis
- > 6 mo
- most common cause = alcoholism
- 2nd most common = hep c
- increased liver enzymes + bilirubin + histologic evidence of liver inflammation
- S/S: jaundice, fatigue, thrombocytopenia, glomerulonephritis, neuropathy, arthritis, myocarditis
- prolonged PT
- decreased albumin
anesthetic considerations for acute hepatitis
- delay elective surgery until LFTs normal & s/s resolved
- iso or sevo
- avoid PEEP
- normocapnia
- IVFs
- regional ok if no coagulopathy
- AVOID: tylenol, halothane, amiodarone, PCN, tetracycline, sulfonamides
- decreased pseudocholinesterase activity (sux)
- decreased biliary excretion (roc)
- larger Vd
Anesthesia considerations alcoholism
- MAC decreased in acute intoxication
- MAC increased in chronic alcoholic
- alcohol potentiates GABA
- alcohol inhibits NDMA
- aspiration risk
- assume acutely intoxicated full stomach
alcohol withdrawal syndrome
- s/s 6-8 hrs after blood alcohol conc returns to near normal & peaks at 24-36 hrs
- early s/s = tremors, hallucinations
- late s/s = increased SNS, n/v, confusion, agitation
- tx = alcohol, BB, A2 agonist
delirium tremens occur 2-4 days w/o alcohol
- s/s = SZ, tachycardia, hypo/hypertension, combative
- tx = benzos, BB
Wernicke-Korsakoff syndrome
- loss of neurons in cerebellum
- vitamin B1 (thiamine) deficiency
disulfiram
- treatment for alcoholics in recovery
- hepatotoxic
- inhibits dopamine beta hydroxylase (NE synthesis) –hypotension
Cirrhosis
- cell death where healthy tissue is replaced by nodules & fibrotic tissue
- reduced number of functional hepatocytes
MELD risk
- predicts 90 day mortality
- uses bilirubin, INR, creatinine
- low risk = < 10
- intermediate risk = 10-15
- high risk = > 15 (increased M&M)
child-pugh score
Class C (10-15 points) = 80% risk periop mortality
Patho ESLD
anesthetic considerations same as acute hepatitis
TIPS procedure
- bypasses portion of hepatic circulation by shunting blood from portal vein to hepatic vein
- significant risk for hemorrhage
liver transplant
- most common indication = hep C
- preop: blood products
- RSI
gallbladder
- ## biliary stones can cause obstructive defect that impedes flow of bile as well as pancreatic enzymes. they back up into liver & pancreas
