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Liver wt percent of body weight
liver functional unit
How much blood can the liver store?
up to 500 ml
- Many and various including:
- filtration and storage of blood
- CHO metab
- bile formation
- Iron and vitamin storage
- Manufacture of coag factors
T or F, the liver lobule is constructed around a central vein that empties into the hepatic veins, then the vena cava
What are the liver sinusoids?
Lie in-between the liver cell plates and the central vein, allow the hepatic cells to be constantly exposed to portal venous blood
What 3 cell types line the venous sinusoids?
- 1) hepatic cells
- 2) endothelial cells
- 3) Kupffer cells
What is another name for the Kupffer cells?
What is the significance of the Kupffer cells?
Describe the endothelial lining of the sinusoids
Made up of large pores so plasma substances can easily move in (even large proteins)
spaces of Dissi
- lies beneath the endothelial cell lining
- connects with the lymphathic vessels
location where portal vein and hepatic artery enter the liver and the hepatic ducts leave
- enters the liver at the port hepatis
- made up of: hepatic artery, portal vein, and bile passages
Liver blood flow
100 ml / min / 100 g of tissue
Liver blood flow is ____% of CO
From what 2 sources does the liver receive blood from? How much from each?
- Portal vein 70%
- Hepatic artery 30%
Describe the portal venous blood
- poorly oxygenated but nutrient rich
- still supplies the liver with 50% of O2 supply
- carries blood from the GI tract
- carries toxins to the liver
Describe the hepatic arterial blood
- well oxygenated
- supplies the liver with 50% of its O2
What receptors are in the portal vein?
alpha 1 and dopamine
Portal vein mean pressure
10 mmHg or less
Hepatic artery mean pressure
The liver has ____ blood flow and ____ vascular resistance
What organs contribute to the de-oxygenation of the blood in the portal vein?
Pre-portal tissues (stomach, spleen, pancreas, small intestine, and colon)
Where does the hepatic artery receive blood from?
- Branch of the celiac trunk
What is reciprocity of flow
The hepatic artery can dilate to increase blood flow to the liver when blood flow from the portal vein decreases
What receptors does the hepatic artery contain?
alpha 1, dopamine, and cholinergic
T or F, the portal vein system communicates with the systemic venous system in a number of locations
Where do cholesterol and bile salt production occur?
- Bile is then stored in the gall bladder
What are bile salts needed for?
Absorption of fatty acids, fat soluble vitamins (A, D, E, K), dietary cholesterol, and other lipids
How is the liver involved in coagulation?
- Formation of numerous blood factors and fibrinogen
- Kupffer cells remove FSP from the circulation
- Plasma activators of fibrinolysis are cleared by the liver
- Conjugates bilirubin (from RBC breakdown)
- Stores excess iron
How is the liver involved in CHO metabolism?
- Gluconeogenesis (formation of glucose from non-CHO sources)
- Glycogenesis (storing glucose as glycogen)
- Glycogenolysis (breakdown of glycogen into glucose)
How much glycogen can be stored in the liver
How is the liver involved in fat metabolism?
- Excess CHO and protein are converted to fat
- Formation of lipoproteins needed for FA transport
- Oxidation of FA to acetoacetic acid (becomes acetyl Coa, intermediary in Krebs cycle)
How is the liver involved in protein metabolism?
- Albumin synthesis, 10-15 g/ day
- 80-90% of capillary oncotic pressure
What hormones is the liver responsible for removing?
Aldosterone, ADH, GABA, cortisol, sex hormones
How is the liver involved with drug detox?
- Phase 1 and 2 reactions (create a polar water soluble substance that can't be reabsorbed by the kidney)
- Managed by CP450 system in the liver
How are the levels of cholinesterase altered in liver disease?
What diseases affect the liver parenchyma?
Hepatitis and cirrhosis
Most common type of hepatitis
What are examples of systemic diseases that also affect the liver?
cytomegalovirus and Epstein-Barr virus
What lab marker is indicative of viral hepatitis
elevated amino transferase level
- very contagious
- fecal oral contamination
- virus shed in stool for days prior to symptoms and during 1st 1-2 weeks of clinical illness
- usually self limiting and does not cause chronic hepatitis or cirrhosis
When are is hep A no longer contagious?
by 3rd week of clinical illness
2nd most common cause of acute hepatitis in the US
hep B, C, and D transmission
parenterally, sex, mother to fetus
T or F, hep B and C are not screened for in blood products
What percent of hep C cases are from IVDA?
Most common cause of liver transplantation
hep C associated cirrhosis
Hep D is reliant on hep ___ for replication
B, thus only occurs in pts with hep B
How is hep E spread? Is it common in the US?
S/sx acute hepatitis
- dark urine
- N/V, anorexia
- RUQ pain
- hepato and splenomegaly
- light colored stools
Lab findings with acute hepatitis
- Increased: ALT, AST, bili
- increased PT
Normal value for total bili
0.3-1.9 mg /dl
T or F, jaundice and elevated AST and ALT occur simultaneously with acute hepatitis?
F, AST and ALT are elevated first and decrease just before jaundice peak
T or F, the degree of aminotransferase elevation correlates with severity of disease?
F, however if conc < 500 IU/L, then hepatitis is usually mild
What type of acute hepatitis is most likely to result in chronic hepatitis?
Hep C, 60-75%
Acute hepatitis treatment
T or F, acute hepatitis is usually uneventful and liver function returns to normal
How many years of protection does the hep A vaccine provide?
Prevention of acute hepatitis
- avoid exposure
T or F, acute hepatitis does NOT increase the risk for chronic hepatitis or hepatocellular carcinoma
How can a tylenol OD cause acute hepatitis?
Tylenol is conjugated by glutathione, the stores get depleted with excess tylenol. Toxic metabolites accumulate and destroy liver cells.
What volatile is most associated with a post-op decrease in liver function?
Halothane, but can occur with any volatile due to decreased liver blood flow
Lab values of bill, AST & ALT, and alk phos associated with pre-hepatic dysfunction
- incr unconjugated bili
- normal AST, ALT, and alk phos
Causes of pre-hepatic dysfunction
hemolysis, hematoma resorption, bili overload
Causes of intra-hepatic dysfunction
viral, drugs, sepsis, hypoxemia, cirrhosis
Causes of post-hepatic dysfunction
biliary tract stones and sepsis
Lab values of bill, AST & ALT, and alk phos associated with intra- and post-hepatic dysfunction
Incr conjugated bili, incr AST and ALT, incr alk phos
How do the s/sx of acute hepatitis compare with chronic?
Lab abnormalities assoc with chronic hepatitis
- elevated AST and ALT
- decr albumin
- incr PT
T or F, age at time of diagnosis is a significant determinant of chronicity
T, 90% of infected neonates become carriers
Common causes of chronic hepatitis
- autoimmune (see increased bili)
- Hep B and C
- Wilson's disease
- alpha 1 anti-trypsin deficiency
- primary biliary cirrhosis
- primary sclerosing cholangitis
Most common reason for liver transplant
chronic hep C with liver failure
What drugs can cause chronic hepatitis
methyl dopa, trazodone, isoniazid, sulfonamide, tylenol
result of scarring of liver parenchyma from chronic hep C or LT ETOH use
Primary biliary cirrhosis
- can cause cirrhosis
- immune mediated
- more common in women ages 30-50
- may be associated with other auto-immune diseases
Why does portal HTN develop with cirrhosis
Result of increased resistance due to damaged liver cells
- portal HTN
- bacterial peritonitis
- hepatorenal syndrome (poor prognosis)
- gastroesophageal varices
Portal HTN, combined with decreased serum _____, increased _______, and increased ____ factors can cause ascites
albumin, VC, anti-natruitic
What issues can result from portal HTN? Ex: esophageal varices
hemorrhoids, capamedusae (dilation of paraumbilical veins)
- transjugular portosystemic shunt
- used for tx of portal HTN
- provides a conduit for portal vein blood flow to flow directly into the hepatic vein, thus bypassing the liver parenchyma
- occurs in cirrhosis
- likely due to increase in circulating VD endotoxins
- decreased SVR
- CO > 14 LPM
- arterial hypoxemia (PaO2 50-70 mmHg)
- hyperdynamic circulation
- impaired immunity
- hepatic encephalopathy
- primary hepatocelluar carcinoma
Why does pruritis occur with cirrhosis?
- Decreased bili conjugation and excretion
- Bile salts accumulate in the skin and cause pruritis
Factors that contribute to development of ascites in cirrhosis
- Low albumin
- Increased Na and water retention
- Portal HTN
Med management of ascites
removal with a K sparing diuretic (aldosterone antagonist), max diuresis 1L/ day
Surgical management of ascites
- Levine shunt, 1 way valve that diverts fluid from peritoneal cavity to IJ (rarely used)
- Paracentesis (acute removal of fluid)
What is the Child-Turcotte-Pugh (CTP) score?
- Used to evaluate peri-op risk for cirrhosis pts
- Looks at bili, albumin, INR,encephalopathy, nutrition, and ascites
Your pt scored a 14 on the CTP scale? What type of risk are they? Can they have elective non cardiac surgery?
- High surgical risk
- Mortality rate= 50-80%
- Not recommended
- SE of cirrhosis
- from intrapulmonary AV shunting of blood
- clinical features include orthodioxyia (fall in blood O2 upon standing) and platypnea (dyspnea relieved by laying down)
For major surgery for a pt with liver disease, an INR of _____, Plt ______, and fibrinogen of ____ is preferred.
- INR < 1.5
- Plt > 100K
- Fibrinogen > 100 mg / dl
Why is it especially important to maintain normothermia and use strict aseptic technique in pts with liver failure
increased risk for infection
Anesthesia goals for liver disease
- maintain hepatic blood flow (N20 and barbiturates will decr hepatic blood flow the least)
- preserve liver function
How do the volatiles affect hepatic blood flow?
- Iso and des may preserve reciprocity of flow by dilating the hepatic artery
Why is hyperventilation harmful to a liver disease pt?
- Increases intrathoracic pressure and thus decreases hepatic blood flow
- Increases ammonia levels (ammonium goes to ammonia)
Liver failure pts- std induction or RSI?
RSI due to aspiration risk
Is regional anesthesia ok for a liver failure pt?
Yes, presuming coags are WNL, but they're usually not...
Why is drug half life increased in liver disease?
T1/2= Vd/ Cl
Vd is increased and Cl is decreased
With what drugs should we use caution with in a liver disease pt?
- Benzos (phase 1 metab, incr DOA)
- Opioids (morphine and demerol both have active metabolites)
- Vec and roc
What is the NMB of choice for liver disease?
Succ or cisatro
Mortality rate for class C liver disease pts
- so monitor these pts for at least 24 hrs in ICU or step-down
Fulminent liver failure
- ALF with hepatic encephalopathy
- develops within 2-8 weeks of illness in a pt without pre-existing liver disease
How can ALF be differentiated from chronic liver failure?
ALF- non specific symptoms of fatigue and malaise in a previously healthy person are quickly f/b jaundice, MS changes, and maybe coma
Anesthesia implications of ALF
- correct coags
- caution with meds
- monitor for hypoglycemia, acid base, lytes
- transfuse slowly (risk for citrate intoxication)
- maintain hepatic blood flow and oxygenation
- strict aseptic technique
What is the only cure for severe acute liver failure?
What percent of liver transplants are due to hep C related liver disease?
What is the 1 yr and 5 yr survival rates for liver transplant?
3 stages to liver transplant procedure
- 1) Dissection (pre-anhepatic)
- 2) Anhepatic
- 3) Reperfusion
Contraind to liver transplant
- incurable malignancy
- adv age
- active systemic or incurable infection (hep C)
- current ETOH use
- major systemic disease
- morbid obesity
What are possible issues with phase 1 of liver transplant?
- HD instability from blood loss, venous pooling, decreased venous return from surgical retraction
- Coag issues
Risks associated with venovenous bypass
- VAE or thromboembolism
- risk of decannulation
During what phase of liver transplant is venovenous bypass performed?
Why is venovenous bypass used?
- Complete cross clamp of the IVC is often not tolerated due to decreased CO and venous return
- VVB helps to maintain HD stability and to decrease bleeding from engorged portal system
- Delays onset of metabolic acidosis
- Maintains renal function
VVB drains blood from ______ and after it is drained thru a pump, gets returned to the body via the _________.
- the LE (common iliac veins)
- axillary or jugular vein
What blood products are acceptable to give during VVB during the pre-anhepatic phase of liver transplantation ?
- PRBCs and FFP ok
- Avoid Plt and cryo during VVB
Common issues during the an hepatic phase of liver transplant
blood loss, coag issues, acidosis, hypothermia, decreased renal function, inability to metabolize drugs
When does the an hepatic phase begin
when blood supply to the native artery is stopped by clamping the hepatic artery and the portal vein
What interventions can be performed to prepare the pt for reperfusion during liver transplantation
- 100% O2
- have emergency drugs and equipment available
- ensure pt has adequate IV volume before flushing the portal vein
When does the neohepatic or reperfusion phase begin?
when portal vein, hepatic artery, and IVC are unclamped
What issues are possible during the neohepatic phase of liver transplant?
- HD instability (arrhythmias, bradycardia, hypotension, hyperkalemic arrest)
- coag issues
What is the most critical time during liver transplantation?
What issues are possible during reperfusion syndrome?
- volume overload
- HD instability
- profuse bleeding
- pulmonary edema
- pulm HTN
- hypoCa (myocardial depression)
Anesthesia goals during reperfusion phase of liver transplant
- adequate perfusion pressure (MAP~70 mmHg)
- high UO
- aseptic line insertion
K level should be _____ prior to reperfusion.
- <4 meq/ L
- will elevate with reperfusion
During liver transplant, when should the volatile be shut off?
5 mins before reperfusion phase
What blood products should we have available for a liver transplant pt?
Why do we want to avoid direct acting vasopressors during liver transplantation?
Want to maintain liver perfusion (alpha 1 receptors in hepatic artery and portal vein)
- hyperacute due to performed antibodies
- microvascular clots and thrombosis results
happens up to 5 days post-op
What is evidence that the transplanted liver is working?
- Increased ionized Ca (reflects citrate metabolism)
- Correction of acidosis
- Correction of blood glucose (glycogen release)
- Bile formation
- Reduced need for HD support
- Metab of muscle relaxants and other drugs
The 1st ____ hrs after liver transplant are critical. The surgeon will know within ___ to ___ hours if the new liver is working.
T or F, a living person can donate a portion of their liver to another person
Cirrhotic pts tend to do better with a donor liver that is as large or not larger than the native liver, T or F?