ITE GI/Hepatic Flashcards
Mechanism of ischemia-reperfusion injury is thought to be d/t ______
disruption of sodium potassium pumps secondary to lack of ATP
3 phases of liver transplantation
- preanhepatic
- anhepatic
- neohepatic
Preanhepatic stage of liver transplant begins with incision and ends with______
cross-clamping of major vessels of liver (portal vein, hepatic a, IVC or hepatic v)
Serum ____ levels are the strongest predictor of perioperative outcomes in pts receiving TPN
albumin
Acute _____ during abdominal insufflation may result in a huge vagal response (bradycardia, brady arrhythmias, asystole)
stretching of the peritoneum
INR following donor hepatectomy peaks on postop day ___ and returns to normal by day ___. This indicates they at an anticoagulated state compared to others post op.
1-3, 5
- risk of epidural hematoma periop
Lipid emulsions are an important component of TPN bc _______ is the predominant energy producing pathway states of stress (sepsis, burns, surgery)
lipid oxidation
Nutritional support via enteral or parenteral routes should be given to all pts who are not expected to resume PO intake w/in ____ days post op
7 days
Absolute indications for TPN
- short bowel syndrome
- SBO
- Active GI bleed
- Pseudo obstruction w/ complete intolerance to food
- High output enteric cutaneous fistulas
Hepatorenal syndrome in a cirrotic pt w/ ascites has a risk of 40% at 5 years. It is caused by _____
portal HTN and resultant reduction in renal perfusion
Type 1 vs Type 2 Hepatorenal syndrome
Type 1: acute rapid renal failure w/ precipitating cause (SBP, sepsis, surgery)
Type 2: insidious onset of RF as a result of portal HTN
Portopulmonary HTN definition
pulmonary HTN (25 mmHg at rest, 30 mmHg during exercise) in a pt w/ portal HTN w/ no other known cause
Hepatopulmonary syndrome triad
- Liver dysfunction
- unexplained hypoxia
- Intrapulmonary vascular dilations (IPVDs)
Plasma albumin has a half life of ___
3 weeks
- acute decreases in liver fxn may not cause decrease in serum albumin [ ]
*PTT is a better marker of liver fxn
AST:ALT of ___ is common in alcoholic liver disease and ____ in nonalcoholic steatohepatitis
2-4
<1
(AST/ALT) is specific to hepatic origin
ALT
- think L for liver
Morbidly obese pts have an increase in _____ and ____, which can decrease the duration of action of succinylcholine and require larger doses
butyrylcholinesterase (pseudocholinesterase)
Extracellular fluid volume
Medications that should be calculated based on TBW
maintenance gtt of propofol
Succinylcholine
Neostigmine
Sugammadex
Medications that should be calculated based on lean body weight
thiopental
induction dose propofol
fentanyl, alfentanil, remifentanyl
Etomidate
Medications that should be calculated based on IBW
rocuronium
vecuronium
pancuronium
Advance liver disease, what happens to:
- platelets
- VWF
- coagulation factors
- PT/INR
- platelets: decrease
- VWF: increase
- coagulation factors: decrease (most are synth in liver)
- INR: increase
*thrombocytopenia is a well known feature of cirrhosis
2,3- DPG levels (increase/decrease) in cirrhotic pts, shifting the hgb dissociation curve to the (right/left)
increase
right
Alvimopan is a ____ receptor antagonist that (does/does not) cross the BBB
mu-receptor antagonist
- combats opioid activity in gut
- allows opioid activity in the CNS
Loperamide is a ____ used to slow gut motility and manage diarrhea
mu receptor agonist
- does not penetrate BBB
Why is using lean body weight for med dosing sometimes ideal?
It is most correlated to cardiac output
Medications that use total body weigh
fentanyl
sufentanil
propofol maintenance
thiopental
Morbidly obese pts have an (increase/decrease) cardiac output
increase
- alters elimination and delivery to kidney and liver
Morbidly obese pts have an (increase/decrease) hepatic clearance
no change
in the brain, ____ are the primary cell that metabolizes ammonia. These cells convert ammonia to _____, which acts as an osmotic agent, pulling water into the _____, and resulting in cerebral edema
astrocytes
glutamine
astrocytes
Acute hepatic encephalopathy is physiologically d/t ______ and ______
increase ammonia –> fluid shift -> swelling of the astrocytes –> cerebral edema
profound cerebral vasodilation from loss of autoregulation
Acute liver failure mortality is worse in (hyperacute/acute/subacute) liver failure
acute (8-28days) following liver injury
(acidemia/alkalemia) increases the diffusion of ammonia across the BBB and can worsen or precipitate hepatic encephalopathy in pts with chromic liver disease
alkalemia
____ is the most common medication used for both prophylaxis and tx of hepatic encephalopathy
lactulose
Effects of enteric feeds:
- Gluconeogenesis
- lipolysis
- insulin secretion
- Gluconeogenesis: decrease
- lipolysis: decreases
- insulin secretion: increase
*enteric feeds do not enter gluconeogenesis pathway,
whereas non-enteric feeds do enter gluconeogenesis pathway
______ is used by rapidly dividing cells and is a precursor of nucleotides. It is often decreased in states of stress.
Glutamine
(Hyper/Hypo)albuminemia leads to small bowel wall edema, which leads to diarrhea and malabsorption.
hypoalbuminemia
In pts with end stage liver disease, _________ can be useful in identifying the cause of a coagulation disorder
Factor VIII
- consumed in DIC
- normal or elevated in liver disease
Elevated D-Dimer is specific to DIC because _____
it indicates activation of both coagulation and fibrinolysis
Levels associated with DIC
- fibrinogen
- Factor VIII
- D Dimer
- fibrinogen: low
- Factor VIII: low
- D Dimer: high
Why are elevated AST/ALT levels (less than 2x normal) elevated in post op period?
asymptomatic preop elevations in liver enzymes
Liver disease
Surgery (blood transfusions)
Neohepatic stage of liver transplantation
reperfusion of the graft through the portal vein
- stage with greatest degree of physiologic derangements
Why is the neohepatic stage of liver transplantation associated with the most physiologic derrangements (postreperfusion syndrome)?
Large K and H+ load to central circulation
- severe and dangerous cardiac arrhythmias
*aggressively tx with calcium bicarb, insulin
Hypocalcemia effects on QRS and PR interval
narrow QRS and reduction on PR interval
QRS changes seen with marked hypothermia
J wave
- notch in downward portion of the R wave
Common anesthesia drugs in pts with or high risk for pancreatitis
propofol
droperidol MOA
aprepitant (emend) MOA
antidopaminergic
- prevent PONV
NK1 receptor antagonist
Propofol infusion syndrome sx
- metabolic acidosis
- rhabdo
- CHF
- bradycardia
Peripheral TPN can only be administered with a max fluid osm of 750. In order to provide adequate calorites with such low osm, ______ must be used
Higher fluid volumes
- not tolerated well in certain populations
STOP BANG score identifies pts with ____
severe OSA
- 6
Snore Tired Observed Pressure (blood) BMI >35 Age >50 Neck circ >40 Gender M
The __________ is the major regulator of the hepatic blood supply. Represents the ability of hepatic artery to adjust its flow in response to changes in portal venous flow. The major substance for this system is _______
hepatic arterial buffer system
adenosine
How does adenosine affect portal venous blood flow (more vs less)
adenosine
- less adenosine (good portal v blood flow): hepatic a vasoconstriction
- More adenosine (poor portal v blood flow): hepatic artery dilation to maintain stable oxygen delivery
Explain the RASS system
Angiotensinogen is produced by the liver
- converted to Angiotensin I by renin
Angiotensin I is converted to angiotensin II by ACE (lungs)
Angiotensin II is a potent vasoconstrictor and stimulates the secretion of both aldosterone and ADH (salt and water retention)
At rest, the liver receives __% of the hearts total cardiac output and __% of the body’s oxygen consumption
25%
- portal vein supplies 75%
- hepatic a supplies 25%
20%
Explain the hepatic arterial buffer response and how it regulates hepatic blood flow
A drop in hepatic portal blood flow (PBF) -> adenosine builds up in liver -> hepatic artery dilation -> increase in hepatic arterial blood flow -> increase PBF
Leading cause of periop mortality in morbidly obese
DVT leading to PE
- consider periop ac
Opioid dosing should be based on (TBW/LBW)
LBW
- if TBW, concerns for post op opioid induced ventilatory depression
Postpyloric feeds decrease the risk of (pneumonia/aspiration)
PNA
*does not decrease risk of aspiration
Compared to orogastric tubes, NGT are associated with increased risk of ____ and ____ when used for long times
sinusitis
otitis media
Why does TPN commonly cause jaundice and elevated bili levels in pts?
Cholestasis and biliary sludge
- Poss cellular necrosis
3 main categories of post-op jaundice
- overproduction or underexcretion of bilirubin
- direct hepatocellular injury
- extrahepatic obstruction
Common causes of overproduction of bilirubin
- hemolysis from blood transfusions (10% of RBCs transfused)
- hematoma reabsorption
- drug associated hemolysis
Most common periop drugs implicated in immune related hemolytic anemia
acetaminophen, insulin
Crigler-Najar is a form of severe (conjugated/unconjugated) hyperbilirubinemia, and is diagnosed (early/later) on in life
unconjugated (indirect)
early
Gilbert syndrome is an inherited autosomal dominant (conjugated/unconjugated) hyperbilirubinemia, where the primary defect is the _____ enzyme, which is responsible for conjugation of bilirubin. Bilirubin levels are usually below ___ mg/dL
unconjugated (indirect)
glucuronosyltransferase
5
Safe anesthetic drug to use in pts at high risk of hepatic encephalopathy.
Propofol
- minimally affects hepatic blood flow and oxygenation
- allows a more rapid and predictable emergence form anesthesia
TIPS procedure, the shunt is being placed between ____ and ____ circulations
portal, systemic
- effectively bypassing liver and the filtration it provides
dexmedetomidine is metabolized by the ____.
liver
- severe liver failure decreases clearance and prolongs therapeutic effect
- may mask hepatic encephalopathy in pts at high risk
Best marker for hepatic synthetic function
Most sensitive marker of hepatic dysfunction <24h
albumin (synth by liver)
PT
Clotting factors in the extrinsic pathway and Vit K dependent clotting factors II, VII, IX, and X can be assessed with _____
PT
(Prehepatic/Posthepatic) jaundice will show elevated unconjugated (indirect) hyperbilirubinemia
Prehepatic: increase unconjugated (indirect) bili
Posthepatic: inc conjugated (direct) bili
Pts with Small bowel obstruction should have ____ placed prior to induction of anesthesia.
NGT awake pt
- Decompress full stomach
- risk of aspiration
Nitrous oxide is contraindicated in SBO because _____
it causes distention of bowel by diffusing into air-filled spaces faster than nitrogen diffuses out
- 34x more soluble in blood than nitrogen
Why is metoclopramide contraindicated in SBO even though it is an anti nausea medication?
Risk of bowel perf
Dopamine antagonist
- increases gastric emptying
- pro-motility agent
- inc peristalsis
The liver receives ___% of
total cardiac output
20-30%
The hepatic artery provides __% of the blood flow to the liver, but __% of the oxygen supply to the liver.
The portal vein provides __% of the blood flow to the liver, but __% of the oxygen supply.
25%, 50%
75%, 50%
Hepatic arterial buffer response (HABR)
- When the flow in the portal vein decreases, adenosine (increases/decreases)
increases
- Adenosine will accumulate -> decreases hepatic arteriolar resistance -> increase hepatic artery blood flow -> increases delivery of oxygenated blood via hepatic a.
- HABR reaches its max effect when hepatic arterial flow is doubled.
- adenosine is a rapidly metabolized vasodilating agent
Hepatic arterial buffer response (HABR)
- When the flow in the portal vein increases, adenosine (increases/decreases)
decreases
- adenosine will be washed out from periportal regions -> increase hepatic arteriolar resistance and decrease hepatic arterial flow
- adenosine is a rapidly metabolized vasodilating agent
Which one carries more oxygenated blood to the liver, hepatic artery or portal vein?
Hepatic artery
Things other than flow that affect the Hepatic arterial buffer response (HABR)
- oxygen tension
- pH (acid base status)
- stretch receptors and smooth muscle cells w/in hepatic vasculature
Inhaled anesthetic most likely to cause liver injury?
Halothane and Chloroform
Though rare, how do these gases cause liver injury?
- Isoflurane
- Desflurane
- Sevoflurane
- Isoflurane: production of reactive intermediates
- Desflurane: Trifluoroacetic acid (TFA) reactive intermediates -> form immunogenic compounds
- Sevoflurane: very low. Hexafluoroisopropanol (HFIP) -> does not accumulate and rapidly undergoes phase II biotransformation
(Hyper/Hypo)magnesemia is associated with citrate intoxication
Hypomagnesemia
- Citrate chelates BOTH calcium and magnesium
Two major types of postop liver injuries
- Mild injury from halogenated anesthetic
2. Immune mediated severe acute hepatitis w/ widespread necrosis
Markers of cholestasis (3)
- 5’-nucleotidase
- y-glutamyl transpeptidase
- alk phos
- nonspecific for hepatobiliary disease, may be derived from bone
Alcoholic liver disease liver ratio
AST:ALT
2:4
Why is PTT or INR a better marker of liver synthetic function?
bc of the short life of factor VII (4 hours)
- The prothrombin test specifically evaluates the presence of factors VII, V, and X, prothrombin, and fibrinogen
The (PTT) specifically evaluates the presence of factors _____
Factors XII, XI, IX, VIII
- intrinsic
PT vs PTT, which one measures the integrity of the intrinsic and extrinsic system?
PT: extrinsic
PTT: intrinsic
The prothrombin test (PTT) specifically evaluates the presence of factors _____
VII, V, and X, prothrombin, and fibrinogen
- extrinsic
*A prolonged prothrombin time (PT) indicates a deficiency in any of factors
