Anesthesia in Liver Patients

Question 1

what 3 main functions of the liver are relevant for anesthesia

Answer 1

1. protein homeostasis
2. drug metabolism
3. glucose homeostasis

Question 2

how is protein production relevant for anesthesia

Answer 2

ALBUMIN - required for certain drugs to bind
- if patient is hypoalbuminemic: highly protein bound drugs will have a greater free (active) portion –> requires lower dosing

CLOTTING FACTORS - coagulation during surgery

ESTERASES - small amount of drugs use esterases for metabolism

Question 3

what enzyme metabolizes the majority of drugs

Answer 3

CYP450 in the liver

Question 4

what metabolic reactions are compromised in liver disease patients

Answer 4

phase I and II

MOSTLY phase I reactions

Question 5

how does liver blood flow impact drug metabolism

Answer 5

drugs with high extraction ratio require high liver perfusion

if diseased liver has decreased blood flow –> drug metabolism decreases

Question 6

what are the 4 main effects of anesthetic drugs on the liver

Answer 6

1. decreased cardiac output –> decreased liver blood flow
2. direct liver damage
3. contraction of hepatic veins
4. systemic blood pressure

Question 7

what anesthetic drugs cause decreased CO

Answer 7

• alpha 2 agonists
• propofol
• alfaxalone
• ketamine
• inhalants

Question 8

what anesthetic drugs cause liver damage

Answer 8

• oral diazepine (cats) - acute fulminant hepatic necrosis
• NSAIDs - hepatitis
• benzodiazepines - hepatic encephalopathy

Question 9

how is liver blood flow regulated

Answer 9

autoregulation - arterial flow responds to changes in portal flow

stimulation of a1 receptors causes DECREASED arterial flow to the liver
- occurs in stress, catecholamines, and surgery

mechanical ventilation and hypoxemia decreases flow to liver

Question 10

how does liver disease affect anesthetic choices

Answer 10

liver disease alters the dose-effect response by making it less predictable

drugs tend to have a STRONGER effect in animals with liver disease due to altered pharmacology

Question 11

what drugs are impacted by impaired phase I reactions

Answer 11

• phenothiazines
• benzodiazepines
• opioids
• etomidate
• ketamine
• local anesthetics

alfaxalone - unknown but likely affected

Question 12

what drugs are NOT impacted by liver disease

Answer 12

• propofol
• isoflurane
• sevoflurane
• atracurium

do not need to alter dose

Question 13

are hepatopathies relevant to anesthesia

Answer 13

NO - only liver dysfunction

evaluate liver function paramters (albumin, BUN, cholesterol, glucose, bilirubin) prior to anesthesia

do not need to worry about ALT, AST, ALP, GGT

Question 14

what is the primary goal of anesthesia in liver disease patients

Answer 14

maintain liver oxygen delivery

relies on BP and oxygenation management

Question 15

what drug characteristics are desirable in liver disease patients

Answer 15

• do not rely on liver function
• reversible
• can be titrated to effect

Question 16

what fluids should be considered in severely hypoalbuminemic patients

Answer 16

colloids

crystalloids will further dilute the already low albumin

Question 17

what main parameters need to be monitored under anesthesia

Answer 17

oxygenation and BP
- prevent hypoxemia and hypotension

be prepared for transfusion if needed

Question 18

predmedications for liver disease patients

Answer 18

opioid +/- anticholinergic

ex. hydromorphone + atropine

anticholinergic only required if using drugs that induce bradycardia

Question 19

induction drugs for patients with liver disease

Answer 19

propofol

AVOID BENZODIAZEPINES

always preoxygenate during induction

Question 20

maintenance drugs for patients with liver disease

Answer 20

inhalant +/- opioid CRI

Question 21

what supportive measures can be used to prevent hypotension

Answer 21

fluid bolus
alter anesthetic technique