Liver Function Tests and Anesthesia Effect on Hepatic Fx Flashcards
tests that measure liver synthetic function include (4)
serum albumin
prothrombin time (PT/INR)
cholesterol
pseudocholinesterase
can lab tests be normal in the presence of cirrhosis
yes because the liver has a large functional reserve
liver abnormalities are typically divided into
parenchymal DO’s (hepatocellular dysfunction)
obstructive DO’s (biliary excretion)
normal total bilirubin
<1.5mg/dL (includes unconjugated and conjugated)
total bilirubin in the presence of jaundice
usually evident when total bilirubin >3mg/dL
a predominantly conjugated hyperbiliruminemia (>50%) is associated with increased urobilinogen and may reflect __________, __________ and lead to _________
intrahepatic cholestasis or extra hepatic biliary obstruction
hepatocellular dysfunction
a primarily unconjugated hyperbilirubinemia may be seen with
hemolysis orr congenital or acquired defects in bilirubin conjugation
which type of bilirubin is toxic to cells
conjugated bilirubin
transaminases
enzymes released into the circulation as a result of hepatocelluar injury
two commonly measured serum aminotransferases
aspartate aminotansferase (AST, AKA SGOT) alanine aminotrransferase (ALT, AKA SGPT)
aspartate aminotransferase
present in many tissues in addition to liver including heart, skeletal muscle, kidneys and is therefore considered nonspecific
alanine aminotransferase
present primarily in liver rand is therefore considered specific
normal AST and ALT levels
<35-45IU/L
mild elevations (<300IU/L) seen with
cholestasis or metastatic dx
serum alkaline phosphatase produced by (5) and excreted into
liver, bone, small bowel, kidneys, and placenta and is excreted into the bile
normal serum alk phos
25-85IU/L
most of the circulating alk phos comes from
bone
more alk phos is synthesized and released into the circulation in the presence of this pathology
biliary obstruction
elections up to 2x normal alk phos is associated with
hepatocellular injury or hepatic metastatic disease
normal serum albumin and half life
3.5-5.5g/dL
long half life, can be initially normal with acute liver disease
serum albumin <2.5g/dL generally indicative of
chronic liver disease
acute stress
malnutrition
two reasons hypoalbuminemia can occur that are not of liver etiology
nephrotic syndrome (albumin loss in urine) enteropathy with protein loss (GI loss of albumin)
normal whole blood NH3 (ammonia)
47-65mmol/L or 80-110mg/dL
increased NH3 usually indicative of
hepatic urea synthesis disrruption
marked elevations of NH3 usually reflective of
severe hepatocelluar damage
normal PT and significant finding
11-14 seconds
>3-4 seconds from control is significant and corresponds to an INR of 1.5
PT measures the activity of
fibrinogen, factor 2, V, VII, X
factor VII
has short half life therefore the PT is useful in evaluating hepatic synthetic function of patients with a cute or chronic liver idsease
what do you suspect with the PT does not correct within 24 hours of vitamin K administration
severe liver disease
hepatic blood flow and anesthesia
usually decreased during general and regional anesthesia due to indirect and direct effects of anesthetic agents themselves, type of ventilation, surgical procedure
diagnostic feature: pre hepatic (bilirubin overload) bilirubin: aminotransferase enzymes alkaline phosphatase prothrombin time albumin causes
diagnostic feature: pre hepatic (bilirubin overload)
bilirubin: increased (unconjugated fraction)
aminotransferase enzymes: no change
alkaline phosphatase: no change
prothrombin time: no change
albumin: no change
causes: hemolysis, hematoma reabsorption, bilirubin overload from whole blood
diagnostic feature: intra hepatic (parenchymal/hepatocellular dysfunction) bilirubin: aminotransferase enzymes alkaline phosphatase prothrombin time albumin causes
bilirubin: increased (conjugated fraction)
aminotransferase enzymes: markedly increased
alkaline phosphatase: no change to slightly increased
prothrombin time: prolonged
albumin: decreased
causes: viruses, drugs, sepsis, arterial hypoxemia, congestive heart failure, cirrhosis
diagnostic feature: post hepatic (cholestasis) bilirubin: aminotransferase enzymes alkaline phosphatase prothrombin time albumin causes
bilirubin: increased (conjugated fraction)
aminotransferase enzymes: normal to slightly increased
alkaline phosphatase: markedly increased
prothrombin time: no change to prolonged
albumin: no change to decreased
causes: stones, cancer, sepsis
volatile agents and portal hepatic blood flow
all volatile agents decrease portal blood flow. greatest with halothane, least with isoflurane
anesthetic agent and hepatic blood flow
all anesthetic agents indirectly decrease hepatic blood flow in proportion to any decrease in CO or MAP. decrease in CO also reduces hepatic BF by reflex SNS stimulation and vasoconstriction of arterial and venous splanchnic vasculature
spinal and epidural anesthesia decrease hepatic BF primarily by
decreasing BP
GA usually decreases hepatic BF by
decreasing BP, CO, and resulting SNS stimulation
ways mechanical ventilation decrease hepatic BF
controlled PPV with high mean airway pressures decrease venous return and CO
PEEP accentuates these effects
spontaneous ventilation and hepatic BF
may be most advantageous for maintaining hepatic BF
hypoxemia and hepatic BF
produces increased SNS stimulation and decreases hepatic BF
surgical procedures on or near liver and hepatic BF
can reduce hepatic BF up to 60% most likely by DNS activation, local vascular reflexes, direct compression of vessels of hepatic circulation
drugs that decrease hepatic BF
Beta blockers
alpha agonists
vasopressin
drug that can increase hepatic BF
low dose dopamine
endocrine stress response secondary to fasting and surgical stress increases levels of
catecholamines, glucagon, cortisol
endocrine stress rrersponse can at least partially blunted by
regional anesthesia
deep general
pharmacological block of SNS
CHO and protein stores are mobilized resulting in
hyperglycemia and negative nitrogen balance
opioids that can cause spasm of sphincter of odd and increase biliary pressure in order of effect
fentanyl/alfentanil (short lived) morphine meperidine butorphanol nalbuphine
two drugs to relieve opioid induced sphincter spasm
naloxone and glucagon
most common cause of postoperative jaundice
over production of bilirubin due to reabsorption of large hematoma or RBC breakdown following transfusion
hepatitis has been associated with these halogenated anesthetics
methoxyflurane
enflurane
isoflurane
hepatitis has NOT been associated with these halogenated anesthetics
sevoflurane, desflurane
risk factors associated with halothane hepatitis
middle aged
obese
female
repeat exposure, particularly within 28d
