Hepatic Surgery Flashcards
where does the liver sit in dogs and cats?
cranial abdomen
where does the liver sit in relation to the midline?
2/3 of liver mass to the RHS of the midline
how many lobes is the liver of dogs and cats divided into?
4
what are the 4 liver lobes found in dogs and cats?
left
right
caudate
quadrate
what are the lobes of the liver further divided into?
sub-lobes and processes
what is the largest liver lobe in dogs and cats?
left
what structures within the abdomen is the liver attached to?
diaphragm
right kidney
lesser curvature of the stomach
proximal duodenum
what vessel runs through the liver and is strongly attached to it?
vena cava
how many sources does the liver receive blood from?
2
what are the 2 sources of blood supply to the liver?
hepatic portal vein
hepatic artery
where does blood in the hepatic portal vein come from>
digestive tract
spleen
what is the role of the hepatic portal vein?
provides blood rich in nutrients and metabolites to be broken down in the liver
what percentage of hepatic blood flow is made up by the portal vein?
70-80%
what is the role of the hepatic artery?
provides oxygenated blood to the liver
what percentage of hepatic blood flow is made up by the hepatic artery?
20%
what percentage of oxygen supply is provided by the hepatic portal vein?
50%
what percentage of oxygen supply is provided by the hepatic artery?
50%
what does blood leave the liver through?
short hepatic veins
what do hepatic veins feed into?
vena cava
where does portal and arterial blood mix in the liver?
sinusoids
whereabouts on the liver does blood exit via hepatic veins into the vena cava?
dorsal boarder of liver
what is one of the main challenges of hepatic surgery?
haemorrhage
why is haemorrhage such a risk with hepatic surgery?
liver is a highly vascular organ
why is it essential to understand the liver’s blood supply?
to understand portosystemic shunts
what aspects of a patients care may liver impairment affect?
surgery
analgesia
anaesthesia
nursing care
when will you begin to see signs of liver damage?
once 70-80% of hepatic tissue is lost
why are signs of liver damage only seen once 70-80% of hepatic tissue is lost?
liver has high functional reserve
what are the main functions of the liver?
Synthesis and clearance of proteins (Albumin)
Metabolism of nutrients (carbohydrates, lipids, amino acids)
Production / activation of clotting factors
Clearance of toxins (ammonia, drugs, etc)
Immunoregulation (Kupffer cells)
Gastrointestinal function
Storage
what is stored within the liver?
vitamins
fats
glycogen
copper
what is the potential impact of reduced liver function on synthesis and clearance of proteins (Albumin)?
affect on albumin bound drugs and anaesthetic agents
ascites
IVFT less effective due to reduction in oncotic pressure
what is the potential impact of reduced liver function on metabolism of nutrients (carbohydrates, lipids, amino acids)?
hypoglycaemia
lethargy
weight loss
what nutrients are metabolised by the liver?
carbohydrates
lipids
amino acids
what is the potential impact of reduced liver function on production / activation of clotting factors?
clotting problems
haemorrhage
what is the potential impact of reduced liver function on clearance of toxins (ammonia, drugs, etc)?
excessive sensitivity to drugs
neurological signs
PUPD
anorexia
vomiting
what is the potential impact of reduced liver function on immunoregulation?
endotoxaemia
sepsis
what is the potential impact of reduced liver function on GI function?
weight loss
diarrhoea
where are bile acids synthesised?
in the liver
how are bile acids excreted from the liver?
excreted into hepatic ducts which drain out of the liver and converge to for the common bile duct
what forms the common bile duct?
hepatic ducts which drain out of the liver and converge to for the common bile duct
what happens to bile when the body is not undergoing digestion?
bile drains from the liver and passes via the cystic duct to the gall bladder where it is stored
where is bile stored?
gall bladder
how does bile reach the gall bladder?
passes via the cystic duct from the hepatic ducts
what is the purpose of the gall bladder?
storage and concentration of bile
how does bile leave the gall bladder when digestion is taking place?
flows from the gall bladder via they cystic duct to the common bile duct
where does bile drain to from the common bile duct?
duodenum
how does bile reach the duodenum?
drains from the gall bladder through the cystic duct and the common bile duct
what are the main functions of bile acids?
digestion and absorption of fat
neutralisation of gastric acid and inhibition of gastric acid secretion to prevent intestinal ulceration
what is the purpose of neutralisation of gastric acid and inhibition of gastric acid secretion by bile?
prevents intestinal ulceration
what tests are involved in the diagnosis of hepatic disease?
Blood tests
Urinalysis
Diagnostic abdominal imaging
what blood tests may be run to diagnose hepatic disease?
haematology
biochemistry
blood gas / electrolyte analysis
dynamic bile acid testing (bile acid stim)
what diagnostic imaging techniques may be used to diagnose hepatic disease?
radiography
ultrasonography
CT
MRI
scintigraphy
what is the best diagnostic imaging modality for diagnosing hepatic disease?
ultrasonography - provides much
more useful information than radiographs
what are the main areas of medical management used to stabilise hepatic patients?
prescription diet
oral antibiotics
oral lactulose
what is the main nutrition consideration for patients with hepatic dysfunction?
reduced levels of high biological value protein
good protein bioavailability
restricted fat
why may a patient with hepatic disease be given oral antibiotics?
to compensate for the livers reduced immunoregulatory action in detoxifying pathogens from the intestines
prevention of endotoxaemia
why may a patient with hepatic disease be given oral lactulose?
bind ammonia for excretion in faeces
reduction of risk of hepatic encephalopathy
what are the main areas of preoperative care for hepatic patients?
assessment of clotting times
IV antibiotics
IVFT
blood typing if surgery involves risk of significant haemorrhage
general patient care
what should be checked when evaluating patient clotting times?
APTT
platelets
PT
what is APTT?
activated partial thromboplastin time
what is PT?
prothrombin time
why are clotting tests essential in hepatic patients?
clotting is abnormal in ~50% of dogs with liver disease
exacerbates risk of haemorrhage
what should be done if coagulation tests are abnormal?
pre treatment with vitamin K or FFP
why are IV antibiotics indicated in hepatic patients?
due to the presence of bacteria in the liver and risk of endotoxaemia / sepsis
what would be an appropriate antibiotic for use in a preop hepatic patient?
broad spectrum antibiotic such as potentiated amoxycilin, whilst awaiting the results of culture and sensitivity testing
what drugs should be avoided in hepatic patients?
those that undergo hepatic metabolism
what is involved in IVFT provision for hepatic patients?
IVFT needed for replacement of losses via V/D
IVFT less effective due to reduced albumin and so reduced oncotic pressure
correction of electrolyte imbalances
what may require supplementation in hepatic patients?
glucose
why may glucose supplementation be necessary in hepatic patients?
may already be hypoglycaemic
can be caused by significant liver resection
what amount of liver resection may cause hypoglycaemia?
70%
what is needed to manage / assess patient hypoglycaemia?
regular blood serum monitoring
when should pr-op blood typing be performed in hepatic patients?
if surgery involves significant risk of haemorrhage (e.g. liver lobectomy)
what aspects of general patient care may be needed for hepatic patients?
more regular access to water and U opportunities due to PUPD
TTE due to anorexia
what should be done if a surgery carries high risk of haemorrhage?
blood type
cross match if previous transfusion
blood products available
what are the main hepatic and biliary surgical procedures?
liver biopsy
partial / complete liver lobectomy
surgical correction of PSS
cholecystectomy
cholecystoenterostomy
what are the main methods for liver biopsy?
US guided percutaneous (FNA or Tru-cut)
open surgical
laporoscopic
what is the benefit of percutaneous sample techniques?
less risk than surgical
what are the disadvantages of percutaneous sample techniques?
diagnostic accuracy is poor
what are the advantages of surgical liver biopsy techniques?
more accurate
yield better sample
allow gross visualisation and examination of abdominal organs
what is liver biopsy indicated for?
To establish diagnosis / prognosis where hepatic disease is suspected
what is hepatic lobectomy indicated for?
removal of masses, abscess, or in liver lobe
torsion
what are the risks associated with hepatic lobectomy?
haemorrhage
liver failure
portal hypertension
what are cholecystectomy and cholecystoenterostomy indicated for?
biliary tract rupture
bile peritonitis
diseases causing Extrahepatic Biliary Obstruction
what diseases may cause Extrahepatic Biliary Obstruction?
gall bladder mucocele
choleliths,
Pancreatitis
Neoplasia
what is cholecystectomy?
removal of the gall bladder
what is cholecystoenterostomy?
rerouting gall bladder to the duodenum
what is the most crucial part of the biliary system that should be preserved wherever possible?
common bile duct
what are the key perioperative considerations for hepatic surgery?
hypotension
hypothermia
haemorrhage
coagulation abnormalities
IVFT
premedication and induction agents
ventilation may be needed
antibiotics
what blood pressure monitoring is needed in hepatic surgery patients?
essential ideally via arterial line
what can be done to manage hypothermia in hepatic surgery patients?
close monitoring
utilise heating devices
what can be done to manage haemorrhage in hepatic surgery patients?
coagulation abnormalities screened for and appropriate treatment taken
Appropriate methods of haemostasis should be available
replacement blood products may be needed
what is the key factor in premediation and induction drug choice in hepatic patients?
avoid drugs that undergo hepatic metabolism
what are the main post operative care considerations for hepatic surgery patients?
ICU needed
analgesia
monitoring
minimum database
antibiotics
nutrition
sepsis/SIRS
how long will a patient be hospitalised for following most hepatic surgeries?
24 hours at least
longer for biliary and PSS surgery
what should be monitored in the post op period for hepatic patients?
physical parameters
BP
blood gas/electrolytes
signs of haemorrhage
leakage of bile
hypothermia
hypoglycaemia
sepsis or SIRS
what are the 2 main types of portosystemic shunt (PSS)?
congenital
aquired
what percentage of PSS are congenital?
80%
what is a portosystemic shunt?
anomalous blood vessel which connects the hepatic portal vein with the systemic circulation (e.g. caudal vena cava) thereby bypassing the liver and diverting some of the portal blood supply away from the liver
what percentage of PSS develop later in life (acquired)?
20%
why do aquired portosystemic shunts develop?
secondary to other disease like chronic portal hypertension
what are the two types of congential shunt?
extrahepatic
intrahepatic
what dog breeds to do extraheptic shunts occur more commonly in?
small breed dogs (e.g. yorkie or westie)
what dog breeds to do intraheptic shunts occur more commonly in?
large breed dogs (e.g. labradors)
what type of congenital PSS is more common?
extrahepatic
what is involved in bile acid stimulation tests?
patient is starved for 12 hours and a sample taken
they are then fed and a further sample taken 2 hours later
what tube is needed for bile acid stim?
serum
list anaesthetic considerations for a PSS patient
drug choice - non hepatic metabolism
duration of drug action
dose carefully
care with IVFT - reduced oncotic pressure
Hypoglycaemia - starvation of no more than 8 hours
hypothermia and glucose consumption through shivering
clotting times and haemorrhage risk
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