Hepatic Surgery Flashcards
where does the liver sit within the abdomen?
cranially, with 2/3rds of it mass to the RHS
how is the liver divided?
4 lobes - left, right, caudate and quadrate
what is the liver attached to?
diaphragm, right kidney, lesser curvature of the stomach and proximal duodenum
which major vessel runs through the liver?
caudal vena cava - firmly attached to liver
where does the liver receive blood from?
hepatic portal vein (from digestive tract and spleen) - 70-80%
hepatic artery - oxygenated blood - 20%
where does the oxygen supply to the liver come from?
50% hepatic portal vein and 50% hepatic artery
how does blood leave the liver?
drains into hepatic veins which exit at the dorsal border of the liver into the caudal vena cava
what is one of the main challenges of hepatic surgery?
high vascularity of the liver
when do we start to see clinical signs of hepatic impairment?
not until 70-80% of functional hepatic tissue is lost - large functional reserve
what might we see if synthesis and clearance of proteins (albumin) is impaired?
albumin-bound drugs and anaesthetic agents, ascites
what are the main functions of the liver?
synthesis and clearance of proteins (albumin)
metabolism of nutrients
production/activation of clotting factors
clearance of toxins (ammonia, drugs)
immunoregulation
GI function
storage - vitamins, fats, glycogen, copper
what might occur as a result of impaired metabolism of nutrients?
hypoglycaemia, lethargy, weight loss
what might occur as a result of impaired clearance of toxins?
excessive sensitivity to drugs, neurological signs, PUPD, anorexia, vomiting
what might occur as a result of impaired production/activation of clotting factors?
clotting problems, haemorrhage
what might occur as a result of impaired immunoregulation?
endotoxaemia, sepsis
what might occur as a result of impaired GI function?
weight loss, diarrhoea
what are some of the non-specific signs you might see with impaired liver function?
PUPD, lethargy, weight loss
where are bile acids synthesised?
in the liver
how are bile acids excreted?
into hepatic ducts - converge to form common bile duct
what happens to bile when the body is not digesting?
bile drains from the liver and passes via the cystic duct to the gall bladder
what happens to bile in the gallbladder?
storage and concentration
how does bile exit the gallbladder?
flows out via the cystic duct to the common bile duct and into the duodenum
what are the main functions of bile acids?
help with digestion and absorption of fat
neutralise gastric acid and inhibit gastric acid secretion to prevent intestinal ulceration
what diagnostic testing might be carried out for suspected hepatic dyfunction?
blood testing - haematology, biochemistry, blood gas/electrolytes, dynamic bile acid testing
urinalysis
imaging - radiography, U/S, CT, MRI, scintigraphy
how might we medically manage patients with hepatic dysfunction to help with stabilisation before surgery?
prescription diet
oral abs
oral lactulose
what should be ascertained about the patients blood before surgery?
complete coagulation profile - platelet count, activated partial thromboplastin time, prothrombin time
why should a complete coagulation profile be carried out before hepatic surgery?
hepatic insufficiency can lead to clotting abnormalities, which could exacerbate risk of haemorrhage
how can we mitigate abnormal coagulation test results?
advisable to pre-treat patient with vitamin K or fresh frozen plasma
why are abs indicated for hepatic surgery?
due to presence of of bacteria in liver and risk of endotoxaemia/sepsis
what is an appropriate ab choice for a patient undergoing hepatic surgery?
broad-spectrum ab e.g. potentiated amoxycillin or 2nd gen cephalosporin (while awaiting C&S results from liver/bile/gallbladder)
which types of drugs should be avoided in patients with hepatic insufficiency?
drugs than undergo hepatic metabolism
what general patient care is important to consider in patients with hepatic insufficiency?
pupd - regular water replenishment and toileting trips
anorexia - tempt to eat
what are the different methods for liver biopsy?
u/s guided percutaneous FNA/tru-cut
open surgical technique
laparoscopic technique
what is the advantage of open/laparoscopic liver biopsies?
more accurate
yield a better sample
allows for gross visualisation and examination of the abdominal organs
what are the indications for a partial/complete hepatic lobectomy?
removal of benign/malignant masses, abscess, liver lobe torsion
what are the risks of partial/complete hepatic lobectomy?
haemorrhage
liver failure
portal hypertension
what is cholecystectomy?
removal of the gallbladder
what is cholecystoenterostomy?
rerouting of the gallbladder into the duodenum
what are the indications for cholecystectomy/cholecystoenterostomy?
biliary tract rupture and bile peritonitis
diseases causing extrahepatic biliary tract obstruction e.g. gallbladder mucocele, choleliths, pancreatitis, neoplasia
what are the main perioperative considerations during hepatic surgery?
hypotension - arterial line ideal
hypothermia - often difficulty regulating temperature
significant risk of haemorrhage even if coagulation abnormalities identified and mitigated
IVFT throughout surgery
care with premedication and induction choice - avoid heavy hepatic metabolism
ventilation if facilities available
perioperative abs indicated
what are the post-operative care considerations after hepatic surgery?
intensive nursing required for critical animals
pain scoring and adequate analgesia
monitoring - physical parameters, BP, signs of haemorrhage, bile leakage
minimum database - haem and biochem
abs if infection present
nutrition - prescription liver diet
monitor for sepsis/SIRS
what is a portosystemic shunt?
an anomalous blood vessel which connects the hepatic portal vein with the systemic venous circulation, thereby passing the liver and diverting some of the portal blood supply away from the liver
what can occur as a result of poor liver development due to PSS?
reduced protein production
altered fat and protein metabolism
reticuloendothelial dysfunction
how long should a patient be starved for a bile acid stim test?
at least 12 hours
how long should be left inbetween the pre-prandial and postprandial blood samples in a bile acid stim test?
as close to 2 hours as possible
what diet should be fed to patients with PSS?
highly digestible
high biological value of protein
fatty acids, vitamins and minerals to meet the minimum requirements of the individual
e.g. purina HP, royal canin hepatic, hills l/d
why should patients undergoing corrective PSS surgery be starved for no longer than 8 hours?
due to reduced glycogenolysis and gluconeogenesis reserve
why should patients undergoing corrective PSS surgery have a peripheral and central IVC placed?
peripheral for drug admin and IVFT
central for blood sampling, glucose monitoring
what blood parameter should be measured very regularly/closely during PSS surgery?
blood glucose - predisposition to hypoglycaemia, often paediatric patients
how can we reduce risk of complications due to haemorrhage during PSS surgery?
ascertain clotting times pre-surgery
blood cross matching and correct blood type available for transfusion
why is it advantageous to have access to sympathomimetics during PSS surgery?
hypotension likely unresponsive to fluid therapy
reduced proteins in blood due to impaired liver function means blood has less oncotic pressure - fluids given are rapidly lost to the extravascular space
what should we be monitoring after after the PSS has been occluded?
portal hypertension
what post-operative monitoring is required after PSS surgery?
ideally ICU-level nursing - often not possible
temperature - prone to hypothermia, shivering will use up glucose unnecessarily
blood pressure (15-30 min intervals) - colloids helpful part of IVFT if unresponsive to crystalloids
glucose monitoring every hour until patient awake
pain score hourly, analgese accordingly (no NSAIDs)
which type of drug should be avoided in patients who have had PSS corrective surgery?
NSAIDs - risk of GI ulceration associated with portal hypertension
