Final FRCA – Medicine for the FRCALaura Dyal

ST6 Anaesthetics

8/5/2019

The Liver….

Learning plan

• Revise basic physiology of Liver

• Causes of Liver failure

• Acute

• Chronic

• Systemic effects of Chronic Liver disease

• Anaesthetic implications

• Acute Liver failure

• Exam practice

Liver MCQ – T/F

• The liver is one of the largest organs in the human body and undertakes multiple tasks. Regarding Liver function:

a. 70% of liver blood flow is via the hepatic artery

b. Portal tracts contain lymphatics

c. Plasma cholinesterase is produced by the liver

d. Vitamin E is stored in the Liver

e. Plasma concentrations of alanine aminotransferase increases in normal pregnancy

Anatomy of the Liver

Functional anatomy - Liver

• Bile ducts• Hepatic artery• Portal vein• Vagus nerve • Lymphatics

Functions of the Liver

1. Synthesis

2. Metabolism

3. Storage

4. Catabolism and excretion

5. Immunological / Haematological

1. Synthesis

• Proteins

• Albumin (200mg/kg/day!)

• Clotting factors

• Transport globulins

• Complement

• Plasma cholinesterase

• Alpha 1 antitrypsin

• Fats

• Triglycerides

• Cholesterol

• Bile

2. Metabolism

• Glucose homeostatis

• Glycogen synthesis and storage

• Gluconeogenesis

• Absorbs other nutrients

3. Sto

rage

Glycogen Iron

Copper

DA

EK

FOLATE

B12

4. Catabolism and excretion

• Drug metabolism

• Detoxification

• Phase 1 reactions (cytochrome P450)

• Phase 2 reactions

• First pass metabolism

• Excretion:

• Nitrogenous waste - Urea cycle

• Haem metabolism - Bilirubin

5. Immunological and Haematological• Kupffer cells – (fixed macrophages)

• Hepatocytes make

• Fibrinogen

• Heparin

• Prothrombin

Answers to MCQ

a. 70% of liver blood flow is via the hepatic artery False – 20-30% of cardiac output goes to the liver. 70% from portal vein and 30% from hepatic artery

b. Portal tracts contain lymphatics True – lymphatics and branch of vagus nerve travel with the hepatic artery, bile ducts and portal vein in portal tract

c. Plasma cholinesterase is produced by the liver True – plasma cholinesterase is synthesised by the liver

d. Vitamin E is stored in the Liver True – Vitamin E is stored

e. Plasma concentrations of alanine aminotransferase increases in normal pregnancy False – ALP increase up to 4x but ALT and AST and LDH generally do not increase.

The relevance to exams – from personal experience….12/3/15!

Liver failure

Chronic

• Viral • Hepatitis B and C

• Alcoholic Liver Disease

• Autoimmune

• Cryptogenic

• Cholestatic-• Primary billary cirrhorhosis

• -Sclerosing Cholangitis

• Venous outflow obstruction• Budd Chairi syndrome

• Metabolic • Wilsons Disease

Chronic Liver failure – systemic effects• Group work

1. Respiratory

2. Cardiovascular

3. Heamatological

4. Neurological

5. Gastrointestinal

The effects of liver disease: GI

Cardiovascular effects

• Hyperdynamic circulation

• Risk factors for IHD

• Smoking

• Hyperlipidemea

• Reduced LV workload

• Decreased SVR

• Vasodilatation

- May mask coronary artery disease

Hyperdynamic circulation in liver disease

Respiratory system

• Diaphragmatic splinting

• Hepatopulmonary syndrome

• V/Q mismatch caused by intrapulmonary shunting

• Portopulmonary syndrome (rare)

• Pulmonary hypertension due to progressive pulmonary vasoconstriction

• Remodelling causes increase PVR

Haematological

II, VII, IX, X

Increased fibrinolysis

Renal / Metabolic

• Secondary hyperaldosteronism

• Water retention

• Hyponatremia

• Treated with spironolactone (risk of hyperkalemia)

• Hepatorenal syndrome

• Renal hypoperfusion, portal hypertension, Intrabdominal hypertension (poor prognosis)

• Hypoglycemia

Neurological

• Hepatic encephalopathy increased by:

• Infection

• GI Haemorrhage

• Acid base disturbance

• Sedative drugs

• Hypoglycaemia

• Hypoxia

• Hypotension

• Excessive dietry protein

• ALD –

• risk of Vitamin B1 deficiency and Wernicke's encephalopathy

Questions so far?

Long case prep sheet

Summary of case Current investigations –what do they show?

Pharmacology:

1. Drugs on an effects 2. Drugs to consider

that may have issues3. Drugs to avoid

Pre operaitve

• Any more inforequired?

• Any more investigations required

• Preoptimisation

Intra operative

• Pre-induction• Induction• Airway management • Analgesia • Maintenance • Temperature

regulation• Specifics for this case

Post operative

• Post op destination (ward/HDU/ICU)

• Thromboprophylaxisis• Analgesia• Extras: eg chest

physio

Anaesthetic Implications –Group work • Pharmacology

• Pharmacology headlines in liver failure

• Specific drugs

• Induction agents

• Volitiles

• NMBD

• Opiods

• Pre-optimisation and investigations

• Intraoperative considerations

• Post operative care

Pharmacology in Liver disease

• Reduced plasma proteins

• Increased unbound fraction of protein bound drugs

• Increased distribution half life

• Increased duration of action

• Increased Volume of distribution

• Reduced metabolism

• Phase 1 reactions generally affected before phase 2 reactions

• Reduced elimination

Pharmacology Drug class Effects of liver failure Anaesthetic modifications

Induction agents

• Reduced plasma proteins -increased unbound fraction of protein bound drug

• Increased duration of action • More sensitive to sedative effects

of propofol

• Reduce dose of thiopentone• Reduce dose of propofol

(Chronic alcohol use may require higher doses of induction agent- but with

Volatileagents

Iso, sevo and des undergo minimal hepatic metabolism

Can all drop CO and MAP. Des has least hepatic metabolism and quickest emergence

Opioids • Elimination of morphine delayed • Accumulation of morphine-6-

glucuronide will occur in those with associated renal failure

• Alfentanly elimination delayed

• Remifentanyl safe• Low dose fentanyl good • Avoid morphine and

allfentanyl if possibe

NMBDs Reduced plasma cholinesterasesIncreased volume of distributionReduced protein binding Prolonged elimination (Vec /Roc)

• Metabolism of sux increased • Resistance to NMBDs • Use Cis/Atracurium

preferably

Pre-op/optimisation

• History /Examination • Check for pleural effusions/ascites

• Level of encephalopathy

Think about effects other than patient – risk of infection (viral hepatitis)

Investigations

Investigation Possible effects of Liver disease

FBC Decreased PlateletsAnaemiaIncreased MCV ( Alcohol / vit B12 def)

Clotting PT – useful indicator of hepatocellular failure

U+Es HyponateaemiaCheck for renal dysfunction

ECG If risk factors LV dysfunction

CXR Check for pleural effusions

Echocardiogram Check for underlying cardiomyopathy

Risk Stratification

Score Operative mortality risk (%)

5-6 Childs class A = low operative risk (5%)

7-9 Childs class B = Moderate risk (25%)

10-15 Childs class C = High operative risk (50%)

Intraoperative

• Elective surgery - only for well compensate chronic liver failure

• Emergency surgery – patients need urgent optimisation to include: • Intra vascular volume status

• Coagulation function

• Neurlogical assessment

• Screening for infection

• Consider blood products• PT>1.5

• Platlets <50

Intra op continued

• Induction: • Modified RSI• Propofol ( reduced dose) • Give H2 receptor blocker pre induction

• Analgesia • Remifentanil, low dose fentanyl• Avoid morphine and alfentanil

• Monitoring: (Maintaining MAP is important)• A line • CVP line • Oesophageal doppler (contraindicated?)

• Maintentence• Desflurane• Atracurium or Cis-atracurium

• IV fluids: • Crystalloids • Consider HAS in ascitic patients • Background infusion of 5-10% Dextrose to avoid hypoglycaemia

Post Operative

• Anticipate ICU/HDU requirement

• Invasive cardiac monitoring

• Careful fluid management

• Look out for

• Worsening encephlopathy

• Worsening jaundice

• Check clotting regularly

• Analgesia

• IV fentanyl PCA

Questions?

TIPS procedure

SBA 1

• You are asked to anaesthetize a 34-year-old lady for insertion of a transjugular intrahepatic porto-systemic shunt. She is suffering from Budd–Chiari syndrome and has large tense ascites. She has no other past medical history and gives no history of reflux. The procedure has been attempted twice under local anaesthesia, but she was unable to tolerate the procedure due to discomfort. Your anaesthetic plan is to:

a. Ask the physicians and radiologists to attempt the procedure under local anaesthesia again, with larger volumes of local anaesthetic

b. Ask the physicians to improve her respiratory function by draining the ascites first

c. Ask the physicians to perform the procedure again with sedation d. Provide regional anaesthesia with a cervical plexus block, a large iv

access, invasive arterial monitoring and cardiovascular stability, with blood products available

e. Provide general anaesthesia with an ETT, a large iv access, invasive arterial monitoring and cardiovascular stability, with blood products available

SBA 1 answer

• Answer: e

It is unlikely that they will succeed with local anaesthesia if they have tried twice before and it is unfair to the patient if she finds it distressing or uncomfortable. The question states the procedure was terminated twice due to discomfort, not hypoxia. However, this does have to be borne in mind for people with large, tense ascites. Sedation is an option, but the potential for the respiratory depressant effects of sedation on patients with liver disease with pulmonary dysfunction (from ascites or porto-pulmonary associations), as well as their prolonged action of sedative drugs, the risk of aspiration, the risk of precipitating encephalopathy and a prolonged procedure make a general anaesthetic with a secure airway the treatment of choice.

Acute Liver Failure

• SBA

• Definitions

• Multisystem effects

• Transplant criteria ( Kings College Criteria)

SBA 1

• The incidence and prevalence of liver disease is increasing worldwide. What is the most common cause of acute hepatic failure in the UK?

a. Ethanolb. 3, 4-methylenedioxymethamphetaminec. Amanita phalloides

d. Viral hepatitis

e. Acetaminophen

SBA 1 Answer = E

In the UK acetaminophen overdose is the most common cause of acute hepatic failure (70%) while worldwide it is viral hepatitis. Alcohol and other drugs are implicated while Amanita phalloides is a poisonous mushroom and a rare cause of acute hepatic failure.

Acute Liver Failure

• Acute liver failure (ALF) is a devastating syndrome that triggers a cascade of events, leading to multiple organ failure and often death.

• In those patients with high grades of encephalopathy, the chances of survival are less than 20% with medical management alone.

• Early deaths: cerebral oedema or cardiovascular collapse• Late deaths: sepsis and multiple organ failure • Liver transplantation is the only current definitive

treatment in those failing supportive medical management.

Acute Liver failure Classification• ALF – syndrome defined by the occurrence of encephalopathy,

coagulopathy and jaundice in an individual with a previously normal liver.

• Hypeeracute – within 7 days

• Acute – 8-28 days

• Subacute – 5-26 weeks

Liver failure

Chronic

• Viral • Hepatitis B and C

• Alcoholic Liver Disease

• Autoimmune

• Cryptogenic

• Cholestatic-• Primary billary cirrhorhosis

• -Sclerosing Cholangitis

• Venous outflow obstruction• Budd Chairi syndrome

• Metabolic • Wilsons Disease

Acute

• Paracetamol overdose

• Viral hepatitis

• Circulatory shock

• Drugs• Aspirin

• Rifampicin

• Acute fatty liver of pregnancy

Systemic effects –Neuro

• Encephalopathy

• Mortality higher in those with Grade III or IV

• Cerebral oedema

• In up to 80%

• More in hyperacute ALF

• Raised ICP

Systems effects – CVS

• Similar picture to sepsis

• Hypotension

• Low SVR

• High Cardiac output

Systemic effects - Renal

• Oliguric renal failure

• Occurs in 75% of paracetamol overdose patients

• 30-50% in other causes

• Usually indicator of poor prognosis

Systemic effect – Immune

• Decreased complement synthesis

• Kuffer cell dysfunction

• Increased suseptibility to infection

• Increased risk of fungal infections

Kings Criteria

References

• Vaja R (2010) Anaesthesia for patients with liver failure, Continuing Education in Anaesthesia, Critical Care & Pain | Volume 10 Number 1, BJA, oxford University Press

• Lai et al, (2004),Management of Acut Liver failure Continuing Education in Anaesthesia, Critical Care & Pain | Volume 4, Issue 2 April 2004 Pags 40-43

• Ebrahim et al (2013) (Practice Single Bset Anser questions for the Final FRCA – A revision guide. Cambrige Univerisyt Press,P65 and 132