Liver disease

Classification system to assess risk:

• Ascites
• Encephalopathy
• Bilirubin
• Albumin
• Prothrombin time

Pharmacokinetics

Distribution:

• Decreased albumin levels – decreased protein binding and therefore increased free drug e.g. thiopentone
• Unbound portion is able to distribute widely; therefore the Vd increases

Detoxification: decreased hepatic clearance of drugs (benzodiazepines and opioids)

Elimination: decreased biliary excretion

Other problems

• Ascites: fall in functional reserve capacity
• Coagulopathy: decreased production of vitamin K-dependent clotting factors (II,VII,IX,X) and non-vitamin K-dependent clotting factors (V,XI,XII,XIII) and altered platelet function
• Renal: hepatorenal syndrome and acute tubular necrosis. Increased plasma volume
• Cardiovascular: high cardiac output and low systemic vascular resistance (severe)
• RS:V/Q mismatch reduces PaO₂

Metabolic: hypoglycaemia and sodium retention

Neurology: encephalopathy

Drugs: corticosteroids

Assessment

• Optimise condition by hepatologist
• May take several weeks (esp. nutrition)
• Full blood count, urea & electrolytes, clotting, liver function tests, glucose, arterial blood gases
• ECG, chest X-ray and hepatitis B status
• Vitamin K and mannitol may be needed preoperatively

Conduct

• Monitoring: Central venous pressure, arterial, capnography, urine output, temperature, nerve stimulator, pulmonary artery wedge pressure if severe myocardial abnormalities
• Regional?? Best option
• General; lower doses required: increased volume of distribution
• Careful titration
• Atracurium thiopentone and isoflurane
• Increased FiO₂ and careful fluid balance
• Perioperative mannitol to maintain urine output
• Avoid lactate and Na fluids, give 5% dextrose
• Warm

Postoperatively

• ITU may be required
• Accurate fluid balance
• Analgesia, carefully
• Risk of infection: prophylactic antibiotics