Sedation and general anaesthesia may be required in animals with confirmed or suspected portosystemic shunt for a variety of reasons, not limited to shunt attenuation, such as diagnostic, routine or emergency procedures. Veterinary surgeons should understand normal hepatic functions and processes in order to appreciate the implications of portosystemic shunts associated specifically with sedation and anaesthesia. The pathophysiological and physiological variations, and their effects on anaesthesia and sedation, are discussed, as is management of the peri-anaesthetic period, drug choice for sedation or premedication, induction and maintenance of anaesthesia and analgesia. Patient monitoring and problem solving are also discussed, in relation to situations commonly encountered in portosystemic shunt patients during anaesthesia and sedation.

A 16-month-old cocker spaniel, body mass 15 kg, was presented for general anaesthesia for thoracotomy and lung lobectomy. Preanaesthetic medication was with intramuscular medetomidine (0.01 mg/kg) and methadone (0.2 mg/kg). General anaesthesia was induced with propofol and maintained with propofol and ketamine infusions. A single thoracic epidural injection with levobupivacaine (0.5%, 1 mg/kg) and morphine (0.1 mg/kg) at the 12th-13th thoracic intervertebral space was performed. Postoperative analgesia was with one intravenous dose of methadone (0.2 mg/kg), levobupivacaine (1 mg/kg) via indwelling thoracostomy tube and intravenous paracetamol (10 mg/kg) every 8 hours, and meloxicam (0.1 mg/kg) orally every 24 hours. Pain scoring (Glasgow CMPS-SF) was carried out every 4 hours until 1 hour after removal of the thoracostomy tube, never exceeding 2/24. No further opioid analgesics were administered and the patient was discharged with no complications.

A male, estimated body mass 60 kg, six‐month‐old Gloucester Old Spot pig was anaesthetised, and the trachea intubated for repair of a large umbilical hernia. Following endotracheal intubation and connection to the anaesthetic breathing circuit and machine, cyanosis was noted, and hypoxaemia, with hypercapnia, was later confirmed by arterial blood gas analysis. Differentials for hypoxaemia under general anaesthesia include inadequate delivery of oxygen, hypoventilation, ventilation: perfusion (V:Q) mismatching, diffusion disorders and intrapulmonary shunting. Hypoxaemia was eventually resolved by repositioning of the endotracheal tube, and the remainder of the anaesthesia, surgery and recovery were uneventful. Swine possess a tracheal bronchus which supplies, most usually, the right cranial lung lobe, and the practitioner should be aware of its presence and of the consequences of inadvertent intubation, bypass or blockage of the bronchus of this cranial lung lobe, as well as methods to avoid this complication.

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