Postanaesthetic pulmonary oedema in a dog following intravenous naloxone administration after upper airway surgery

A cavalier King Charles spaniel was anaesthetised for upper airway surgery. A constant rate infusion of fentanyl at 6 μg/kg/hour and top-up boluses (5 μg/kg in total) were used for intraoperative analgesia. Intermittent positive pressure ventilation (IPPV) was instituted due to tachypnoea and inability to maintain normocapnia. Apnoea and severe hypercapnia developed after cessation of IPPV. IPPV was recommenced for 10 min to reduce hypercapnia, after which spontaneous ventilation returned. The patient had not awakened 45 minutes after isoflurane was turned off and 0.01 mg/kg naloxone was administered intravenously due to suspected fentanylinduced narcosis. Following immediate arousal, the patient vomited and suddenly developed symptoms and radiographic changes consistent with pulmonary oedema. General anaesthesia was reinduced and 1 mg/ kg furosemide was administered intravenously. IPPV was started with application of positive end expiratory pressure in an air/oxygen mixture for 60 minutes. Recovery was uneventful. This is the first report of a dog developing pulmonary oedema following intravenous naloxone