Abstract
A 5.5 year old, 32 kg Boxer, suffering a severe heart disease due to a final stage subaortic stenosis and mitral insufficiency, was anaesthetized for an ovariohysterectomy to remove an ovarian tumour that was producing high volume ascites. Methadone (0.3 mg kg-1) was given for premedication, etomidate (1.3 mg kg-1) and midazolam (0.2 mg kg-1) were used for anaesthetic induction and after endotracheal intubation, anaesthesia was maintained with sevoflurane vaporized in oxygen and air. Fentanyl (5-10 μg kg-1 h-1) and paracetamol (15 mg kg-1) were given to improve analgesia. Previous persistent atrial fibrillation was refractory to medication (digoxin, diltiazem and pimobendan) and maintained during the anaesthetic procedure. Dobutamine (1.5-5 µg kg-1 min-1) helped to maintain mean arterial blood pressure above 60 mmHg. Epidural morphine (0.1 mg kg-1) and incisional bupivacaine (2 mg kg-1) were administered at the end of surgery to provide postoperative analgesia. Otherwise, anaesthesia was uneventful, and recovery was considered excellent.

Key words: anaesthesia, atrial fibrillation, dog, mitral, subaortic stenosis