Severe bradycardia and asystole in a dog after intravenous metoclopramide injection.

A 5-month-old English Bulldog with a history of clinically resolved bronchopneumonia was admitted for a computed tomography scan and corrective surgery for brachycephalic obstructive airway syndrome. The day of imaging and surgery, the dog did not show any signs of cardiovascular abnormalities. The dog was premedicated intravenously (IV) with maropitant (1 mg kg-1), pantoprazole (1 mg kg-1) and acepromazine (20 μg kg-1). Anaesthesia was induced with alfaxalone (2 mg kg-1) IV after 5 minutes of preoxygenation, and anaesthesia was maintained with isoflurane in oxygen [inspired fraction (FIO2) =1]. After induction, physiological variables were unremarkable. Metoclopramide (1 mg kg-1) was injected slowly IV, and the dog immediately developed a severe sinus bradycardia (4 beats minute-1) followed by asystole. Cardiopulmonary resuscitation was started along with atropine (40 μg kg-1 IV), and isoflurane discontinued. Within 1 minute, spontaneous circulation with stable haemodynamic variables was restored. Both the diagnostic and the surgical procedures were completed without further complications. The dog recovered and was discharged the same day. Rare but serious cardiac effects have been described following metoclopramide administration in humans, including bradycardia, asystole and arrhythmia. Cardiotoxicity may be linked to its clinical ability to inhibit sodium channels. To our knowledge, no metoclopramide-induced asystole has previously been reported in veterinary patients. The link between cardiac arrest and metoclopramide administration and possible predisposing factors in this case are discussed.