Successful cardiopulmonary resuscitation after suspected mandibulocardiac reflex in a Jersey cow.

General anaesthesia in cattle is associated with species-specific risks, while published data on anaesthesia-related morbidity, mortality, and cardiopulmonary resuscitation are sparse. This case report describes an intra-anaesthetic bradycardic cardiac arrest and resuscitation in a 17-month-old female Jersey cow scheduled for osteosynthesis of a right-sided mandibular fracture. Premedication consisted of xylazine [0.1 mg kg-1 intramuscularly (IM) and 0.03 mg kg-1 intravenously (IV)], butorphanol (0.05 mg kg-1 IV), meloxicam (0.5 mg kg-1 IV), and amoxicillin (10 mg kg-1 IV). General anaesthesia was induced with ketamine (3 mg kg-1 IV), maintained with isoflurane [end-tidal concentration (FE´Iso) 0.9%-1.3% in 100% oxygen], supplemented with a ketamine constant rate infusion (0.5 mg kg-1 hour-1 IV), and mandibular nerve block (lidocaine 0.45 mg kg-1). Thirty-eight minutes after induction and 18 minutes after regional anaesthesia, during percutaneous needle placement along the mandibular fracture line, the cow developed sinoatrial block with ventricular escape rhythm and subsequent episodes of sinus tachycardia with hypertension. Following that, profound bradycardia progressed to cardiac arrest. Cardiopulmonary resuscitation (CPR) was initiated and included external chest compressions, controlled ventilation, and IV injections of epinephrine (0.01 mg kg-1) and atropine (0.01 mg kg-1). Return of spontaneous circulation occurred after three CPR cycles, followed by ventricular tachycardia, which was successfully treated with lidocaine (2 mg kg-1, over 10 minutes). An arterial blood sample analysed at the time of the initial cardiovascular event, but evaluated retrospectively, revealed marked hyperkalaemia (8.1 mmol L-1). Recovery from anaesthesia was uneventful, with no postanaesthetic abnormalities observed. This case suggests that, despite regional anaesthesia, activation of a mandibulocardiac reflex during minor mandibular manipulation, combined with temporary hyperkalaemia, may precipitate cardiovascular collapse. In adult cattle, prompt and structured CPR may be effective if cardiac arrest is rapidly diagnosed and immediate intervention is undertaken.