Acute Hyperkalaemia During General Anaesthesia in Two Cows

An 8-year-old, 600 kg, female Simmental cow and a 6-year-old, 662 kg, pregnant Hérens cow were referred for surgical repair of mandibular symphyseal fractures following trauma in two unrelated events. Pre-anaesthetic blood tests revealed mild hypokalaemia in the Simmental cow and mild hypocalcaemia in the Hérens cow. Anaesthesia was induced with xylazine, ketamine, and lidocaine, and maintained with isoflurane combined with a ketamine constant rate infusion. Throughout most of the procedures, physiological parameters remained stable, although mild hypercapnia and progressive bradycardia were noted. During surgical closure, both cows developed sudden severe bradycardia, followed by ventricular escape beats and short periods of asystole. Arterial blood gas analysis revealed acute severe hyperkalaemia, with potassium concentrations of 6.8 mmol/L in the Simmental cow and 8.66 mmol/L in the Hérens cow. Immediate treatment with a calcium–magnesium–glucose solution was initiated, resulting in rapid improvement in heart rate, restoration of sinus rhythm, and reduction in potassium concentrations. Both cows recovered uneventfully, with normal electrolyte values over the following 72 h. This report describes acute intra-anaesthetic hyperkalaemia in two cattle, including a pregnant animal, occurring without an identifiable predisposing factor. Continuous monitoring and rapid recognition of changes in cardiovascular status and electrolyte concentrations allowed prompt treatment and restoration of normal cardiac rhythm.