Generalised tetanus in a cat successfully treated with magnesium sulphate and dexmedetomidine

A 4‐year‐old, neutered male domestic short‐haired cat was presented with an abdominal injury, severe extensor rigidity of all limbs and sardonic facial expression. The cat was diagnosed with tetanus and antibiotics, and antiemetics and analgesics were administered. In order to provide myorelaxation, in addition to midazolam, a supraphysiologic dose of magnesium sulphate was infused intravenously at a constant rate of 10 mg/kg/h, after a loading dose of 70 mg/kg; serum magnesium and ionic calcium were measured daily. During hospitalisation, the cat showed hypersensitivity to stimuli, tetanic seizures, hyperthermia and autonomic dysfunction, presenting as severe hypertension, sinus and ventricular tachycardia. An intravenous infusion of dexmedetomidine (1 ± 0.5 µg/kg/h) improved haemodynamic parameters and attenuated muscle spasms, and its administration was continued for 96 h without adverse reactions. The magnesium infusion was maintained for 11 days without toxicity, except for a mild hypocalcaemia. The cat's clinical signs gradually improved and the patient was discharged on day 28.