A case of suspected malignant hyperthermia in a dog

A 9-month-old, intact male Siberian husky mixed-breed dog weighing 14.7 kg was referred because of right hind-limb lameness. A right femoral head ostectomy was performed. The dog was premedicated with intravenous (IV) dexmedetomidine and methadone. Anesthesia was induced with IV ketamine and propofol and maintained with isoflurane in oxygen delivered through a rebreathing circuit. Two hours after inhalant anesthesia was started, hyperthermia, hypercapnia, tachypnea, and tachycardia were observed. An acute malignant hyperthermia (MH) crisis was suspected. Isoflurane was discontinued and a propofol total IV anesthesia was started, minute ventilation was increased, active cooling was implemented, and IV dantrolene was administered. The dog remained stable overnight and was discharged on the following day. Six weeks later, the dog was anesthetized for femoral head ostectomy revision and to be neutered. A propofol total IV anesthesia protocol was implemented and O₂ was supplied using a T-piece breathing circuit connected to an O₂ tank. Anesthesia was unremarkable and the dog recovered uneventfully. In dogs, MH is a life-threatening emergency caused by an autosomal dominant mutation in the ryanodine receptor 1 gene. All dogs exposed to a triggering agent are at potential risk. An unexpected tachycardia and hypercapnia despite appropriate minute ventilation, as well as exclusion of other causes, should lead clinicians to suspect MH and initiate treatment. Discontinuing the triggering agent and administering dantrolene can help control the hypermetabolic reaction. Key clinical message: This report describes a case in which an acute MH crisis was suspected in a dog during inhalant anesthesia.