• Elena Zvaritch, Robyn Gillies, Natalia Kraeva, Maxime Richer, Heinz Jungbluth, and Sheila Riazi.
• Malignant Hyperthermia Investigation Unit, Toronto General Hospital, 323-200 Elizabeth Street, Toronto, ON, M5G 2C4, Canada.
• Can J Anaesth. 2019 May 1; 66 (5): 540-545.

PurposeThe present report of two fatal awake malignant hyperthermia (MH) episodes in an MH susceptible (MHS) family is intended to raise awareness among medical personnel and MHS individuals to the possibility of life-threatening non-anesthesia-triggered MH episodes and to provide a strong incentive for development of effective preventive measures.Clinical FeaturesTwo young athletic males (28 and 16 yr old), members of the same extended family with a history of anesthesia-related MH episodes and deaths, succumbed ten years apart on two different continents, with symptoms unrelated to anesthesia but strikingly similar to typical anesthetic-induced MH. Both suffered an abrupt surge in body temperature, tachycardia, tachypnea, muscle rigidity, hyperkalemia, and respiratory and metabolic acidosis. Despite aggressive resuscitation attempts, both developed cardiac arrest and died shortly upon arrival to hospital emergency departments. Autopsy analyses were negative for drugs, alcohol, or bacterial infection. Individual and familial genetic analyses revealed a novel, potentially pathogenic RYR1 variant (p.Gly159Arg) that co-segregates with the MHS phenotype in the family. Both fatal awake MH episodes are hypothesized to have been triggered by physical exertion compounded with a febrile illness that in one case was due to influenza type A.ConclusionsLife-threatening awake MH episodes may develop in some MHS individuals in the absence of anesthetic triggers. Potential triggers can be physical exertion in combination with a febrile illness. Malignant hyperthermia susceptible patients are recommended to be vaccinated against flu and restrict physical activities when febrile, wear an MH alert bracelet, and inform medical personnel of their MH history. Oral dantrolene is suggested to be available to MHS patients for administration with the early signs of awake MH.

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