title: Malignant hyperthermia in Canada: characteristics of index anesthetics in 129 malignant hyperthermia susceptible probands.
abstract: BACKGROUND
  Between 1992 and 2011, 373 Canadian individuals with adverse anesthetic reaction were referred to the Malignant Hyperthermia Unit in Toronto, Ontario, Canada for malignant hyperthermia (MH) diagnostic testing. We analyzed the epidemiologic characteristics of the index adverse anesthetics for those probands who were confirmed to be MH susceptible.
  
  
  METHODS
  One hundred twenty-nine proband survivors of adverse anesthetic reactions, whose MH susceptible status was confirmed by caffeine-halothane contracture testing were selected. Individuals were excluded if the index anesthetic record was not available for review. Data regarding demographics, clinical signs, laboratory findings, treatment, and complications were retrospectively compiled and analyzed. A Fisher exact test and χ test were applied to compare categorical variables. The Wilcoxon rank-sum test was applied with continuous variables.
  
  
  RESULTS
  Young males (61.2%) dominated among selected patients. Seventeen of 129 (13.2%) patients had prior unremarkable anesthesia. Anesthetic triggers were volatile-only (n = 58), succinylcholine-only (n = 20), or both volatile and succinylcholine (n = 51). Eight (6.2%) cases occurred in the postanesthetic care unit. There were no reactions after discharge from the postanesthetic care unit. The most frequent clinical signs were hyperthermia (66.7%), sinus tachycardia (62.0%), and hypercarbia (51.9%). Complications occurred in 20.1% of patients, the most common complication being renal dysfunction. When 20 or more minutes between the first adverse sign and dantrolene treatment elapsed, complication rates increased to ≥30%.
  
  
  CONCLUSIONS
  This is the first Canadian study in 3 decades to report nationwide data on MH epidemiology. Features that differ from earlier reports include a 15.5% incidence of reactions triggered by succinylcholine alone and lower complication rates. In agreement with previously published studies, we confirmed in this independent dataset that increased complication rates were associated with an increased time interval between the first adverse clinical sign and dantrolene treatment. This underscores the need for early diagnosis and rapid dantrolene access and administration in anesthetizing locations using either succinylcholine or volatile anesthetic drugs.
authors.affiliation: From the Malignant Hyperthermia Investigation Unit, Toronto General Hospital, University Health Network; Department of Anesthesia, University of Toronto, Toronto, Ontario, Canada; The North American Malignant Hyperthermia Registry of the Malignant Hyperthermia Association of the United States, Pittsburgh, Pennsylvania; and Toronto, Ontario, Canada.
authors.forename: Sheila
authors.initials: S
authors.lastname: Riazi
authors.forename: Marilyn Green
authors.initials: MG
authors.lastname: Larach
authors.forename: Charles
authors.initials: C
authors.lastname: Hu
authors.forename: Duminda
authors.initials: D
authors.lastname: Wijeysundera
authors.forename: Christine
authors.initials: C
authors.lastname: Massey
authors.forename: Natalia
authors.initials: N
authors.lastname: Kraeva
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000777:Anesthetics / Q000009:adverse effects*; D002110:Caffeine / Q000009:adverse effects; D002170:Canada; D002648:Child; D002675:Child, Preschool; D003620:Dantrolene / Q000009:adverse effects / Q000627:therapeutic use; D005260:Female; D005334:Fever / Q000175:diagnosis; D006221:Halothane / Q000009:adverse effects; D006801:Humans; D006935:Hypercapnia / Q000175:diagnosis; D015994:Incidence; D007223:Infant; D008297:Male; D008305:Malignant Hyperthermia / Q000453:epidemiology* / Q000209:etiology*; D008875:Middle Aged; D009154:Mutation; D012042:Registries; D012189:Retrospective Studies; D019837:Ryanodine Receptor Calcium Release Channel / Q000235:genetics; D013390:Succinylcholine / Q000737:chemistry; D013610:Tachycardia / Q000175:diagnosis; D055815:Young Adult
chemical_list: D000777:Anesthetics; D019837:Ryanodine Receptor Calcium Release Channel; D002110:Caffeine; D003620:Dantrolene; D013390:Succinylcholine; D006221:Halothane