Analysis of anaesthesia in patients suspected to be susceptible to malignant hyperthermia before diagnostic in vitro contracture test

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Abstract
Background: It is well known that patients susceptible to malignant hyperthermia (MH) do not always develop clinical signs of MH at their first anaesthetic. Large material concerning this epidemiological problem do not exist. Therefore, we undertook the present investigation at the Danish Malignant Hyperthermia Register. Methods: Retrospective analysis of anaesthetics given to 371 patients before in vitro contracture test (IVCT) for susceptibility to MH or before death of MH. Patients (or relatives in the case of a dead patient) gave information about previous anaesthetics and anaesthetic charts were collected and reviewed. Results: Fifteen patients died of clinical MH, 112 patients survived an episode of suspected MH, and 244 patients were relatives of the above. Of the 127 patients with clinical signs of MH, 37% had received anaesthesia before, and trigger agents (potent inhalational agents and /or suxamethonium) were used in 98% of patients with no statistical difference between MH‐susceptible (MHS) and non‐susceptible (MHN) patients. Emergency anaesthesia was more frequent in patients with fulminant MH compared to those with abortive forms of MH (P< 0.01). Of the 244 relatives, 48% had received anaesthesia before MH was suspected in the family and trigger agents were used in 44% of the anaesthetics without statistical difference between MHS and MHN relatives. In 17 cases, trigger agents were used for anaesthesia after MH was suspected in the family, but before IVCT. Conclusion: The clinical expressivity of the MHS phenotype was found to be 34%‐54%.