Analysis of the clinical variables associated with recrudescence after malignant hyperthermia reactions

Background: Some patients develop recrudescence after a malignant hyperthermia (MH) reaction, but it is not clear which patients are at risk. The authors analyzed clinical variables associated with recrudescence after a clinical MH episode. Methods: Data were obtained from Adverse Metabolic Reaction to Anesthesia reports in the North American Malignant Hyperthermia Registry. Patients who underwent general anesthesia and with an MH clinical grading score of 20 or greater, indicating a likely MH reaction, were included in this analysis. Patient characteristics, anesthetic agents, MH reaction clinical details, and postoperative outcomes were compared in the recrudescence and no recrudescence groups using chi-square tests and Z tests for categorical variables and the Student t test for continuous variables. Associations of clinical variables with recrudescence were assessed with univariate and multivariate logistic regression. Results: Of 308 patients, 63 (20%) had recrudescence. The mean time from initial reaction to recrudescence was 13 h (SD = 13 h). Patients with recrudescence were more likely to have a muscular body type (P < 0.01), malignant hyperthermia score of 35 or greater (P < 0.01), a temperature increase (P < 0.01), and more than 150 min from induction to adverse reaction (P < 0.05). Muscular body type, a temperature increase, and a longer time from induction to initial malignant hyperthermia reaction were associated with recrudescence on multivariate logistic regression analysis. Conclusions: Recrudescence occurred in 20% of patients. Muscular body types had a higher rate of recrudescence, perhaps associated with increased muscle mass. The risk of recrudescence increased as time from induction to the initial MH reaction increased, perhaps as a result of greater muscle exposure to triggering agents.