Clinical Presentations, Treatment, and Outcomes in Patients Who Developed Malignant Hyperthermia (MH) Intraoperatively: A Case Series Study

Objectives: To investigate the clinical presentations, treatment, and outcomes in a large sample of patients who developed malignant hyperthermia (MH) intraoperatively. Background: To our knowledge, no investigations have studied a large sample of patients who developed MH intraoperatively to assess the frequencies of the most common clinical presentations, inciting anesthetics, treatment and patient outcomes. Thus, a case series study of patients who developed MH that focuses on these outcomes may give anesthesia providers critical information regarding risk factors and how to recognize patients who are developing MH early, so that early interventions focused on optimizing clinical outcomes can be implemented. Study Design: A case series. Methods: A review of case studies involving patients who developed MH intraoperatively was conducted. We completed searches using PubMed, Web of Science, and Embase library databases with the search term “Malignant Hyperthermia” for all articles published from August, 2016 - August, 2021. Only studies published in English were included. Two reviewers independently extracted data. Patient demographics and intraoperative measures were reported as frequencies and percentages of the total sample with means and standard deviations. The main outcomes included surgery category, patient outcome, inciting anesthetics, initial patient presentation, and treatment, and were reported as frequencies and percentages of the total sample. Of the 915 initially identified articles, duplicates, studies that were non-accessible, studies that were not case reports, and studies that were not published in English were excluded. The remaining articles were screened for relevance and 69 case studies met the inclusion criteria for evaluation. Microsoft Excel ToolPak was used to organize and compute all reported measures. Results: Of the studies included (n=69), the average age of patients who developed MH was 26 years. The average maximum intraoperative temperature was 39.6C and the average maximum intraoperative blood pressure was 155/88 mmHg. The average time to develop MH among included cases was 122 minutes. 14.5% of the included sample were undergoing cancer surgeries, 14.5% of patients were undergoing cardiac surgeries, 21.7% of patients were undergoing orthopedic surgeries, and 49.3% were undergoing other surgical procedures. The mortality rate from MH was 10.1% among included cases. The most common inciting anesthetics among patients who developed MH were inhaled anesthetics (62.3%) and succinylcholine (13.0%). The most common initial patient presentations at the onset of MH development were hypercapnia (29.0%), tachycardia (20.3%), and pyrexia (10.1%). Among included studies that discussed treatment of patients who developed MH intraoperatively (n=52), some of the most commonly utilized treatment agents included dantrolene (73.1%), external cooling (51.9%), internal cooling (25.0%) and sodium bicarbonate (25.0%). Conclusion: The findings reported in this study, such as intraoperative measures, patient presentation and outcomes, inciting agents, and treatment among patients who developed MH intraoperatively should be considered by anesthesia providers to optimize patient outcomes.