You have a patient who is to be administered an anesthetic. Might the patient have certain characteristics that would make you think the patient has malignant hyperthermia (MH)? Are there specific clinical signs that help you confirm the diagnosis? Finally, once it’s apparent the patient does have MH, is there a set of characteristics that would help you predict outcome? Drs. Priscilla Nelson and Ronald S. Litman, Department of Anesthesiology and Critical Care, The Children’s Hospital of Philadelphia, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA retrospectively analyzed the North American Malignant Hyperthermia Registry using patients whose MH clinical grading scale score was ≥35, pointing to “very likely” or “ almost certain” MH. Patients were divided into age groups of 0-24 months, 25 months to 12 years, and 13 to 18 years. The authors examined preoperative patient demographics and risk factors, clinical characteristics of the acute MH event, and post-event clinical characteristics and outcomes. Their results are published in this month’s issue of Anesthesia & Analgesia in the article titled “Malignant Hyperthermia in Children: An Analysis of the North American Malignant Hyperthermia Registry.”
Quite a bit of information concerning patient demographics and procedural characteristics is contained in the article’s table 1. Significant characteristics include male gender, surgery for inguinal hernia (more common in the youngest age group), undescended testicles (more common in the youngest age group), dental procedures, otolaryngology procedures (about 40% of the events in the middle age group), general surgery, orthopedic surgery (50% of the oldest age group’s events), urology (almost 30% of events in the youngest age group), elective procedures (adolescents had a higher percentage of emergent procedures), and patients for whom an intravenous induction was performed (patients in the youngest age group were more likely to have inhalation induction; intravenous induction was more common for emergent cases). The youngest age group was less likely to receive IV succinylcholine, vecuronium, propofol, or fentanyl but was more likely to receive halothane or sevoflurane compared to the older patients. Significant physical findings and laboratory values, summarized more completely in the article’s table 2, include rapidly increasing temperature, sweating, masseter spasm, hypercarbia, sinus tachycardia, maximum temperature, time to maximum temperature, maximum end-tidal CO2, time to maximal end-tidal CO2, CO2, PO2, peak lactic acid, peak potassium, and peak creatinine kinase. Significant treatment and outcomes, summarized in the article’s table 3, include active cooling, fluid loading, glucose/insulin, dantrolene side effects, and hyperkalemia or muscle weakness secondary to dantrolene. Dantrolene was used in almost 75% of events.
Generally, older children had more severe effects of MH than younger patients. They were more likely to develop a rapidly increasing temperature, a higher maximum temperature, higher potassium levels, and higher peak creatine kinase levels. This speaks to greater degrees of rhabdomyolysis, which makes sense given that older children have more muscle mass than younger children.
The report concludes that there is no definitive MH phenotype.