Anesthesia Management in a Patient With a History of Fulminant Malignant Hyperthermia and a Homozygous RYR1 p.Arg530His Variant Undergoing Laparoscopic Surgery: A Case Report.

BACKGROUND Malignant hyperthermia (MH) is a rare but potentially fatal pharmacogenetic disorder triggered by volatile anesthetics or suxamethonium, most commonly associated with variants in the ryanodine receptor type 1 (RYR1) gene. Patients with confirmed or suspected MH susceptibility are advised to avoid triggering agents and undergo regional anesthesia or total intravenous anesthesia (TIVA). Remimazolam, an ultra-short-acting benzodiazepine approved in Japan for general anesthesia, has been shown in vitro not to increase intracellular calcium concentrations in cells expressing MH-associated RYR1 variants. However, clinical evidence regarding its safety in genetically confirmed MH remains limited. CASE REPORT An 80-year-old man with a history of fulminant MH at age 39, successfully treated with dantrolene, was scheduled for laparoscopic inguinal hernia repair. Previous calcium-induced calcium release testing confirmed MH susceptibility. Genetic analysis revealed homozygosity for the RYR1 c.1589G>A (p.Arg530His) variant, classified as likely pathogenic. Given his history and cardiovascular comorbidities, remimazolam-based TIVA was selected. Anesthesia was induced and maintained with remimazolam, remifentanil, and rocuronium under strict MH precautions, including immediate availability of dantrolene. Intraoperative end-tidal carbon dioxide, core temperature, and hemodynamics remained stable, with no signs of MH. Neuromuscular blockade was reversed with sugammadex, and recovery was uneventful without postoperative complications. CONCLUSIONS Remimazolam-based TIVA was successfully administered in a patient with genetically confirmed MH susceptibility carrying a homozygous likely pathogenic RYR1 variant. The perioperative course was uneventful, suggesting that remimazolam-based TIVA may be a feasible anesthetic approach in selected high-risk MH-susceptible patients, including those with severe prior episodes and significant cardiovascular comorbidities.