In malignant hyperthermia-susceptible patients, which medication must be readily available as a precaution?

• A. Dantrolene
• B. Epinephrine
• C. Naloxone
• D. Flumazenil

Answer: (B)

The key idea is that malignant hyperthermia has a specific, treatable crisis, so the team must have an antidote immediately available. Dantrolene is the drug that directly counters malignant hyperthermia by blocking calcium release from the skeletal muscle's sarcoplasmic reticulum via the ryanodine receptor. This halts the runaway hypermetabolic process that drives dangerous fever, acidosis, hyperkalemia, and muscle breakdown. Because the crisis can progress rapidly, having dantrolene ready allows immediate treatment and dramatically improves outcomes.

Other drugs listed are not targeted cures for malignant hyperthermia. Epinephrine, naloxone, and flumazenil address different emergencies (allergic/anaphylactic reactions, opioid overdose, and benzodiazepine overdose, respectively) and do not stop the MH cascade. They may be used in other intraoperative emergencies, but they won’t treat MH itself.

For susceptible patients, the protocol is to have dantrolene on hand in ample supply and readily accessible in the operating room, with triggers avoided (such as certain anesthetics and muscle relaxants) and supportive measures ready if MH occurs.