What is the first signal of malignant hyperthermia?

• A. Increased temperature and heart rate.
• B. Decreased blood pressure.
• C. Rash.
• D. Muscle rigidity.

Answer: (A)

Malignant hyperthermia is a life‑threatening hypermetabolic reaction in skeletal muscle triggered by certain anesthetics. The body’s muscle cells release calcium uncontrollably, driving a rapid surge in metabolism, heat production, and CO2 generation. Because the crisis starts with a surge in metabolic activity, the signs you first notice are those reflecting that systemic upsurge. An accelerated heart rate is a very common early sign as the body responds to stress, and a rise in body temperature accompanies the increased heat production from intense muscle activity. Rises in temperature can occur fairly early in many cases, so pairing fever with tachycardia is a plausible early clinical signal that alert clinicians to a developing MH.

Rash is not associated with malignant hyperthermia. Blood pressure can become unstable as the crisis evolves, but a initial drop is not the typical early signal. Muscle rigidity, including jaw (masseter) rigidity, can occur early in MH, especially after certain triggering agents, but it is not the sole or universal first sign and may be overshadowed by the overall metabolic surge reflected by tachycardia and rising temperature.

If MH is suspected, stop the triggering agent, summon help, administer dantrolene, increase ventilation with 100% oxygen, and monitor and correct electrolyte and acid-base disturbances.