What is the first sign of malignant hyperthermia?

• A. Tachycardia
• B. Hypotension
• C. Hypothermia
• D. Seizures

Answer: (A)

In malignant hyperthermia, the trigger causes an abnormal, uncontrolled release of calcium in skeletal muscle, driving a rapid rise in muscle metabolism. The heart responds quickly to this metabolic surge, and tachycardia emerges as the earliest clinical clue. This reflects the sympathetic activation and the body's attempt to cope with the sudden, high metabolic demand and increased CO2 production. Because temperature elevation and other systemic effects develop as the crisis progresses, tachycardia is typically the first sign clinicians notice.

Hypotension tends to appear later as acidosis and vasodilation worsen; hypothermia would be inconsistent with the hypermetabolic heat generation seen in MH; seizures are not the characteristic early sign and usually represent other complications or later stages.