Which of the following is a sign of malignant hyperthermia?

• A. Elevated creatine phosphokinase
• B. Fever
• C. Rigidity
• D. EKG abnormalities

Answer: (A)

Malignant hyperthermia is a rapid, dangerous reaction caused by uncontrolled calcium release in skeletal muscle, which drives a hypermetabolic state and leads to muscle breakdown (rhabdomyolysis). When muscle cells are damaged, their contents, including creatine kinase, spill into the bloodstream, so a marked rise in CK reflects the muscle injury happening during MH. This lab finding is a direct indicator of the underlying process and is commonly used to gauge severity and progression.

Fever is not an early or specific sign of MH; it tends to appear later and can be caused by many other conditions. Rigidity is a notable clinical sign and can occur with MH, but it can occur in other situations as well and isn’t as specific a marker of muscle injury as CK elevation. EKG changes are nonspecific and can result from various electrolyte or cardiac issues, not MH alone.

So, the elevated CK stands out as a clear, lab-confirmed sign of MH-related muscle damage, making it the most fitting choice among the options.