Q: All of the following can be probable first signs of Malignant Hyperthermia (MH) except 

A) Hyperthermia 
B) Hypercarbia 
C) Sinus tachycardia 
D) Masseter muscle rigidity 
E) Generalized muscle rigidity


Answer: A

There is a huge misconception that hyperthermia is the first sign of MH. Actually not!

Atleast one study showed that hyperthermia was the first sign in MH in only about 8 percent of the cases, and the sole initial sign in about four  percent of cases. 

All other choices in question can be the initial presenting signs in MH.


Reference:

Larach MG, Gronert GA, Allen GC, et al. Clinical presentation, treatment, and complications of malignant hyperthermia in North America from 1987 to 2006. Anesth Analg 2010; 110:498.