What will NOT be a sign of Malignant Hyperthermia?

Malignant Hyperthermia is a serious reaction to certain anesthetic agents, characterized by a set of critical signs and symptoms. Among these, a rapid increase in temperature, increased end-tidal carbon dioxide (ETCO2) levels, and tachycardia are all well-documented indicators of this condition.

The important feature to highlight about decreased muscle tone is that it is not typically associated with Malignant Hyperthermia. In fact, one of the hallmark signs of this condition is increased muscle rigidity, not decreased muscle tone. This rigidity occurs due to uncontrolled calcium release from the sarcoplasmic reticulum of skeletal muscles, leading to the hypermetabolic state characterized by the other symptoms. Therefore, decreased muscle tone is the correct answer to identify what would not be a sign of Malignant Hyperthermia.