What symptom would indicate a severe response to malignant hyperthermia?

A severe response to malignant hyperthermia is characterized by a rapid increase in body temperature, often exceeding 38.5°C (101.3°F) and can escalate to much higher levels. This hypermetabolic state is triggered by exposure to certain anesthetic agents or muscle relaxants in susceptible individuals, leading to an uncontrolled release of calcium from the sarcoplasmic reticulum of skeletal muscle cells. As the condition worsens, the metabolic rate increases significantly, resulting in a profound rise in body temperature which is a hallmark of this potentially life-threatening crisis.

While each of the other symptoms mentioned can occur in various medical conditions, the drastic and unchecked rise in body temperature is the most indicative of severe malignant hyperthermia. Recognizing this key symptom allows for prompt intervention, which is critical in managing the condition and preventing serious complications such as cardiopulmonary failure or death. Thus, the increase in body temperature stands out as the most significant symptom of a severe reaction.