What vital sign is most likely to indicate the presence of malignant hyperthermia?

Malignant hyperthermia is a severe reaction typically triggered by certain general anesthetics and neuromuscular blockers, leading to a hypermetabolic state in skeletal muscle. One of the key indicators of this condition is an increase in end-tidal carbon dioxide (ETCO2) levels.

During malignant hyperthermia, the body's metabolism accelerates, resulting in increased carbon dioxide production as muscles consume more energy. As the body's ability to eliminate CO2 through ventilation is overwhelmed by the excessive production, the ETCO2 levels rise significantly. This is a critical sign that helps clinicians recognize the onset of malignant hyperthermia, prompting immediate treatment interventions to mitigate the condition.

The other options, while they may be present in various clinical scenarios, do not specifically signify malignant hyperthermia in the same way that increased ETCO2 does. Increased muscle rigidity is a common sign of the condition, but it does not serve as a direct measure of the metabolic changes that are occurring. Therefore, the increase in ETCO2 is directly linked to the hypermetabolic state and is a vital sign healthcare providers monitor closely during anesthesia to identify and manage malignant hyperthermia effectively.