Which of the following is NOT a sign of elevated sympathetic activity after TBI?

• A. Increased heart rate
• B. Increased respiratory rate
• C. Hypothermia
• D. Diaphoresis

Answer: (C)

Elevated sympathetic activity drives a rapid, whole-body arousal characteristic of a fight-or-flight response. That supercharging of the autonomic nervous system typically shows up as a faster heart rate, quicker breathing, and sweating. Diaphoresis is a hallmark of this surge because sweat glands are activated by sympathetic nerves. Hypothermia, by contrast, reflects cooling of the body or impaired heat production rather than an active sympathetic surge; it indicates a different dysregulation or environmental factors, not the typical elevated sympathetic drive after brain injury. So the sign that does not fit the pattern is hypothermia.