Heat stroke differs from heat exhaustion in that heat stroke involves which of the following?

• A. Core temperature > 40°C with CNS dysfunction
• B. Low core temperature
• C. Diaphoresis without CNS symptoms
• D. Fever without dehydration

Answer: (A)

Heat stroke is defined by extreme hyperthermia with central nervous system dysfunction. When core temperature rises above about 40°C, the body's cooling mechanisms fail and the brain becomes impaired, leading to confusion, agitation, seizures, or loss of consciousness. This brain involvement is what sets heat stroke apart from heat exhaustion, where individuals are typically dehydrated and fatigued but maintain normal or only mildly elevated mental status. The other options don’t fit: a low core temperature would indicate hypothermia, not heat illness; sweating with no CNS symptoms is more characteristic of heat exhaustion; and fever suggests an infection with a regulated set-point, not the nonfever hyperthermia seen in heat stroke.