A marathon runner collapses in 38 C heat with rectal temperature 41.4 C and altered mental status. Which intervention is the priority?
1Administer acetaminophen 1000 mg orally to lower the core temperature set point
2Begin rapid external cooling with cold water immersion until core temperature reaches 39 C✓ Correct answer
3Apply tepid water sponge baths to gradually lower the core temperature to 39 C
4Administer dantrolene 2.5 mg/kg IV as the specific antidote for exertional heat stroke
Explanation
Exertional heat stroke (CORE temperature over 40 C with neurologic dysfunction) is treated with RAPID COOLING — cold-water (or ice-water) immersion is the gold standard for exertional heat stroke (cools at about 0.15-0.30 C per minute). Goal: core temp under 39 C within 30 minutes. Evaporative cooling (water spray + fans) and ice packs to neck/axilla/groin are alternatives if immersion not feasible. Antipyretics (acetaminophen, aspirin) are INEFFECTIVE because the hypothalamic set point is not elevated. Dantrolene treats malignant hyperthermia — NOT heat stroke (though sometimes used in NMS).