Heat stroke — defined as core body temperature >40°C (104°F) with central nervous system dysfunction — is a life-threatening emergency with mortality rates of 10–50% without rapid aggressive cooling. The maxim "cool first, transport second" captures the clinical priority: organ damage from hyperthermia is time-temperature dependent, and delay in cooling is the primary determinant of outcome. Understanding the distinction between heat exhaustion and heat stroke, and the imperative of immediate aggressive cooling, can save lives in clinical and community settings.
The Spectrum of Heat Illness
Heat cramps: muscle spasms from electrolyte depletion in active muscles — benign, treated with oral electrolyte replacement and rest. Heat syncope: transient loss of consciousness from peripheral vasodilation and pooling — usually self-limited with supine positioning. Heat exhaustion: volume depletion and cardiovascular strain from heat stress — elevated temperature (37–40°C), profuse sweating, weakness, nausea, headache, tachycardia, but intact mental status. Treated with rest in cool environment, oral or IV fluid replacement — not immediately life-threatening but requires close monitoring as it can progress to heat stroke. Heat stroke (the emergency): core temperature >40°C + CNS dysfunction (confusion, combativeness, ataxia, seizure, coma). Two subtypes: (1) Classic heat stroke: environmental heat exposure, typically elderly, non-exertional, dry skin (anhidrosis). (2) Exertional heat stroke (EHS): young athletes or military personnel during intense activity — may present with sweating.
Emergency Treatment: Cool First
Target: reduce core temperature to <38.5°C within 30 minutes. Cold water immersion (CWI) — ice water bath at 1–8°C covering trunk and extremities — is the fastest and most effective cooling method, achieving temperature reduction rates of 0.2–0.35°C/min. Superior to ice packs, wet toweling, and evaporative cooling for EHS. Evidence: EHS fatality rates near 0% when CWI is applied within 30 minutes; dramatically higher with delayed cooling. Contraindication: CWI may cause shivering (paradoxical thermogenesis) — ensure continued monitoring. Evaporative cooling (spraying with water + fanning): appropriate when immersion unavailable, particularly for classic heat stroke — reduction rate 0.1–0.15°C/min. Cool IV fluids: provide cardiovascular support and accelerate internal cooling as adjunct — not primary cooling method. Hospital: continuous temperature monitoring (rectal temperature preferred — skin temperature is unreliable), seizure management, rhabdomyolysis monitoring (CK, urine myoglobin), renal function monitoring. For clinical emergency preparedness, our IV vascular access supplies and wound care catalog include essential emergency care equipment, and our PPE section includes cooling garments and monitoring supplies.
