Heat illness: documentation that holds up
Heat stroke is defined by a core temperature and a change in mental status — and it's treated by cooling fast, not by working it up first. The defensible chart shows a rectal core temperature, the time cooling began, the end-organ workup, and that the dangerous mimics were considered.
01What's at stake
Heat stroke (core ≥40°C with CNS dysfunction) is a true emergency with high mortality — but if the core temperature is brought below 40°C within ~30 minutes, mortality approaches zero. There's no confirmatory test, so the failures are relying on an inaccurate oral/tympanic temperature, delaying cooling to finish the workup, and missing a mimic (sepsis, NMS, serotonin syndrome, thyroid storm).
02The spectrum & the can't-miss
- Heat stroke — core ≥40°C plus altered mental status; classic (elderly, heat wave, often dry skin) or exertional (athletes, rapid onset).
- Heat exhaustion — salt/water depletion, core <40°C, no CNS involvement.
- Dangerous mimics — sepsis/meningitis, thyroid storm, NMS, serotonin syndrome, anticholinergic toxidrome, sympathomimetics, salicylate overdose, alcohol withdrawal.
- End-organ damage — rhabdomyolysis/AKI, hepatic injury, DIC, cardiovascular dysfunction.
03History & exam — measure the core
- Rectal (core) temperature — the diagnosis hinges on it; oral, axillary, skin, and tympanic temps are inaccurate and can falsely reassure. → rectal temp
- Mental status change is the cardinal sign separating stroke from exhaustion.
- Risk: age >65, isolation, no A/C, immobility; and thermoregulation-impairing meds (anticholinergics, antihistamines, beta-blockers, diuretics, phenothiazines, TCAs, sympathomimetics).
- Beta-blockers may blunt the expected tachycardia.
Skip the typing
Work the case in the Heat Illness Workup — it records the core temperature, the cooling measures, the glucose/mental-status check, and the end-organ labs, and assembles an MDM that documents the time-critical cooling and the mimics considered.
04Workup & cooling
- Cool first, work up second. Begin cooling immediately, even before the full history/exam.
- Cold/ice-water immersion is the fastest (gold standard for exertional); evaporative mist-and-fan is the better-tolerated alternative for the elderly/classic patient; ice packs to the neck/groin/axillae are adjuncts.
- Stop cooling at ~38.6°C to avoid overshoot hypothermia, and keep monitoring the rectal temperature.
- Antipyretics don't work (and may harm the liver) — hyperthermia isn't a set-point change. Use benzodiazepines for shivering/agitation, not phenothiazines/haloperidol.
- End-organ labs: CK, renal function, LFTs, coagulation, lactate, ECG, CXR, urinalysis; check sodium before large-volume saline in athletes and the elderly (hyponatremia risk).
05What to document
06Where charts fail
- Relying on an oral/tympanic temperature instead of a rectal core temperature.
- Delaying cooling to complete the workup.
- Giving antipyretics for heat stroke, or sedating with phenothiazines/haloperidol.
- Not considering the mimics when temperature won't normalize or agitation persists.
- Discharging the well-appearing young athlete without graded return-to-play, or the elder without a safe-environment check.
07Sources
- Santelli J, Sullivan JM, Czarnik A, Bedolla J. Heat illness in the emergency department: keeping your cool. Emergency Medicine Practice (EB Medicine). 2014;16(8).
- Bouchama A, Knochel JP. Heat stroke. N Engl J Med. 2002;346:1978-1988.
- Casa DJ, McDermott BP, Lee EC, et al. Cold water immersion: the gold standard for exertional heatstroke treatment. Exerc Sport Sci Rev. 2007;35(3):141-149.
- Lipman GS, Eifling KP, Ellis MA, et al. Wilderness Medical Society practice guidelines for heat-related illness. Wilderness Environ Med. 2013;24(4):351-361.
© 2026 Kim Trinh, MD. All rights reserved. Educational only — synthesized from EB Medicine and primary literature. Synthetic examples. Not medical advice — apply local protocol and judgment.