12.1 Exertional Heat Stroke, Hyponatremia & Cold Injury Emergencies

Quick Answer: Exertional heat stroke (EHS) is central-nervous-system (CNS) dysfunction plus a typically rectal temperature ≥40.5°C (105°F). Rectal thermometry is the gold standard. When on-site cold-water immersion (CWI) is available, cool first, transport second: ice water about 35–59°F (1.7–15°C), stir continuously, and stop cooling near 38.9°C (102°F) before the ambulance leaves. Do not use oral, axillary, tympanic, or forehead temperatures to rule out EHS. Exercise-associated hyponatremia (EAH) is overdrinking hypotonic fluid with weight gain—do not give more free water.

Practice Analysis, 8th Edition (PA8) Domain III, task 0303, asks the athletic trainer (AT) to manage emergent conditions, including heat illness, other sudden medical catastrophes, and environmental injury. Chapter 4 covered prevention (wet-bulb globe temperature, acclimatization, staging a tub). This section is treatment. The Korey Stringer Institute (KSI) and the National Athletic Trainers’ Association (NATA) 2015 position statement on exertional heat illnesses (Casa, DeMartini, Bergeron, et al., Journal of Athletic Training 50(9):986–1000) share one operational slogan: cool first, transport second.

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EHS Recognition: Two Criteria, One Thermometer

KSI’s two main diagnostic criteria for EHS are rectal temperature greater than 105°F (40.5°C) immediately post-collapse and CNS dysfunction (irrational behavior, irritability, emotional instability, altered consciousness, collapse, coma, dizziness, confusion, “out of it”). Collapse is not required. Many athletes show CNS change while still standing. Skin is usually hot and wet; classical (classic) heat stroke in the elderly may be dry—do not wait for dry skin in a football player.

Rectal temperature is the only immediate, accurate core measurement in an exercising individual (NATA 2015). Oral, axillary, tympanic, temporal-artery, and forehead-sticker devices are not valid after intense exercise in the heat and can read deceptively “normal.” Exam trap: using an oral or tympanic reading to “rule out” EHS in a collapsed, confused athlete. If rectal thermometry is delayed and the setting plus CNS findings scream EHS, start cooling—do not wait for a gadget. If rectal temperature cannot be measured and CWI is indicated, NATA 2015 advises cool 10–15 minutes, then transport.

If CNS dysfunction is present and the rectal number is slightly under 40.5°C because of delay or passive cooling, still treat as EHS. Survival tracks how long the brain stays above the critical threshold, not how dramatic the first digit looked.

Heat exhaustion is inability to continue exercise in the heat from cardiovascular insufficiency, energy depletion, and central fatigue. Core temperature is usually below 40.5°C (105°F). Sweating is typically heavy. The athlete may have headache, dizziness, or nausea but can often still talk coherently—profound CNS change is absent. Same-day return is not recommended. The moment speech, behavior, or consciousness falls apart, you have left the exhaustion lane.

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Treatment: Cool First, Transport Second

KSI and NATA both treat whole-body CWI as the gold-standard prehospital treatment. Sequence:

1. Remove all equipment and excess clothing.
2. Immerse in a tub or stock tank of ice water approximately 35–59°F (1.7–15°C) (NATA 2015; KSI lists 35–58°F—the same ice-water range). Water this cold is uncomfortable to staff; that is not a reason to add warm water.
3. Stir continuously and add ice so a warm boundary layer does not form around the athlete. NATA 2015 estimated CWI cooling at about 0.37°F/min, or roughly 1°F every three minutes across the immersion period—an approximate clock if rectal monitoring is not possible during treatment.
4. Monitor rectal temperature, heart rate, respiratory rate, blood pressure, and CNS status with the probe left in place when feasible.
5. Activate emergency medical services (EMS) after cooling has been started. Call 911 while the athlete is in the tub; do not wait to “see how they look.”
6. Cease cooling when rectal temperature reaches about 102°F (38.9°C). KSI’s stop window is 101–102°F (38.3–38.9°C) to limit overshoot into iatrogenic hypothermia. The 2020 prehospital EHS consensus (Miller, Casa, et al.) is explicit: stop CWI only when rectal temperature is <38.9°C (102°F).

The goal is to reduce core temperature below 102°F (38.9°C) within 30 minutes of collapse. KSI reports a 100% survival rate when immediate cooling (CWI or aggressive whole-body cold-water dousing) starts within 10 minutes of collapse. Morbidity tracks time above the critical threshold, not how close the hospital is.

If there is no tub, use tarp-assisted cooling with oscillation (TACO): lay a tarp, place the athlete, pour ice and water, lift the edges into a taco, and rock to keep water moving (Luhring et al., JAT 2016; Hosokawa et al., Annals of Emergency Medicine 2017). Published TACO cooling rates are about 0.14–0.17°C/min—far faster than passive rest (~0.04°C/min) and field-viable when a 150-gallon tank will not fit at a trail or cross-country finish. If even TACO is impossible, move to shade and rotate cold, wet towels over as much skin as possible while you build a better cooling method. Towels are a bridge, not a substitute for immersion when a tub exists 20 yards away.

The classic Domain III fail: loading an EHS athlete into an ambulance without cooling because “the emergency department is 10 minutes away.” Ten minutes of uncooled core temperature above 105°F is 10 more minutes of brain cooking. Most ambulances cannot perform whole-body CWI. If a tub is on site, the tub is the treatment; EMS arrives to a cooling patient, then transports after the 102°F target. Write “cool first, transport second” into the venue emergency action plan (EAP) and rehearse it with EMS before August two-a-days. An emergency medical technician who has never seen a sideline tub will otherwise pull the athlete out at 106°F “to go to the hospital.”

Return-to-play after EHS is not a same-week coaching decision. KSI: physician clearance, athlete asymptomatic with normal laboratory studies, no exercise for at least one week, then a supervised, graded return (easy work in a climate-controlled setting before heat, then heat, then equipment).

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Hyponatremia: The Other Encephalopathy

Exercise-associated hyponatremia (EAH) is serum sodium <135 mmol·L⁻¹ during or within 24 hours of physical activity (NATA 2017 fluid-replacement position statement, McDermott et al., JAT 52(9):877–895; 3rd International EAH Consensus, Hew-Butler et al., British Journal of Sports Medicine 2015). The usual mechanism is overdrinking hypotonic fluid—including water and sports drinks—often plus impaired free-water excretion, so body mass is maintained or increases during events lasting about an hour or more. This is not “not drinking enough.”

Field clues: weight gain from pre-event weight, progressive headache, nausea, vomiting, swelling of hands and feet (tight rings, puffy face), confusion, and seizure. Core temperature is often normal or only modestly elevated. The athlete may look “heat sick” because the event was hot and long. Do not give more free water. Do not run a hypotonic intravenous line as a reflex. Mild, stable EAH: withhold fluids until the athlete urinates and is evaluated. Severe EAH with encephalopathy (seizure, coma, suspected cerebral edema) is an EMS / hospital problem; successful treatment uses rapid sodium replacement with hypertonic (3% or greater) saline under advanced protocols—not an athletic-training-room oral-rehydration experiment.

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Four-Way Collapse Contrast: EHS vs EAH vs SCT vs SCA

Without trauma, a collapsed athlete is sudden cardiac arrest (SCA), EHS, exertional collapse associated with sickle cell trait (ECAST / exertional sickling), EAH, or (less often) asthma until the picture clarifies. Treatments conflict, so the first 60 seconds of thinking matter.

SCA is unresponsive collapse with absent or agonal breathing: start compressions and an automated external defibrillator, not a differential lecture. Sickling (NATA/Inter-Association sudden-death best practices): the athlete often slumps to a stop as legs fail, may still converse, and does not show the writhing, rock-hard muscle of classic heat cramps. Known or suspected sickle cell trait plus collapse is a medical emergency—check rectal temperature so you do not miss concurrent EHS, but do not spend the first minutes hunting a tub if the picture is ischemic sickling without hyperthermia.

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Hypothermia: Afterdrop and Gentle Handling

NATA 2008 environmental cold injuries (Cappaert et al., JAT 43(6):640–658) classifies hypothermia as core temperature below 95°F (35°C) in traditional teaching, and uses this field staging: mild core 95–98.6°F (35–37°C) with vigorous shivering and impaired fine motor control; moderate 90–94°F (32–34°C) with depressed vitals, possible cessation of shivering, and impaired mental function; severe below 90°F (32°C) with rigidity, bradycardia, loss of consciousness, and risk of ventricular fibrillation. Rectal temperature with a low-reading probe is preferred; oral, tympanic, and axillary readings fail in the cold. An axillary or oral temperature above 95°F (35°C) means the person is not hypothermic by NATA’s cutoff rule of thumb.

Immediate care: scene safety, primary survey, gentle handling (rough movement of a moderate/severe patient can trigger paroxysmal ventricular fibrillation), remove wet clothing, insulate with dry layers including the head, and move to shelter from wind and rain. Rewarm the trunk first—axilla, chest wall, and groin—not the arms and legs. Peripheral rewarming dilates cold, acidotic extremity blood back into the core (afterdrop), which can drop core temperature further and precipitate arrhythmia. Afterdrop can also appear during rewarming after cold-water immersion; monitor, do not celebrate the first warm blanket and walk away. Provide warm, nonalcoholic fluids and carbohydrate if the patient can swallow safely. Do not apply friction massage if frostbite may be present.

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Frostbite: No Snow Rub, No Freeze–Thaw–Refreeze

Frostbite is freezing of tissue (tissue temperature below 28°F / −2°C). Superficial findings: dry waxy skin, erythema or mottled gray, cold firm areas, transient tingling. Deep findings: hard cold skin, white/gray/black/purple color, vesicles, poor circulation, later hemorrhagic blisters. Never rub snow on frostbite and never massage frozen tissue—ice crystals plus friction tear cells (NATA 2008 rec. 16; CDC winter-weather guidance). Remove wet or tight covering. Do not allow weight-bearing on a frostbitten foot.

Do not thaw if refreeze is likely during transport. NATA 2008: once rewarming has begun, refreeze usually means necrosis. If the bus still has to sit in a −10°F parking lot, protect and evacuate; delay thaw until a setting that can keep the part thawed. When thaw is appropriate and refreeze will not occur, immerse in warm water 98–104°F (37–40°C) (NATA); thawing is painfully complete when tissue is pliable. Direct dry heat (radiator, hair dryer on high) burns numb skin. Cover, splint, and elevate after thaw. Hypothermia takes priority over a frozen finger when both are present.