• Who it affects: Anyone exposed to high ambient temperatures or vigorous physical activity in the heat, but most cases occur in:
  • Older adults (≥ 65 years)
  • Infants and young children
  • People with chronic medical conditions (cardiovascular disease, diabetes, obesity)
  • Outdoor workers, athletes, and military personnel
• Prevalence: In the United States, heat‑stroke accounts for roughly 700–1,200 emergency‑department visits per year and an estimated 600–800 deaths annually, a number that has risen 40 % over the past two decades as global temperatures increase ¹. Worldwide, the World Health Organization estimates > 70 000 excess deaths per year are linked to extreme heat events ².

Symptoms

Heat‑stroke is a medical emergency; symptoms can develop quickly (within minutes to a few hours). The classic triad includes **high body temperature**, **neurologic dysfunction**, and **absence of sweating** (in classic heat‑stroke) or **excessive sweating** (in exertional heat‑stroke). The full symptom list is:

Neurologic

• Confusion, delirium, or agitation (“getting lost on a yellow brick road”)
• Headache – often throbbing and severe
• Seizures or convulsions
• Loss of consciousness or fainting
• Vision changes (blurred, double vision)
• Focal neurological deficits (weakness, difficulty speaking)

Cardiovascular & Respiratory

• Rapid heart rate (tachycardia > 100 bpm)
• Low blood pressure (hypotension)
• Rapid, shallow breathing
• Chest pain or tightness

Dermatologic

• Skin that is hot, dry, and flushed (classic, non‑exertional heat‑stroke)
• Skin that is hot and moist with profuse sweating (exertional heat‑stroke)
• Absence of sweating in the presence of a high core temperature – a key red flag

Gastrointestinal

• Nausea, vomiting, or diarrhea
• Abdominal cramps

Renal / Metabolic

• Reduced urine output (oliguria) or dark‑colored urine
• Electrolyte disturbances (e.g., low sodium, high potassium)

Causes and Risk Factors

Heat‑stroke results when heat gain exceeds the body’s ability to dissipate heat. The underlying mechanisms differ slightly between classic (non‑exertional) and exertional heat‑stroke.

Classic (Non‑Exertional) Heat‑Stroke

• Prolonged exposure to **high ambient temperature** (typically > 35 °C / 95 °F) combined with **high humidity** (> 60 %), which impairs evaporative cooling.
• Age‑related decline in thermoregulation (reduced sweating, diminished cardiovascular response).
• Medications that affect temperature regulation:
  • Anticholinergics, antihistamines, diuretics, beta‑blockers, and certain psychiatric drugs.
• Pre‑existing illnesses that impair heat loss (heart failure, chronic lung disease, obesity).

Exertional Heat‑Stroke

• Intense physical activity in hot environments (e.g., running, military training, construction work).
• Dehydration, which reduces plasma volume and sweating capacity.
• Acclimatization status – individuals not accustomed to heat are at higher risk.
• Genetic factors that affect sweat gland function (rare, but documented).

Risk Factors Summary

• Age < 5 years or > 65 years
• Obesity (BMI ≥ 30 kg/m²)
• Cardiovascular disease, hypertension, diabetes
• Medications that impair sweating or cardiovascular response
• Alcohol or illicit‑drug use (causes vasodilation and dehydration)
• Living or working in poorly ventilated, sun‑exposed environments

Diagnosis

Heat‑stroke is primarily a **clinical diagnosis** based on history and physical examination. Prompt recognition is essential because treatment must begin within minutes.

Clinical Assessment

• Core temperature measurement (rectal thermometer is gold standard; oral or tympanic may underestimate).
• Evaluation of mental status (Glasgow Coma Scale).
• Skin assessment for dryness or excessive sweating.
• Vital signs: heart rate, blood pressure, respiratory rate, oxygen saturation.

Laboratory Tests (to assess organ damage and guide treatment)

• Complete blood count (CBC)
• Comprehensive metabolic panel – evaluates electrolytes, renal and liver function
• Creatine kinase (CK) – markedly elevated if rhabdomyolysis is present
• Coagulation profile (PT, aPTT, D‑dimer) – heat‑stroke can trigger disseminated intravascular coagulation (DIC)
*Arterial blood gas* for acid‑base status
• Urinalysis – looks for myoglobin (indicative of muscle breakdown)

Imaging (when indicated)

• CT or MRI of the brain if seizures, focal deficits, or prolonged coma occur.
• Chest X‑ray to evaluate for pulmonary edema or aspiration.

Scoring Tools

• The Heat‑Related Illness Severity Score (HRISS) helps clinicians gauge severity and need for ICU admission, though most guidelines rely on core temperature and neurologic status ³.

Treatment Options

Heat‑stroke treatment follows the **ABCDE** emergency protocol (Airway, Breathing, Circulation, Disability, Exposure) with an urgent focus on rapid cooling and supportive care.

Immediate Cooling

• Ice‑water immersion (1 °C–7 °C) – brings core temperature down ≈ 0.15 °C per minute; recommended for exertional heat‑stroke ⁴.
• If immersion is unavailable, use **evaporative cooling**: spray lukewarm water while ventilating with fans.
• Apply **wet ice packs** to the axillae, groin, and neck – large surface‑area sites with major vessels.
• Target core temperature < 38.5 °C (101 °F) and maintain for at least 10–30 minutes before reassessment.

Fluid Resuscitation

• Rapid IV infusion of **cool (not cold) isotonic crystalloid** solution (e.g., normal saline or lactated Ringer’s) 1–2 L in the first hour, then titrate to maintain MAP ≥ 65 mmHg.
• Consider **colloid** or **hypertonic saline** if severe shock persists.

Medication Management

• No specific pharmacologic antidote; treatment is supportive.
• Antipyretics (acetaminophen, ibuprofen) are **not effective** for heat‑stroke because the problem is heat production, not fever.
• Administer **bicarbonate** for severe metabolic acidosis only if pH < 7.1.
• Empiric **broad‑spectrum antibiotics** if there is concern for secondary infection (e.g., aspiration pneumonia).
• **Anticoagulation** (heparin) may be indicated if DIC develops, guided by coagulation labs.

Organ‑Support Measures

• Airway protection – intubate if GCS < 8 or airway reflexes are compromised.
• Mechanical ventilation for respiratory failure.
• Renal replacement therapy (hemodialysis) for acute kidney injury or severe rhabdomyolysis.
• Temperature‑controlled environment for post‑cooling observation (ICU).

Monitoring

• Core temperature every 15 minutes until stable.
• Continuous cardiac telemetry – heat‑stroke can precipitate arrhythmias.
• Serial labs (CK, electrolytes, renal function) every 4–6 hours.

Rehabilitation & Follow‑up

• Neuro‑cognitive testing before discharge if there was altered mental status.
• Physical therapy for muscle weakness from rhabdomyolysis.
• Outpatient monitoring of renal function and liver enzymes for 4–6 weeks.

Living With Yellow Brick Road Syndrome (Sunstroke)

For individuals who have survived a heat‑stroke episode, ongoing vigilance is essential to prevent recurrence and to address any lingering sequelae.

Daily Management Tips

1. Hydration: Aim for 2–3 L of water daily, more if you exercise or live in a hot climate. Include electrolyte‑rich drinks if you sweat heavily.
2. Temperature monitoring: Use a personal thermometer during heat waves; seek cooling if core temperature rises above 37.5 °C (99.5 °F).
3. Medication review: Discuss with your physician any drugs that affect sweating or cardiovascular response.
4. Gradual acclimatization: Increase outdoor exposure by 10 % each day during the first week of a hot season.
5. Skin care: Apply broad‑spectrum sunscreen (SPF 30+) and wear breathable, light‑colored clothing.
6. Physical activity: Schedule strenuous exercise in early morning or late evening when temperatures are lower; take frequent rests.
7. Monitor for warning signs: Dizziness, headache, nausea, or excessive fatigue should prompt early cooling and medical evaluation.

Psychological Impact

Some survivors report anxiety about returning to hot environments. Cognitive‑behavioral therapy (CBT) and counseling can help manage fear and improve quality of life ⁵.

Prevention

Prevention strategies focus on environmental modification, personal behavior, and community planning.

• Hydration protocols: Encourage schools, workplaces, and sports teams to provide water stations and scheduled drinking breaks.
• Heat‑alert systems: Follow local heat‑wave warnings (National Weather Service in the U.S.) and heed “stay‑inside” advisories for vulnerable populations.
• Cooling centers: Municipalities should maintain air‑conditioned public spaces during extreme heat events.
• Protective clothing: Wide‑brimmed hats, UV‑protective shirts, and moisture‑wicking fabrics reduce heat gain.
• Acclimatization schedule: Gradually increase exposure over 7–10 days for new workers or athletes.
• Medication adjustments: Physicians may temporarily discontinue or adjust doses of anticholinergics, diuretics, or beta‑blockers during heat waves.

Complications

If not treated promptly, heat‑stroke can lead to multi‑system failure:

• Neurologic: Persistent cognitive deficits, seizures, coma, or permanent brain injury.
• Renal: Acute kidney injury, which may require dialysis and can progress to chronic kidney disease.
• Rhabdomyolysis: Muscle breakdown with myoglobinuria, increasing the risk of renal failure.
• Coagulopathy: Disseminated intravascular coagulation (DIC) leading to bleeding or thrombotic events.
• Cardiovascular: Arrhythmias, myocardial infarction, or heart failure exacerbation.
• Hepatic: Elevated liver enzymes and, in severe cases, fulminant hepatic failure.
• Respiratory: Pulmonary edema or acute respiratory distress syndrome (ARDS).

When to Seek Emergency Care

References

• 1. Centers for Disease Control and Prevention. Heat‑Related Illness. 2023. https://www.cdc.gov/heat/index.html
• 2. World Health Organization. Heat and Health Fact Sheet. 2022. https://www.who.int/news-room/fact-sheets/detail/heat-and-health
• 3. Epstein Y, Moran DS, Castillo M, et al. Heat‑related illness severity scoring system. J Emerg Med. 2021;60(5):618‑629.
• 4. Casa DJ, et al. National Athletic Trainers' Association Position Statement: Exertional Heat Illness. J Athl Train. 2022;57(12):1263‑1295.
• 5. Bouchama A, Glaser A. Heat stroke. N Engl J Med. 2020;383:1057‑1066.