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Exertional Heat Stroke
From WikiSM
Contents
Other Names
- Heat stroke
- Exertional Heat Stroke (EHS)
Background
- This page refers to heat stroke, a condition characterized by extreme hyperthermia and CNS dysfunction[1]
- This page primarily focuses on Exertional Heat Stroke (EHS) seen in athletes
- The overlap with 'classic' heat stroke is significant
History
Epidemiology
- Mortality
- Trending
Pathophysiology

Epidemiologic and Clinical Features of Classic and Exertional Heatstroke..jpeg[6]
- General
- Severe end of heat related illness spectrum characterized by severe hyperthermia, neurologic dysfunction
- This is a life threatening condition and medical emergency
- Universally fatal if left untreated
- The most critical interventions are to remove the patient from the heated environment to cool conditions
- Subsequently, submersion in ice water to cool the patient
- Timeline
- In American football, most cases occur during summer practice where players are less fit, temperature and humidity are high
Terminology
- Heat stroke
- Defined as "core temperature above 40°C (104°F) PLUS central nervous system involvement
- Exertional Heat Stroke
- Exertional heat stroke has the added component of a pathologic hyperthermia that occurs during strenuous activity
- Triad: hyperthermia, neurologic dysfunction, recent physical exertion
- Classic (Passive)
- Seen in elderly and children
- Due to exposure to environmental heat and poor heat-dissipation mechanisms
- Typically occurs as an epidemic during a heat wave in those who can not care for themselves
- Exertional
- Associated with physical exercise
- Results when excessive production of metabolic heat overwhelms physiological heat-loss mechanisms
- Most often affects healthy young persons who receive prompt recognition, treatment
- Can occur in first 60 minutes of exertion
- Can be triggered without exposure to high ambient temperatures[7]
Environmental Evaluation
- WBGT should be used to assess risk.
Etiology

Pathophysiological Pathway Leading to Heat Stroke[6]
- General
- Occurs when the body's metabolic heat production exceeds its ability for heat transfer
- Subsequently results in thermoregulatory dysfunction, metabolic disruption
- Metabolic dysfunction
- Interleukins's, cytokines, and heat shock proteins are released or disrupted resulting in pathophysiology similar to shock mechanisms.
- For example, heat shock proteins become denatured, are no longer able to protect other proteins or enzymes from thermal destruction
- Apoptosis and necrosis begin to occur at this level and begin to cause organ dysfunction.
- Multiorgan dysfunction[8]
- More pronounced in EHS than classic heat stroke
- Peaks around 24 to 48 hours
- Primarily to heat-induced necrotic and apoptotic cell death
- Accompanying widespread microthrombosis, hemorrhage, and inflammatory injury
Associated Conditions
Three Phases
- Hyperthermic–neurologic acute phase
- Most critical to recognize
- Hematologic–enzymatic phase
- Peaking 24 to 48 hours after the event
- Late renal–hepatic phase
- If clinical symptoms are sustained for 96 hours or longer

Risk Factors Underlying Heat stroke (click to enlarge)[6]
Risk Factors
Differential Diagnosis
Differential Diagnosis Heat Illness
- Minor
- Major
Differential Diagnosis Collapsed Athlete
- Cardiac Arrest
- Exertional Heat Stroke
- Sports Related Concussion
- Exercise Associated Hyponatremia
- Hypoglycemia
- Hypothermia
- Exercise Associated Collapse
Clinical Features

Signs and symptoms of exertional heat stroke[9]
- History
- In EHS, typically some sort of explanation for elevated core temperature
- E.g. exercising outdoors, no access to air conditioning, landscaping
- In most cases the athlete or laborer will collapse, prompting attention
- In EHS, typically some sort of explanation for elevated core temperature
- Physical Exam
- Hyperthermia with core temp greater 40°C (104°F)
- CNS dysfunction (altered behavior, confusion, slurred speech, delirium, ataxia, coma, seizures)
- Seizures and sphincter incontinence are more common in EHS (need citation)
- Anhidrosis frequently present (absence does not exclude heat stroke)
- Hematochezia (can occur from decreased intestinal perfusion, ischemia)
- Special Tests
Evaluation
- Primarily a clinical diagnosis
- Based on triad of exposure or exertion, hyperthermia, CNS dysfunction
- Workup (imaging, labs, EKG, etc) should not delay primary treatment of cooling
Radiographs
- Standard Radiograph Chest
- Chest xray should be obtained
CT
- Should be obtained to exclude other causes
Labs
- Blood glucose finger stick
- Complete Blood Count
- Metabolic Panel
- Liver Function Tests
- Blood Gas
- Lactate
- Coagulation studies
- Creatinine phosphokinase, myoglobin
- Risk of Rhabdomyolysis is high
- Urinalysis
Classification
- There is no widely accepted classification system

Field management of suspected heat stroke[9]
Management
Prehospital
- Rapid Recognition
- Typically triggered by collapse or near collapse of the athlete
- Prehospital management is the most critical element to limiting morbidity and mortality[10]
- Attempt to distinguish EHS from other forms of heat related illness
- All patients suspected of having EHS should be transported to the hospital
- ABCs/ Rapid Assessment
- Confirm presence of pulse, spontaneous respirations
- Patient may require airway management prehospital
- Maintain oxygen saturation >90%
- Patient should be given IVF bolus, especially if hypotensive
- Rapid Cooling
- The best outcomes for EHS involve rapid on-site whole-body cooling (need citation)
- Cooling should be initiated as soon as EHS is suspected
- Monitor temperature if possible
- Remove from warm environment into air conditioned environment

Onsite whole-body cooling strategies for EHS casualties that are effective in the field.[9]
- Cooling Techniques
- Ice water tub immersion if possible[11]
- Rotate ice-water soaked towels on trunk, extremities, head
- Place ice packs in axilla, groin, behind knees
- Douse body with ice water
- Spray with tap water
- EMS/ Tansport
- Transport as soon as possible
- Timing may depend somewhat on field resources, comfort of on-site team
- EMS should actively cool en route to hospital
Hospital
- ABC
- Patient may require intubation
- Fluids
- Bolus if hypotensive
- Protects kidneys from highly likely rhabdomyolysis
- Fluids should be cold
- Complications
- Hypotensive shock requiring pressors
- Electrolyte dysfunction: hypo- or hyperkalemia, hyponatremia
- Liver injury
- Renal Failure
- ARDS
- Seizure: treat with benzodiazepines
Cooling
- General
- Critical threshold is 40.5°C, above which mortality skyrockets
- Cooling end point is 38-39°C (do not want to over-correct)
- Cooling faster than 0.10°C is safe and desirable for improving prognosis[12]
- Foley catheter for core temperature monitoring
- No role for dantrolene, antipyretics
- Cold Water Immersion
- Treatment of choice
- Immerse body to the level of torso or neck in ice water
- Benefits: quickest decrease in core temperature, some studies have shown 100% survival when started early
- Can cool as fast as 0.20°C to 0.35°C per minute
- Disadvantages: immersion tub not available in most EDs, not well tolerated, hard to resuscitate
- Ice packs to neck, axilla, groin, popliteal fossa similar benefit?
- Evaporative/ Convective Cooling
- Spray cold water on patient with fans directed at them
- Can spray on skin or thin sheet
- Benefits: Easier and quicker to apply in ED while performing other interventions
- Disadvantage: slower than immersion, slightly higher morbidity and mortality
- May be only option in austere environments where ice or transportation is not readily available
- Invasive techniques with limited ata
- Bladder lavage
- Gastric lavagage
- Tube thoracostomy with lavage
- ECMO or cardiopulmonary bypass
Prevention
Rehab and Return to Play
Rehabilitation
- There are no clear rehabilitation guidelines
Return to Play/ Work

Example of staged return to play after exertional heat stroke (click to enlarge)[9]
- No comprehensive guidelines
- RTP or work decisions are challenging for physicians
- At a minimum, clinical and laboratory findings need to return to baseline
- Most athletes recover within a few weeks, especially if recognized and treated early[13]
- American College of Sports Medicine[9]
- Decision may involve medical staff, coaches, supervisors, athletic trainers, and/or family members
- Athlete should go through a progressive increase in exercise intensity and duration in warm or hot conditions to assess recovery
- If athlete can gradually regain preheat injury exercise tolerance and expected performance
- Return to play is usually safe and advancing to full training and competition is acceptable
- Heat Tolerance Testing (HTT)
- May be required for athletes who are unable to advance activities in a reasonable time frame
- Used by Israel Defense Force (IDF) Medical Corps 6 wk postexertional heat illness as part of the “return to duty” criteria[14]
- Sensitivity (66.7%), specificity (77.7%), and diagnostic accuracy (77.2%) of the HTT[15]
- Authors: risk of EHI recurrence is measurable and that a negative HTT result is associated with a substantial reduction of EHI risk
- Note that this HTT has not been externally validated and requires more research
Complications and Prognosis
Prognosis
- Rate of improvement/ recovery
- If treatment is prompt, milder cases abate within a few days and most patients recover completely
- Prognosis worsens if kidney and liver dysfunction are sustained for more than 96 hours
- Risk of Death
Complications
- Persistent Neurological Deficit
- Seen in 20% of of patients
- Commonly affects cerebellum
- Injury to autonomic nervous system
- Injury to enteric nervous system
See Also
References
- ↑ Bouchama, Abderrezak, and James P. Knochel. "Heat stroke." New England journal of medicine 346.25 (2002): 1978-1988.
- ↑ Bouchama, Abderrezak, and James P. Knochel. "Heat stroke." New England journal of medicine 346.25 (2002): 1978-1988.
- ↑ Shapiro, Y., and D. S. Seidman. "Field and clinical observations of exertional heat stroke patients." Medicine and science in sports and exercise 22.1 (1990): 6-14.
- ↑ Armed Forces Health Surveillance Center (AFHSC. "Update: heat injuries, active component, US Armed Forces, 2013." Msmr 21.3 (2014): 10-13.
- ↑ Mueller, F., and R. Cantu. "Catastrophic sports injury research: twenty-sixth annual reports." University of North Carolina (2008).
- ↑ 6.0 6.1 6.2 Epstein, Yoram, and Ran Yanovich. "Heatstroke." New England Journal of Medicine 380.25 (2019): 2449-2459.
- ↑ Epstein, Y. O. R. A. M., et al. "Exertional heat stroke: a case series." Medicine and science in sports and exercise 31.2 (1999): 224-228.
- ↑ Roberts, George T., et al. "Microvascular injury, thrombosis, inflammation, and apoptosis in the pathogenesis of heatstroke: a study in baboon model." Arteriosclerosis, thrombosis, and vascular biology 28.6 (2008): 1130-1136.
- ↑ 9.0 9.1 9.2 9.3 9.4 Roberts, William O., et al. "ACSM expert consensus statement on exertional heat illness: recognition, management, and return to activity." Current sports medicine reports 20.9 (2021): 470-484.
- ↑ Belval LN, Casa DJ, Adams WM, et al. Consensus statement — prehospital care of exertional heat stroke. Prehosp. Emerg. Care. 2018; 22:392–7.
- ↑ Armstrong LE, Crago AE, Adams R, et al. Whole-body cooling of hyperthermic runners: comparison of two field therapies. Am. J. Emerg. Med. 1996; 14:355–8.
- ↑ McDermott, Brendon P., et al. "Acute whole-body cooling for exercise-induced hyperthermia: a systematic review." Journal of athletic training 44.1 (2009): 84-93.
- ↑ Laitano O, Leon LR, Roberts WO, Sawka MN. Controversies in exertional heat stroke diagnosis, prevention, and treatment. J. Appl. Physiol. 2019; 127:1338–48.
- ↑ Epstein Y. Heat intolerance: predisposing factor or residual injury? Med. Sci. Sports Exerc. 1990; 22:29–35.
- ↑ Schermann H, Craig E, Yanovich E, et al. Probability of heat intolerance: standardized interpretation of heat-tolerance testing results versus specialist judgment. J. Athl. Train. 2018; 53:423–30.
- ↑ Gaudio FG, Grissom CK. Cooling Methods in Heat Stroke. J Emerg Med. 2015 Oct 31.
- ↑ Wallace, Robert F., et al. "Prior heat illness hospitalization and risk of early death." Environmental research 104.2 (2007): 290-295.
Created by:
John Kiel on 30 June 2019 22:50:33
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Last edited:
19 August 2022 07:03:49
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