Heat stroke: Difference between revisions

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==Background==
==Background==
*Severe end of heat-related illness spectrum
*Severe, life-threatening end of the [[heat emergencies|heat illness]] spectrum
*True emergency - universally fatal if left untreated
*Defined as core temperature >40°C (104°F) with CNS dysfunction
**Mortality approaches 30% even with treatment<ref name="Gaudio">Gaudio FG, Grissom CK. Cooling Methods in Heat Stroke. J Emerg Med. 2015 Oct 31.</ref>
*'''Universally fatal if untreated'''; mortality approaches '''30% even with treatment'''<ref>Gaudio FG, Grissom CK. Cooling Methods in Heat Stroke. ''J Emerg Med''. 2016;50(4):563-72. PMID 26525947</ref>
*Hallmark is multisystem organ dysfunction from heat-induced damage resulting in systemic inflammatory response
*Mortality directly correlates with duration and degree of elevated core temperature
*Hallmark is multisystem organ dysfunction from heat-induced systemic inflammatory response


===Types===
===Types===
*Classic (nonexertional) - insidious development over days
*Classic (nonexertional):
**Seen in children and elderly
**Insidious development over days
**During the time of [[heat wave]]
**Seen in elderly, children, chronically ill, those on anticholinergic or diuretic medications
*Exertional - rapid onset during exercise or other exertion
**During heat waves
**Seen in otherwise young, healthy individuals
*Exertional:
**Rapid onset during exercise or physical exertion
**Seen in otherwise young, healthy individuals (athletes, military, laborers)
**Typically faster presentation and higher CK levels


==Clinical Features==
==Clinical Features==
*Symptoms<ref name="Becker">Becker JA, Stewart LK. Heat-related illness. Am Fam Physician. 2011 Jun 1;83(11):1325-30.</ref>
*Core temperature >40°C (104°F) PLUS
**Elevated temperature >40°C (104°F) '''PLUS'''
*CNS dysfunction<ref>Becker JA, Stewart LK. Heat-related illness. ''Am Fam Physician''. 2011;83(11):1325-30. PMID 21661715</ref>:
**CNS neurologic abnormalities (e.g. inappropriate behavior, [[Confusion]], [[dysarthria|slurred speech]], [[Delirium]], [[Ataxia]], [[Coma]], [[Seizures]])
**Altered mental status, confusion, agitation, slurred speech
*Anhidrosis is frequently present; however, its absence does NOT rule out heat stroke
**Ataxia, [[seizures]], coma
*May have massive [[rectal bleeding|hematochezia]] secondary to decreased intestinal perfusion and ischemia<ref>Lambert GP. Intestinal barrier dysfunction, endotoxemia, and gastrointestinal  symptoms: the 'canary in the coal mine' during exercise-heat stress? Med Sport Sci. 2008;53:61-73.</ref>
**Inappropriate behavior may be earliest sign
*Anhidrosis is frequently present but its absence does NOT rule out heat stroke
**Sweating may still be present, especially in exertional heat stroke
*Tachycardia, [[hypotension]] (high-output state → eventual cardiovascular collapse)
*Tachypnea
*Massive hematochezia may occur from intestinal ischemia<ref>Lambert GP. Intestinal barrier dysfunction during exercise-heat stress. ''Med Sport Sci''. 2008;53:61-73. PMID 19208999</ref>
*Petechiae, purpura (DIC)


==Differential Diagnosis==
==Differential Diagnosis==
{{Template:Heat Emergencies}}
{{Altered mental status and fever DDX}}
{{Environmental heat illness DDX}}


===Non-Environmental===
*Key diagnoses to consider:
*Infectious
**[[Sepsis]] / [[meningitis]] / [[encephalitis]]
**[[Sepsis (Main)|Sepsis]]
**[[Meningitis]]
**[[Encephalitis]]
**[[Malaria]]
**[[Typhoid]]
**[[Tetanus]]
*Endocrine
**[[Thyroid storm]]
**[[Thyroid storm]]
**[[Pheochromocytoma]]
**[[Neuroleptic malignant syndrome]]
**[[Diabetic ketoacidosis|DKA]]
*Neurologic
**Hypothalamic [[ICH|bleeding]] or [[stroke|infarct]]
**[[Stroke (main)|CVA]]
**[[Status epilepticus]]
*Toxicologic
**[[Anticholinergic toxicity|Anticholinergic toxidrome]]
**[[Sympathomimetic toxicity]]
**[[Salicylate toxicity]]
**[[Serotonin syndrome]]
**[[Serotonin syndrome]]
**[[Malignant hyperthermia]]
**[[Malignant hyperthermia]]
**[[Neuroleptic malignant syndrome]]
**[[Anticholinergic toxicity]]
**Withdrawal (e.g. [[ETOH withdrawal|ETOH]], [[benzodiazepine withdrawal|benzodiazepines]])
**Sympathomimetic toxicity ([[cocaine]], [[amphetamines]])
**[[Alcohol withdrawal]] / [[benzodiazepine withdrawal]]
 
==Evaluation==
*Core temperature (rectal or bladder probe preferred; tympanic/temporal unreliable)
**Continuous monitoring essential (bladder temperature probe ideal)
*'''Blood glucose''' (POC immediately)
*ECG: most often sinus tachycardia; ischemic changes (ST depressions, TWI) may occur<ref>Mimish L. Electrocardiographic findings in heat stroke and exhaustion. ''J Saudi Heart Assoc''. 2012;24(1):35-39. PMID 23960068</ref>
*CBC: may show hemoconcentration initially; thrombocytopenia with DIC
*BMP: electrolyte abnormalities (variable hypo/hypernatremia, hypokalemia), [[AKI]]
*LFTs: transaminase elevation occurs in nearly all cases (peaks at 48-72h)
**AST/ALT >1000 suggests severe liver injury
*Coagulation studies: PT/INR, fibrinogen, D-dimer (DIC screening)
*CK and myoglobin: [[rhabdomyolysis]] (exertional >> classic)
*Lactate: marker of tissue hypoperfusion
*VBG/ABG: metabolic acidosis
*Urinalysis: myoglobinuria
*CT head ± LP: if concern for CNS infection or hemorrhage
 
==Management==
===Immediate===
*Cooling is THE priority — every minute of delay increases mortality
*Remove from hot environment; remove clothing
*Address ABCs; intubate if necessary for airway protection
*Goal: reduce core temperature to 39°C (102.2°F) within 30 minutes
*Cooling rate target: 0.15-0.25°C/min


{{AMS and fever DDX}}
===Rapid Cooling Techniques===
====Cold Water Immersion (Treatment of Choice)====
*Most effective cooling method (cooling rate ~0.2°C/min)<ref>Pryor RR, et al. Exertional heat illness: emerging concepts and advances in prehospital care. ''Prehosp Disaster Med''. 2015;30(3):297-305. PMID 25959925</ref>
*Immerse body to torso or neck in cold/ice water (1-17°C)
*Best for exertional heat stroke in young/healthy patients
*Also beneficial in elderly patients
*Studies show up to 100% survival when initiated within 30 minutes of collapse<ref>Becker JA, Stewart LK. Heat-related illness. ''Am Fam Physician''. 2011;83(11):1325-30. PMID 21661715</ref>
*Disadvantage: limited access to resuscitative measures during immersion


==Evaluation==
====Evaporative/Convective Cooling====
===Workup===
*Spray lukewarm water (15°C / 59°F) continuously on patient while directing fans at exposed skin
*[[ECG]]<ref>Mimish L. Electrocardiographic findings in heat stroke and exhaustion: A study on Makkah pilgrims. J Saudi Heart Assoc. 2012 Jan; 24(1): 35–39.</ref>
*Easier to apply while performing other interventions in ED
**Most often sinus tachycardia, self-limited
*Slower cooling rate than immersion
**Less frequently ischemic changes including ST depressions, TWIs
*Core temperature (continuous monitoring is ideal, e.g. with bladder temperature monitor)
*Blood glucose
*CBC
*Metabolic panel
*[[LFTs]]
*Blood gas
*[[Lactate]]
*Coagulation studies ([[DIC (Disseminated Intravascular Coagulation)|DIC]])
*Creatine phosphokinase and myoglobin ([[Rhabdomyolysis]])
*[[Urinalysis]]
*[[CXR]]
*[[CT brain]] (± [[LP]]), if indicated (Cerebral Edema)


===Evaluation===
====Other Techniques====
*Clinical diagnosis
*Cold IV fluids (4°C NS bolus) as adjunct (limited cooling on its own)
*Exposure to hot environment and high index of suspicion.
*Ice packs to entire body surface (better than just neck/axillae/groin)
**Ice packs only to neck, axillae, groin provides minimal cooling
*Invasive lavage (bladder, gastric, thoracic) — limited data, reserved for refractory cases
*ECMO — for refractory heat stroke


==Management==
===What NOT to Do===
*Address ABCs
*NO antipyretics (acetaminophen, NSAIDs) — thermoregulatory set point is normal; these are ineffective and may worsen liver/renal injury
*Rapid cooling (see below) - mainstay of treatment
*NO dantrolene — not effective in heat stroke (heat stroke is not malignant hyperthermia)
**Reduces morbidity/mortality, should be started in prehospital setting if no other life-threats exist<ref name="Becker" />
*AVOID peripheral vasoconstrictors (norepinephrine) — may redirect blood from skin and impair cooling
*Remove from environment
*AVOID shivering (counterproductive) — treat with benzodiazepines if occurs during cooling
*[[IVF]] (for renal protection and avoiding rhabdomyolysis)
**Bolus if hypotensive
**Infusion titrated to UOP (goal 2-3ml/kg/hr)


===Rapid Cooling===
===Supportive Care===
*Cooling end point should be ~39°C (102.2°F) - no good data for this goal<ref name="Gaudio" />
*IV fluid resuscitation:
*No role for: antipyretics or dantrolene
**Bolus 500-1000 mL NS if hypotensive
*Combination of methods, or adjuncts such as cool IVF may increase efficacy of individual methods
**Titrate to UOP goal 1-2 mL/kg/hr (renal protection from rhabdomyolysis)
====Techniques====
*Seizures: [[benzodiazepines]] (lorazepam 2-4 mg IV)
*Cool water immersion - treatment of choice<ref name="Becker" /><ref name="Pryor" />
*Hypotension: small fluid boluses first; if refractory, consider dopamine or dobutamine
**Immersion of body to level of torso or neck in cool or ice-water
*Correct electrolyte abnormalities
**Best for exertional heat stroke in young/healthy patients, but benefit shown in elderly patients as well
*Treat [[DIC]] with blood products if clinically significant bleeding
**Diffuse application of ice or cold packs to entire body may provide similar benefit (but less data)
***Applying ice packs only to neck, axillae, groin provides only minimal cooling<ref name="Gaudio" />
**Benefits: most rapid decrease in temperature, some studies have shown 100% survival (esp when started within 30 minutes of collapse)<ref name="Gaudio" /><ref name="Becker" /><ref name="Pryor">Pryor RR, Roth RN, Suyama J, Hostler D. Exertional heat illness: emerging concepts and advances in prehospital care. Prehosp Disaster Med. 2015 Jun;30(3):297-305.</ref>
**Disadvantages: requires special equipment (may not be immediately available), poorly tolerated, unable to provide defibrillation or many other resuscitative measures
*Evaporative/Convective Cooling
**Spray cool water (15°C / 59°F) on patient while directing fans at patient
**Benefits: Easier to apply in ED and while performing other interventions
**Disadvantages: Slower cooling (than immersion) with slightly higher morbidity/mortality
*Invasive
**Techniques such as cardiopulmonary bypass/ECMO or cold water lavage of body cavities has been reported, but inadequate data to recommend<ref name="Gaudio" />


==Complications==
==Complications==
*[[Hypotension]]
*Hepatic injury: almost always present; usually reversible but can progress to fulminant failure
**Usually responds to small fluid bolus (500cc) and body cooling
*[[Rhabdomyolysis]] → [[acute kidney injury]] (more common in exertional)
**If no response to fluids → consider [[vasopressors]] (dopamine or dobutamine)
*[[DIC]] and abnormal bleeding
***Avoid peripheral vasoconstriction (e.g. norepinephrine), which may redirect blood flow away from skin and diminish cooling
*[[Electrolyte abnormalities]]
**Variable: [[hypokalemia]] and [[hypernatremia|hyper]] or [[hyponatremia]] may be seen
*Hematologic - [[DIC]] or abnormal bleeding
*[[hepatic failure|Hepatic injury]] - almost always reversible
*[[Renal failure]]
*[[ARDS]]
*[[ARDS]]
*[[Seizure]] - treat with [[Benzodiazepines]]
*Persistent neurologic deficits: present in ~20% of survivors, associated with high mortality
*[[focal neuro deficits|Neurologic deficit]]
*Seizures
**Persistent in 20%, associated with high mortality
*Myocardial injury


==Disposition==
==Disposition==
*All patients require admission
*All patients require admission (most to ICU)
*Serial monitoring of core temperature, LFTs, coagulation studies, renal function, CK for 48-72h
*LFTs may worsen for 2-3 days after presentation — repeat at 24-48h


==See Also==
==See Also==
*[[Heat emergencies]]
*[[Heat emergencies]]
*[[Heat exhaustion]]
*[[Heat exhaustion]]
*[[Acute fever]]
*[[Rhabdomyolysis]]
*[[Malignant hyperthermia]]
*[[Neuroleptic malignant syndrome]]


==References==
==References==
<references/>
<references/>
*Hifumi T, et al. Heat stroke. ''J Intensive Care''. 2018;6:30. PMID 29850022
*Leon LR, Bouchama A. Heat stroke. ''Compr Physiol''. 2015;5(2):611-647. PMID 25880507


[[Category:Environmental]]
[[Category:Environmental]]

Latest revision as of 09:36, 22 March 2026

Background

  • Severe, life-threatening end of the heat illness spectrum
  • Defined as core temperature >40°C (104°F) with CNS dysfunction
  • Universally fatal if untreated; mortality approaches 30% even with treatment[1]
  • Mortality directly correlates with duration and degree of elevated core temperature
  • Hallmark is multisystem organ dysfunction from heat-induced systemic inflammatory response

Types

  • Classic (nonexertional):
    • Insidious development over days
    • Seen in elderly, children, chronically ill, those on anticholinergic or diuretic medications
    • During heat waves
  • Exertional:
    • Rapid onset during exercise or physical exertion
    • Seen in otherwise young, healthy individuals (athletes, military, laborers)
    • Typically faster presentation and higher CK levels

Clinical Features

  • Core temperature >40°C (104°F) PLUS
  • CNS dysfunction[2]:
    • Altered mental status, confusion, agitation, slurred speech
    • Ataxia, seizures, coma
    • Inappropriate behavior may be earliest sign
  • Anhidrosis is frequently present but its absence does NOT rule out heat stroke
    • Sweating may still be present, especially in exertional heat stroke
  • Tachycardia, hypotension (high-output state → eventual cardiovascular collapse)
  • Tachypnea
  • Massive hematochezia may occur from intestinal ischemia[3]
  • Petechiae, purpura (DIC)

Differential Diagnosis

Template:Altered mental status and fever DDX Template:Environmental heat illness DDX

Evaluation

  • Core temperature (rectal or bladder probe preferred; tympanic/temporal unreliable)
    • Continuous monitoring essential (bladder temperature probe ideal)
  • Blood glucose (POC immediately)
  • ECG: most often sinus tachycardia; ischemic changes (ST depressions, TWI) may occur[4]
  • CBC: may show hemoconcentration initially; thrombocytopenia with DIC
  • BMP: electrolyte abnormalities (variable hypo/hypernatremia, hypokalemia), AKI
  • LFTs: transaminase elevation occurs in nearly all cases (peaks at 48-72h)
    • AST/ALT >1000 suggests severe liver injury
  • Coagulation studies: PT/INR, fibrinogen, D-dimer (DIC screening)
  • CK and myoglobin: rhabdomyolysis (exertional >> classic)
  • Lactate: marker of tissue hypoperfusion
  • VBG/ABG: metabolic acidosis
  • Urinalysis: myoglobinuria
  • CT head ± LP: if concern for CNS infection or hemorrhage

Management

Immediate

  • Cooling is THE priority — every minute of delay increases mortality
  • Remove from hot environment; remove clothing
  • Address ABCs; intubate if necessary for airway protection
  • Goal: reduce core temperature to 39°C (102.2°F) within 30 minutes
  • Cooling rate target: 0.15-0.25°C/min

Rapid Cooling Techniques

Cold Water Immersion (Treatment of Choice)

  • Most effective cooling method (cooling rate ~0.2°C/min)[5]
  • Immerse body to torso or neck in cold/ice water (1-17°C)
  • Best for exertional heat stroke in young/healthy patients
  • Also beneficial in elderly patients
  • Studies show up to 100% survival when initiated within 30 minutes of collapse[6]
  • Disadvantage: limited access to resuscitative measures during immersion

Evaporative/Convective Cooling

  • Spray lukewarm water (15°C / 59°F) continuously on patient while directing fans at exposed skin
  • Easier to apply while performing other interventions in ED
  • Slower cooling rate than immersion

Other Techniques

  • Cold IV fluids (4°C NS bolus) as adjunct (limited cooling on its own)
  • Ice packs to entire body surface (better than just neck/axillae/groin)
    • Ice packs only to neck, axillae, groin provides minimal cooling
  • Invasive lavage (bladder, gastric, thoracic) — limited data, reserved for refractory cases
  • ECMO — for refractory heat stroke

What NOT to Do

  • NO antipyretics (acetaminophen, NSAIDs) — thermoregulatory set point is normal; these are ineffective and may worsen liver/renal injury
  • NO dantrolene — not effective in heat stroke (heat stroke is not malignant hyperthermia)
  • AVOID peripheral vasoconstrictors (norepinephrine) — may redirect blood from skin and impair cooling
  • AVOID shivering (counterproductive) — treat with benzodiazepines if occurs during cooling

Supportive Care

  • IV fluid resuscitation:
    • Bolus 500-1000 mL NS if hypotensive
    • Titrate to UOP goal 1-2 mL/kg/hr (renal protection from rhabdomyolysis)
  • Seizures: benzodiazepines (lorazepam 2-4 mg IV)
  • Hypotension: small fluid boluses first; if refractory, consider dopamine or dobutamine
  • Correct electrolyte abnormalities
  • Treat DIC with blood products if clinically significant bleeding

Complications

  • Hepatic injury: almost always present; usually reversible but can progress to fulminant failure
  • Rhabdomyolysis → acute kidney injury (more common in exertional)
  • DIC and abnormal bleeding
  • ARDS
  • Persistent neurologic deficits: present in ~20% of survivors, associated with high mortality
  • Seizures
  • Myocardial injury

Disposition

  • All patients require admission (most to ICU)
  • Serial monitoring of core temperature, LFTs, coagulation studies, renal function, CK for 48-72h
  • LFTs may worsen for 2-3 days after presentation — repeat at 24-48h

See Also

References

  1. ↑ Gaudio FG, Grissom CK. Cooling Methods in Heat Stroke. J Emerg Med. 2016;50(4):563-72. PMID 26525947
  2. ↑ Becker JA, Stewart LK. Heat-related illness. Am Fam Physician. 2011;83(11):1325-30. PMID 21661715
  3. ↑ Lambert GP. Intestinal barrier dysfunction during exercise-heat stress. Med Sport Sci. 2008;53:61-73. PMID 19208999
  4. ↑ Mimish L. Electrocardiographic findings in heat stroke and exhaustion. J Saudi Heart Assoc. 2012;24(1):35-39. PMID 23960068
  5. ↑ Pryor RR, et al. Exertional heat illness: emerging concepts and advances in prehospital care. Prehosp Disaster Med. 2015;30(3):297-305. PMID 25959925
  6. ↑ Becker JA, Stewart LK. Heat-related illness. Am Fam Physician. 2011;83(11):1325-30. PMID 21661715
  • Hifumi T, et al. Heat stroke. J Intensive Care. 2018;6:30. PMID 29850022
  • Leon LR, Bouchama A. Heat stroke. Compr Physiol. 2015;5(2):611-647. PMID 25880507
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