Heat stroke: Difference between revisions

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==Background==
==Background==
*Universally fatal if left untreated
*Severe, life-threatening end of the [[heat emergencies|heat illness]] spectrum
*Types
*Defined as core temperature >40°C (104°F) with CNS dysfunction
**Classic (nonexertional)
*'''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>
***Seen in children and elderly
*Mortality directly correlates with duration and degree of elevated core temperature
**Exertional
*Hallmark is multisystem organ dysfunction from heat-induced systemic inflammatory response
***Seen in otherwise young, healthy individuals
 
===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==
==Clinical Features==
*Heat exposure + elevated temperature >40C (>104F) + neurologic abnormalities:
*Core temperature >40°C (104°F) PLUS
**Inappropriate behavior
*CNS dysfunction<ref>Becker JA, Stewart LK. Heat-related illness. ''Am Fam Physician''. 2011;83(11):1325-30. PMID 21661715</ref>:
**[[Confusion]]
**Altered mental status, confusion, agitation, slurred speech
**[[Delirium]]
**Ataxia, [[seizures]], coma
**[[Ataxia]]
**Inappropriate behavior may be earliest sign
**[[Coma]]
*Anhidrosis is frequently present but its absence does NOT rule out heat stroke
**[[Seizures]]
**Sweating may still be present, especially in exertional heat stroke
*Anhidrosis is frequently present; however, its absence does NOT rule out heat stroke
*Tachycardia, [[hypotension]] (high-output state → eventual cardiovascular collapse)
**Symptoms seen in [[Heat Exhaustion]] may also be present
*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==
===Environmental===
{{Altered mental status and fever DDX}}
{{Template:Heat Emergencies}}
{{Environmental heat illness DDX}}


===Non-Environmental===
*Key diagnoses to consider:
*Infectious
**[[Sepsis]] / [[meningitis]] / [[encephalitis]]
**[[Sepsis]]
**[[Thyroid storm]]
**[[Meningitis]]
**[[Neuroleptic malignant syndrome]]
**[[Encephalitis]]
**[[Malaria]]
**[[Typhoid]]
**[[Tetanus]]
*Endocrine
**[[Thyroid Storm]]
**[[Pheochromocytoma]]
**[[DKA]]
*Neurologic
**Hypothalamic bleeding or infarct
**[[CVA]]
**[[Status epilepticus]]
*Toxicologic
**Anticholinergic toxidrome
**[[Sympathomimetic overdose]]
**[[Salicylate overdose]]
**[[Serotonin syndrome]]
**[[Serotonin syndrome]]
**[[Malignant hyperthermia]]
**[[Malignant hyperthermia]]
**[[Neuroleptic Malignant Syndrome]]
**[[Anticholinergic toxicity]]
**Withdrawal (ETOH, benzo)
**Sympathomimetic toxicity ([[cocaine]], [[amphetamines]])
**[[Alcohol withdrawal]] / [[benzodiazepine withdrawal]]


{{AMS and fever 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<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


==Diagnosis==
==Management==
*Blood sugar
===Immediate===
*CBC
*Cooling is THE priority — every minute of delay increases mortality
*Chemistry
*Remove from hot environment; remove clothing
*VBG
*Address ABCs; intubate if necessary for airway protection
**PaCO2 is often <20 2/2 hyperventiltaion
*Goal: reduce core temperature to 39°C (102.2°F) within 30 minutes
**Exertional heat stroke often results in lactic acidosis
*Cooling rate target: 0.15-0.25°C/min
*Coags
*CK
*UA
*[[ECG]]
*CXR
*?CT/[[LP]]


==Treatment==
===Rapid Cooling Techniques===
===General===
====Cold Water Immersion (Treatment of Choice)====
*IVF
*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>
**Initiate at a rate that ensures adequate (start w/ NS 250cc/hr)
*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


===Cooling===
====Evaporative/Convective Cooling====
*Goal is to reduce temp to 39C (102.2F) and then stop to avoid overshoot hypothermia
*Spray lukewarm water (15°C / 59°F) continuously on patient while directing fans at exposed skin
*Antipyretics (ASA and acetaminophen) and dantrolene have no role
*Easier to apply while performing other interventions in ED
*Cooling blankets work too slowly to be employed as sole treatment
*Slower cooling rate than immersion
*Ice packs to neck, axillae, groin are useful as adjunct only
 
*Cold IVF is not effective
====Other Techniques====
*Techniques
*Cold IV fluids (4°C NS bolus) as adjunct (limited cooling on its own)
**Evaporative
*Ice packs to entire body surface (better than just neck/axillae/groin)
***Method of choice
**Ice packs only to neck, axillae, groin provides minimal cooling
***Spray cool water (15C (59F)) on most of pt's body surface; turn on fan
*Invasive lavage (bladder, gastric, thoracic) — limited data, reserved for refractory cases
***Complications
*ECMO — for refractory heat stroke
****Shivering (occurs when skin temp is <30C (86F): tx w/ short-acting benzos
 
****Electrodes not sticking: place on pt's back instead
===What NOT to Do===
**Ice-water immersion
*NO antipyretics (acetaminophen, NSAIDs) — thermoregulatory set point is normal; these are ineffective and may worsen liver/renal injury
***Consider especially in young, healthy pts
*NO dantrolene — not effective in heat stroke (heat stroke is not malignant hyperthermia)
***Complications
*AVOID peripheral vasoconstrictors (norepinephrine) — may redirect blood from skin and impair cooling
****Shivering
*AVOID shivering (counterproductive) — treat with benzodiazepines if occurs during cooling
****Inability to perform defibrillation or resuscitative procedures
 
**Invasive
===Supportive Care===
***Consider if evaporative cooling / immersion is insufficient
*IV fluid resuscitation:
***Examples: cold water gastric lavage, bladder lavage, rectal lavage
**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==
==Complications==
*[[Hypotension]]
*Hepatic injury: almost always present; usually reversible but can progress to fulminant failure
**BP will usually respond to small fluid bolus (500cc) and body cooling
*[[Rhabdomyolysis]] → [[acute kidney injury]] (more common in exertional)
***If ineffective consider pressors (dopamine or dobutamine)
*[[DIC]] and abnormal bleeding
*[[Electrolyte abnormalities]]
**Variable: hypokalemia and hyper or hyponatremia may be seen
*Hematologic
**[[DIC]] or abnormal bleeding
*Renal failure
*[[ARDS]]
*[[ARDS]]
*[[Seizure]]
*Persistent neurologic deficits: present in ~20% of survivors, associated with high mortality
**Treate with [[benzos]]
*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==
==See Also==
*[[Heat Emergencies]]
*[[Heat emergencies]]
*[[Heat Exhaustion]]
*[[Heat exhaustion]]
*[[Acute Fever (DDX)]]
*[[Rhabdomyolysis]]
*[[Malignant hyperthermia]]
*[[Neuroleptic malignant syndrome]]


==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:Environ]]
[[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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