Heat stroke

Background

• Universally fatal if left untreated
• Types
  • Classic (nonexertional)
    • Seen in children and elderly
  • Exertional
    • Seen in otherwise young, healthy individuals

Clinical Features

• Heat exposure + elevated temperature >40C (>104F) + neurologic abnormalities:
  • Inappropriate behavior
  • Confusion
  • Delirium
  • Ataxia
  • Coma
  • Seizures
• Anhidrosis is frequently present; however, its absence does NOT rule out heat stroke
  • Symptoms seen in Heat Exhaustion may also be present

Differential Diagnosis

Environmental heat diagnoses

• Heat cramps
• Heat edema
• Heat exhaustion
• Heat tetany
• Heat stroke
• Heat syncope
• Miliaria
• Hyperthermia

Non-Environmental

• Infectious
  • Sepsis
  • Meningitis
  • 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
  • Malignant hyperthermia
  • Neuroleptic Malignant Syndrome
  • Withdrawal (ETOH, benzo)

Altered mental status and fever

• Infectious
  • Sepsis
  • Meningitis
  • Encephalitis
  • Cerebral malaria
  • Brain abscess
• Other
  • Neuroleptic malignant syndrome
  • Serotonin syndrome
  • Malignant hyperthermia
  • Sympathomimetic toxicity (cocaine, amphetamine, ketamine)
  • Anticholinergic toxicity
  • Heat stroke
  • Delirium tremens
  • Hypothalamic stroke
  • Pheochromocytoma
  • Thyroid storm

Diagnosis

• Blood sugar
• CBC
• Chemistry
• VBG
  • PaCO2 is often <20 2/2 hyperventiltaion
  • Exertional heat stroke often results in lactic acidosis
• Coags
• CK
• UA
• ECG
• CXR
• ?CT/LP

Treatment

General

• IVF
  • Initiate at a rate that ensures adequate (start w/ NS 250cc/hr)

Cooling

• Goal is to reduce temp to 39C (102.2F) and then stop to avoid overshoot hypothermia
• Antipyretics (ASA and acetaminophen) and dantrolene have no role
• Cooling blankets work too slowly to be employed as sole treatment
• Ice packs to neck, axillae, groin are useful as adjunct only
• Cold IVF is not effective
• Techniques
  • Evaporative
    • Method of choice
    • Spray cool water (15C (59F)) on most of pt's body surface; turn on fan
    • Complications
      • Shivering (occurs when skin temp is <30C (86F): tx w/ short-acting benzos
      • Electrodes not sticking: place on pt's back instead
  • Ice-water immersion
    • Consider especially in young, healthy pts
    • Complications
      • Shivering
      • Inability to perform defibrillation or resuscitative procedures
  • Invasive
    • Consider if evaporative cooling / immersion is insufficient
    • Examples: cold water gastric lavage, bladder lavage, rectal lavage

Complications

• Hypotension
  • BP will usually respond to small fluid bolus (500cc) and body cooling
    • If ineffective consider pressors (dopamine or dobutamine)
• Electrolyte abnormalities
  • Variable: hypokalemia and hyper or hyponatremia may be seen
• Hematologic
  • DIC or abnormal bleeding
• Renal failure
• ARDS
• Seizure
  • Treate with benzos

See Also

• Heat Emergencies
• Heat Exhaustion
• Acute Fever (DDX)