Heat syncope

Background

• Variant of postural hypotension
  • Results from combination of volume depletion, decreased vasomotor tone and peripheral vasodilatation
  • Occurs in nonacclimatized patients during early stages of heat exposure (especially elderly)

Diagnosis

• Diagnosis of exclusion

Differential Diagnosis

Environmental heat diagnoses

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

Syncope Causes

• Cardiovascular-mediated syncope
  • Dysrhythmias:
    • WPW (pre-excitation)
    • Long QT Syndrome/QT prolongation
    • Brugada Syndrome
    • Catecholaminergic polymorphic ventricular tachycardia
    • 2nd/3rd AV Block
    • Afib/aflutter
    • Vtach/torsades
    • Sick sinus syndrome
    • Arrhythmogenic right ventricular dysplasia
    • Short QT syndrome
  • Cardiovascular disease
    • Valvular Disease (AS, MS, tricuspid stenosis)
    • Aortic Dissection
    • Myocardial Infarction
    • CHF
    • Hypertrophic Cardiomyopathy
    • PE
    • Pericardial Tamponade
    • Myxoma
    • Pulmonary Hypertension
    • Pacemaker malfunction
• Neurally mediated syncope
  • Vasovagal:
    • Fear, pain, emotion, valsalva, breath-holding spell
  • Situational (associated with):
    • Coughing, micturition, defecation, vomiting, swallowing, postexercise
    • Carotid sinus stimulation
• Orthostatic hypotension-mediated syncope:
  • Volume depletion:
    • Dehydration (vomiting, diarrhea)
    • Hemorrhage, (Ectopic Pregnancy, Upper GI Bleed/Lower GI Bleeding, Abdominal Aortic Aneurysm)
    • Sepsis
  • Autonomic Dysreflexia
  • Autonomic failure due to meds
• Other serious causes
  • Stroke
  • SAH
  • TIA
  • Vertebrobasilar Insufficiency
  • Subclavian steal
  • Heat syncope
  • Hypoglycemia
  • Hyperventilation
  • Asphyxiation
  • Seizure
  • Narcolepsy
  • Psychogenic (anxiety, conversion disorder, somatic symptom disorder)
  • Toxic (drugs, carbon monoxide, etc.)

Management

• Remove pt from heat source
• Give PO or IV rehydration

Disposition

• Hospitalization usually not necessary

See Also

• Heat Emergencies

Source

Waters T. Heat Emergencies In: Tintinalli's Emergency Medicine: A Comprehensive Study Guide. 7th ed. McGraw Hill Medical. 2011: 1339