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Syncope (fainting) occurs due to decreased cerebral blood flow resulting in a sudden and brief loss of consciousness and postural tone. If prolonged, may result in seizure and cerebral ischemia.

Causes and types of syncope#

  • peripheral vascular or circulatory compromise
  • vasopressive (often associated with pain and/or stress, gagging, and coughing (posttussive))
  • hypovolemia (orthostatic hypotension)
  • recreational drugs or medications
  • carotid sinus syndrome
  • autonomic dysfunction
  • central nervous system – cerebrovascular (including strokes and transient ischemic attacks), seizure, emotional
  • metabolic – hypoglycemia, anemia, hypoxia, hypercapnea
  • cardiac – obstructive (including thrombotic and embolic events), arrhythmias

Signs and symptoms#


  • nausea
  • warmth
  • perspiration
  • loss of color
  • drop in blood pressure
  • increased pulse (tachycardia)
  • change in sensorium


  • hypotension
  • decreased pulse (bradycardia)
  • increased breathing pattern (hyperpnea)
  • pupillary dilation
  • peripheral coldness
  • visual disturbance
  • seizure activity
  • loss of consciousness

Differential diagnosis#

  • anxiety attack
  • hypoglycemia
  • hypotension
  • hyperventilation
  • myocardial infarction
  • seizure


  • place the patient in the Trendelenburg position (the body is laid flat on the back (supine position) with the feet higher than the head) or left lateral decubitus (on the left side, place a rolled towel under the right hip) for a pregnant women
  • assess consciousness
  • assess Circulation (blood pressure, heart rate), Airway, Breathing
  • administer oxygen, 6-8 L/min by nasal cannula or mask
  • use spirits of ammonia
  • monitor blood pressure, pulse, and respiratory rate
  • place a cold towel on the patient’s forehead
  • if patient is persistently bradycardic (pulse rate <60 beats/minute), administer atropine 0.5mg IV or 1mg IM every 5 minutes until max dose of 3 mg
  • alert emergency medical services (EMS) if loss of consciousness continuous for >5 minutes, or if recovery time is >20 minutes
  • arrange for home escort
  • notify patient’s primary care provider
  • call later to check on patient

Related Pages#