Syncope is a loss of consciousness related to decreased cerebral perfusion to the areas of the brain necessary for consciousness, which include the brainstem, reticular activating system, and the bilateral cerebral cortices. International incidence was reported in 126 of the 100,000 children monitored, with peak incidence between the ages 15 to 19. Neurocardiogenic syncope and neurologic disorders were the most common etiologies, representing 80% and 9%, respectively. Other causes included psychological, cardiac, respiratory, toxicologic, and metabolic problems (Table 118.1). Neurocardiogenic and disease-related syncope were easily identified or suspected by history and physical examination.

Vasovagal syncope may be characterized by the sudden loss of vasomotor tone with resultant systemic hypotension (the vasodepressor response), accompanied by significant bradycardia or asystole, known as the cardioinhibitory response. Most episodes occur when the patient is in the upright position, either during a prolonged period of standing (such as in church, gym/military drill), or during the rapid change from supine or sitting position to standing. There may be an emotional component and symptoms often occur in the setting of fatigue, hunger, concurrent illness, and dehydration. The loss of consciousness typically lasts <1 to 2 minutes.