Pediatric emergency medicine trisk 376

eFIGURE 75.1 Lateral neck radiograph of a child with epiglottitis. Note the swollen epiglottis,
often referred to as the “thumb sign” (arrow ) and ballooning of the hypopharynx (A ).


eFIGURE 75.2 Lateral neck radiograph of a child with a retropharyngeal abscess. Note the
widened prevertebral/retropharyngeal space (A ).


CHAPTER 76 ■ SYNCOPE
THOMAS B. WELCH-HORAN, ROHIT SHENOI

INTRODUCTION
Syncope is a sudden, brief loss of consciousness and postural tone caused by
transient global cerebral hypoperfusion and characterized by complete recovery.
Presyncope is a feeling of impending sensory and postural changes without loss
of consciousness. Syncope is a common condition in childhood. In the United
States, it accounts for about 3% of pediatric emergency department (ED) visits.
The incidence peaks during the second decade of life, and about 30% to 50% of
children experience syncope by the end of adolescence. Girls are more commonly
affected than boys. The most common cause of syncope in children is vasovagal
syncope, which is related to a loss of vasomotor tone and is generally benign.
Occasionally, the etiology may be a life-threatening cardiac condition. When
evaluating a child who presents to the ED with syncope, the goal is to assess
whether high-risk conditions are present, or whether the symptoms can be
attributed to a more benign etiology.
When normal individuals assume an upright position, cardiac output and
cerebral arterial blood pressure (BP) are maintained by a combination of
mechanical pumping activity of the skeletal muscles on venous return to the right
atrium, the presence of one-way valves in the veins that facilitate venous return,
arterial vasoconstriction caused by the baroreceptor reflex, and cerebral blood
flow autoregulation. If stroke volume is not maintained, then reflex sinus

tachycardia develops. Vasovagal syncope (also known as neurocardiogenic
syncope) is believed to begin with excessive peripheral venous pooling that leads
to a sudden decrease in peripheral venous return. This results in increased cardiac
contractility and baroreceptor and left ventricular mechanoreceptor firing,
followed by an efferent response consisting of peripheral α-adrenergic withdrawal
and enhanced parasympathetic tone. The hallmark is vasodilatation and
bradycardia with hypotension. Sudden activation of a large number of
mechanoreceptors in the bladder, rectum, esophagus, and lungs may also provoke
such a response. In orthostatic hypotension, often caused by fluid depletion, the
compensatory responses and ensuing sinus tachycardia are insufficient to
maintain brain perfusion, and syncope develops when the patient stands.
Syncope on exertion suggests a cardiac or cardiopulmonary cause, such as
obstruction to left or right ventricular outflow or pulmonary hypertension. In


these conditions, cardiac output is unable to meet increased peripheral tissue
needs. Failure to increase cardiac output sufficiently, together with a fall in
peripheral resistance during exercise, may lead to syncope on exertion. There are
three main categories of syncope: autonomic (vasovagal or neurocardiogenic),
cardiac, and others ( Table 76.1 ).

AUTONOMIC (VASOVAGAL OR NEUROCARDIOGENIC)
SYNCOPE
Autonomic syncope is the most common cause of syncope in children and
adolescents, and accounts for almost 80% of cases. It belongs to a group of
neurally mediated syncope conditions in which there is a brief inability of the
autonomic nervous system to keep BP and sometimes heart rate at a level
necessary to maintain cerebral perfusion and consciousness. Other conditions in
this group include “situational” syncope, which may occur after micturition,
defecation, hair grooming, coughing, or sneezing. The precipitating causes for

vasovagal syncope include prolonged standing, a crowded and poorly ventilated
environment, brisk exercise in a warm environment, severe anxiety, perceived or
real pain, and fear. There are three clinical types. In the first, there is marked
hypotension (vasodepressor syncope). The second type is characterized by
marked bradycardia (cardioinhibitory syncope) and in the third form, there is a
combination of hypotension and bradycardia. Some symptoms that herald a
syncopal event include feelings of weakness, lightheadedness, blurring of vision,
diaphoresis, and nausea.
Breath-holding spells, a type of vasovagal syncope, occur in older infants and
toddlers and may be triggered by anger, pain, or fear. There are two forms:
cyanotic or pallid. In the cyanotic form, the child holds his or her breath, turns
cyanotic, and then loses consciousness. In the pallid form, the loss of
consciousness occurs before breath-holding. Occasionally the child may have
associated tonic or clonic motor activity.

CARDIAC SYNCOPE
There are several cardiac conditions that can lead to syncope in children ( Table
76.1 ). They account for 1.5% to 6% of pediatric syncope. The most important
causes that may be associated with significant morbidity or death are discussed
here.

Long QT Syndrome (LQTS)
This is an important cause of syncope and sudden cardiac death in children
without structural heart disease. An abnormal electrocardiogram (ECG) obtained