Pediatric emergency medicine trisk 1522 1522
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Many conditions may produce tachycardia ( Table 77.1 ). Most tachycardic
children exhibit sinus tachycardia without significant cardiac pathology ( Table
77.2 ). However, life-threatening conditions frequently come to medical attention
because of fast heart rate and may reflect cardiac and noncardiac origins ( Table
77.3 ).
Sinus Tachycardia
Fever, pain, and emotional arousal (e.g., crying, anxiety) are the most frequent
causes of sinus tachycardia in children. Sympathetic stimulation from other
conditions such as hypoxemia, hypoglycemia, hypercarbia, anemia, and excess
circulating catecholamines (e.g., hyperthyroidism, pheochromocytoma) also
increases sinoatrial node firing rate ( Table 77.2 ). Exogenous sympathomimetic
or anticholinergic substances may cause sinus tachycardia. Over-the-counter
medications that contain antihistamines or pseudoephedrine, “energy” drinks and
diet pills that have high concentrations of caffeine, and commonly abused
substances nicotine (e.g., cigarettes, e-cigarettes/vaping products, gums, patches),
cocaine, amphetamines, methcathinones (e.g., bath salts), or synthetic
cannabinoids (e.g., K2, Spice) are frequently implicated (see Table 63.4 ).
Conversely tachycardia can be a sign of withdrawal from alcohol,
benzodiazepines, or opiates.
Shock is a life-threatening cause of sinus tachycardia that requires rapid
recognition and reversal to prevent permanent organ damage or death (see
Chapter 10 Shock ). Shock may result from intravascular volume loss, inadequate
cardiac contractility, a marked drop in systemic vascular resistance, or a
combination of these mechanisms. History and physical findings help
differentiate the various forms of shock (hypovolemic, cardiogenic, septic, and
distributive) and identify the underlying cause.
Cardiac inflammation associated with viral myocarditis, acute rheumatic fever,
or Kawasaki syndrome frequently presents with sinus tachycardia (see Chapter 86
Cardiac Emergencies ). Patients with these conditions, especially myocarditis, are
also at risk for life-threatening arrhythmias, myocardial ischemia, congestive
heart failure, and/or cardiogenic shock. For patients with pericardial effusion,
sinus tachycardia is a physiologic response to impaired cardiac outflow in order
to maintain cardiac output (see Chapter 86 Cardiac Emergencies ). Pericardial
effusion with tamponade may complicate pericarditis, blunt chest trauma, or
recent cardiac surgery and results in decreased cardiac output with significant
impairment of systemic circulation. In this setting, pericardiocentesis or surgical
pericardiotomy is lifesaving (see Chapter 115 Thoracic Trauma ).
