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volume deficit is functional (decreased effective circulating blood volume) rather
than absolute (see Chapter 86 Cardiac Emergencies ).
TABLE 10.1
CLINICAL CHARACTERISTICS BY TYPE OF SHOCK

Obstructive Shock
An acute mechanical obstruction to ventricular outflow can result in obstructive
shock. Causes include proximal pulmonary embolus, cardiac tamponade, tension
pneumothorax, and obstructive lesions of the left side of heart (hypertrophic left
heart syndrome, aortic coarctation, interrupted aortic arch, and critical aortic
valve stenosis). An acute increase in SVR results from a sudden decrease in
cardiac output and functional hypovolemia. Rapid recognition of the cause of
obstructive shock is critical in order to implement the correct therapy. Congenital
heart lesions typically present at 1 to 3 weeks postnatal age, following closure of
the ductus arteriosus.

Distributive Shock
Distributive shock results from inappropriate vasodilation, pooling of blood in the
peripheral vasculature, and microvascular shunt. Common causes in children are
sepsis, anaphylaxis, and drug ingestions (e.g., atypical antipsychotics). Rarely is
distributive shock present without other types of shock, most notably
hypovolemic shock.