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 to 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