FIGURE 10.1 Etiologic types of shock The size of each circle is proportional to the incidence of each shock type Although distinct etiologies are evident, there is considerable overlap in the clinical presentation and underlying pathophysiology between categories Blood pressure is determined by both cardiac output and SVR and is generally used as a clinical surrogate for tissue perfusion While low blood pressure will reduce oxygen and nutrient delivery to tissues, the absence of hypotension in children should not be taken to mean that organ perfusion is adequate, since efforts to compensate for changes in cardiac output and SVR may initially preserve blood pressure Early signs of shock with a normal blood pressure, referred to as compensated shock, include tachycardia, mild tachypnea, slightly delayed capillary refill (more than to seconds), cool extremities, orthostatic changes in blood pressure or pulse, decreased urine output, and subtle changes in mental status (e.g., mild irritability or sleepiness) In some cases of distributive shock, such as sepsis or anaphylaxis, a fall in SVR due to peripheral vasodilation may lead to the findings of “bounding” pulses, flash capillary refill, and widened pulse pressure In addition to these clinical signs, biochemical changes such as an