1. Christine A. McKiernan, MD* 2. Stephen A. Lieberman, MD* 1. *Assistant Professor of Pediatrics, Tufts University School of Medicine, Boston, Mass After completing this article, readers should be able to: 1. Review the basic underlying pathophysiology of circulatory shock in children. 2. Characterize the physiologic derangements that occur with the different types of circulatory shock. 3. Discuss the clinical and laboratory manifestations of the acute respiratory distress syndrome and disseminated intravascular coagulation. 4. Review the general supportive measures used for initial stabilization of patients who have circulatory shock. 5. Describe some of the new therapeutic modalities directed at reversing the immunologic abnormalities that are part of the pathogenesis of circulatory failure. For the myriad practitioners who come into contact with critically ill children, the term “shock” has acquired a unique lexicon. For example, a call to our pediatric intensive care unit from a community emergency department physician was highlighted by the comment: “I have a lethargic 3-month-old who looks ‘shocky’ to me.” A frantic page from one of our residents led to this exchange: “We have a 2-year-old down here who is developing diffuse petechiae—she really looks ‘septic’.” A 16-year-old admitted for worsening respiratory distress and an increasing oxygen requirement underwent echocardiography, which was read by the cardiologist as a “moderate-size pericardial effusion with no evidence of either right atrial compression or cardiac tamponade.” Are these physicians talking about different pathophysiologic entities in their respective patients? Not really. Each simply is describing one of the protean manifestations of a diverse and complex syndrome: circulatory shock. The primary function of the cardiovascular system is to provide oxygen and other substrate to the cells. Inextricably linked to this function is the timely and effective removal of the end products of a wide variety of metabolic processes. Circulatory shock or cardiovascular failure ensues when systemic oxygen and nutrient supply become acutely inadequate to meet the metabolic demands of the body’s organ systems. The resulting anaerobic state inefficiently generates intracellular …