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LEARNING OBJECTIVES
Upon completion of the chapter, the reader will be able to:
List the most common conditions resulting in the following circulatory shock syndromes: hypovolemic, cardiogenic, and obstructive.
Describe the major hemodynamic and metabolic abnormalities that occur in patients with circulatory shock.
Describe the clinical presentation including signs, symptoms, and laboratory test measurements for the typical circulatory shock patient.
Prepare a treatment plan with clearly defined outcome criteria for hypovolemic, cardiogenic, and obstructive shock patients, including fluid management, pharmacologic therapy, and/or surgical/mechanical interventions.
Compare and contrast relative advantages and disadvantages of crystalloids, colloids, and blood products in treating hypovolemic shock.
Formulate a stepwise monitoring strategy for patients with hypovolemic, cardiogenic, and obstructive shock.
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The primary function of the circulatory system is to supply oxygen and vital metabolic compounds to cells throughout the body, as well as remove metabolic waste products. Circulatory shock is a life-threatening condition whereby this principal function is compromised, resulting in inadequate cellular oxygen utilization.1,2 While septic shock also has a cardiovascular component to its manifestation, it will not be addressed in this chapter based on its unique presentation involving the systemic inflammatory response. Instead, this shock state is addressed as a component of Chapter 84, “Sepsis and Septic Shock” within this textbook. Furthermore, less common shock states such as anaphylactic and neurogenic shock will not be addressed in this chapter. 
When circulatory shock is caused by a severe loss of blood volume or body water, it is called hypovolemic shock. Cardiogenic shock can be thought of as “pump failure.” It most often follows an acute myocardial infarction and less commonly, end-stage heart failure, advanced valvular disease, or cardiac arrhythmias.2,3 Obstructive shock limits adequate heart functioning mechanically, usually due to a massive pulmonary embolism, cardiac tamponade, tension pneumothorax, or abdominal compartment syndrome.4 These three shock states share the commonality of decreased blood flow.5 Rapid and effective restoration of circulatory homeostasis using fluids and/or blood products, pharmacologic agents, and/or surgical/mechanical interventions is imperative to prevent complications of untreated shock and, ultimately, death following circulatory shock.
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ETIOLOGY AND EPIDEMIOLOGY
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The most common type of shock is septic shock, accounting for over 60% of cases in a large shock trial. In this same trial, cardiogenic, hypovolemic, and obstructive shock accounted for 16%, 16%, and 2% of enrolled patients, respectively.6 The prognosis of shock patients depends on several variables, including type, severity, duration, underlying etiology, preexisting organ dysfunction, and reversibility.5 For example, overall mortality rates may approach 50% in cardiogenic shock patients,7 while hypovolemic shock due to hemorrhage is a major factor in trauma deaths, with an estimated 1.9 million deaths per year worldwide.8
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Practitioners must have a good understanding of cardiovascular physiology to diagnose, treat, and monitor circulatory problems in critically ill patients. The interrelationships among ...