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KEY CONCEPTS

KEY CONCEPTS

  • imageThe presence of shock is indicated by inadequate global tissue perfusion. Low blood pressures represent states of poor tissue perfusion but are not required to define shock.

  • imageShock is typically classified into one of four etiologic mechanisms: (1) hypovolemic, (2) cardiogenic, (3) obstructive, or (4) vasodilatory/distributive.

  • imageShock syndromes can be differentiated based on evaluation of preload, cardiac output, and afterload or assessment of surrogate markers.

  • imageInadequate oxygen delivery leads to organ damage in critical illness.

  • imageBlood lactate should be measured in all patients in whom shock is suspected.

  • imageTreatment of the patient with circulatory shock can be divided into four phases: salvage, optimization, stabilization, and de-escalation. Each phase has different but sometimes overlapping goals and therapeutic strategies.

  • imageCrystalloid solutions are the first-line fluid of choice for forms of circulatory insufficiency that are associated with hemodynamic instability.

  • imageVasopressors and inotropes are required in patients with shock when volume resuscitation fails to maintain adequate blood pressure and tissues remain hypoperfused.

  • imageThe choice of a particular vasopressor or inotrope agent depends on the underlying shock pathophysiology, goals of therapy, and clinical pharmacology.

  • imageNorepinephrine is the preferred initial vasopressor for shock.

PRECLASS ACTIVITY

Preclass Engaged Learning Activity

Develop a table that has two columns, one titled crystalloid solutions and one titled colloid solutions. In each column, list at least four potential advantages and four potential disadvantages of the solution. Note that there are a number of crystalloid and colloid solutions that are commercially available, so you will need to be specific about the solutions included in the table. The purpose of this exercise is to help students choose a preferred resuscitation fluid for a critically ill patient based on patient-specific data.

INTRODUCTION

Circulatory shock is a medical emergency requiring prompt recognition and treatment because it can quickly lead to serious pathophysiologic consequences, including patient death. Shock is a broad term for a heterogeneous group of syndromes that cause an acute, generalized form of circulatory failure associated with inadequate oxygen utilization by the cells.1 Typically, shock is characterized as a systolic blood pressure (SBP) <90 mm Hg (or acute reduction of at least 40 mm Hg from baseline) or mean arterial blood pressure (MAP) <70 mm Hg with tachycardia and organ perfusion abnormalities.2 The key feature of all shock syndromes is inadequate tissue and organ perfusion.

Learners are strongly encouraged to read Chapter e29 “Evaluation of Cardiovascular Function” and Chapter 137 “Sepsis and Septic Shock” to augment their understanding of the content in this chapter.

EPIDEMIOLOGY

Hemodynamic compromise necessitating vasopressors is common in the intensive care unit (ICU), with about one-third of critically ill patients receiving vasopressors during their clinical course.3 Shock is not a reportable category by state and federal agencies that track causes of death and, thus, the true incidence is unknown. Reported mortality of ...

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