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For further information, see CMDT Part 12-19: Shock

Key Features

Essentials of Diagnosis

  • Hypotension, tachycardia, oliguria, altered mental status

  • Peripheral hypoperfusion and impaired oxygen delivery

General Considerations

  • Can be classified as

    • Hypovolemic

    • Cardiogenic

    • Obstructive

    • Distributive, including septic, neurogenic, and endocrine


  • Results from decreased intravascular volume secondary to loss of blood or fluids and electrolytes

  • 15% loss of intravascular volume can result in hypotension and progressive tissue hypoxia


  • Results from cardiac failure with the resultant inability of the heart to maintain adequate tissue perfusion

  • Clinical definition: evidence of tissue hypoxia due to decreased cardiac output (cardiac index < 2.2 L/min/m2) in the presence of adequate intravascular volume

  • Most often caused by myocardial infarction but can also be due to cardiomyopathy, myocardial contusion, valvular incompetence or stenosis, or arrhythmias


  • Results from acute decrease in cardiac output due to pericardial tamponade, tension pneumothorax, or massive pulmonary embolism


  • Causes include sepsis (most common), anaphylaxis, traumatic spinal cord injury, or acute adrenal insufficiency

  • Reduction in systemic vascular resistance (SVR) results in inadequate cardiac output and tissue hypoperfusion despite normal circulatory volume

  • Septic

    • Clinically defined as

      • Sepsis with fluid-unresponsive hypotension (systolic blood pressure < 100 mm Hg)

      • Serum lactate level > 2 mmol/L

      • Needing vasopressors to maintain mean arterial pressure > 65 mm Hg

    • Gram-positive or gram-negative organisms most common cause

    • Polymicrobial infections are almost as likely

    • Incidence of sepsis caused by fungal organisms is increasing, but remains less than that for bacterial infections

    • Risk factors

      • Bacteremia

      • Extremes of age

      • Diabetes

      • Cancer

      • Immunosuppression

      • History of a recent invasive procedure

    • Sequential Organ Failure Assessment (SOFA) scoring system

    • Quick SOFA (qSOFA) scoring system

      • See

      • 1 point each is assigned for hypotension (systolic blood pressure < 100 mm Hg), altered mental status, or tachypnea (respiratory rate (RR) ≥ 22 breaths per minute)

      • A qSOFA score of 2 or more in a patient with suspected infection suggests worsened clinical outcomes and may influence triage decisions for ICU-level care

  • Systemic inflammatory response syndrome (SIRS)

    • Defined as a systemic response to a nonspecific infectious or noninfectious insult—such as burns, pancreatitis, an autoimmune disorder, ischemia, or trauma

    • The presence of two or more of the following clinical criteria help establish the diagnosis of SIRS

      • Body temperature > 38oC (100.4oF) or < 36oC (96.8oF)

      • Heart rate > 90 beats per minute

      • Respiratory rate more than 20 breaths per minute or hyperventilation with an arterial carbon dioxide tension (PaCO2) < 32 mm Hg

      • Abnormal white blood cell count (> 12,000/mcL or < ...

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