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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 and neurogenic

  • Hypovolemic

    • 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

  • Cardiogenic

    • 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

  • Obstructive

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

  • Distributive

    • Causes include sepsis (most common), anaphylaxis, systemic inflammatory response syndrome produced by severe pancreatitis or burns, 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

    • 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 < 4000/mcL or > 10% immature [band] forms)

      • When a source of infection is confirmed, SIRS is categorized as sepsis

    • Neurogenic

      • Caused by traumatic spinal cord injury or effects of an epidural or spinal anesthetic agent

      • Reflex vagal parasympathetic stimulation evoked by pain, gastric dilation, or fright may simulate neurogenic shock, producing hypotension, bradycardia, and syncope

Clinical Findings

Symptoms and Signs

  • Hypotension

  • Weak or thready peripheral pulses

  • Cold or mottled extremities

  • Splanchnic vasoconstriction may lead to oliguria, bowel ischemia, and hepatic dysfunction

  • Mentation may be normal or altered (eg, restlessness, agitation, confusion, lethargy, or coma)

  • Hypovolemic

    • Jugular venous pressure is low

    • Narrow pulse pressure indicative of reduced stroke volume

  • Cardiogenic

    • Jugular venous pressure is elevated

    • Global hypoperfusion with oliguria


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