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

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 pericardial tamponade, tension pneumothorax, or massive pulmonary embolism

Distributive

• 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

    • See https://en.wikipedia.org/wiki/SOFA_score

    • An increase of 2 or more SOFA score points in a patient with infection is diagnostic of sepsis with a predicted 10% mortality

  • Quick SOFA (qSOFA) scoring system

    • See https://en.wikipedia.org/wiki/SOFA_score

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

    • 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 < ...