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Updated: Dec 17 2021

Distributive Shock

  • Snapshot
    • A 56-year-old man presents after a bee sting half an hour ago. He reports sudden onset of an itchy rash, swelling, and difficulty breathing. His blood pressure is 88/58 mmHg, pulse is 104/min, and respirations are 24/min. On exam, he has swollen lips and generalized erythematous urticarial plaques over his face and chest. There are wheezes audible with each breath. He is given intramuscular epinephrine and fluid bolus. (Anaphylactic shock)
  • Introduction
    • Clinical definition
      • shock secondary to severe peripheral vasodilation
  • Epidemiology
    • Risk factors
      • infection
      • exposure to allergens
      • trauma
  • Etiology
    • Pathogenesis
      • an underlying event (such as infection or anaphylaxis) causes severe peripheral vasodilation → ↓↓ systemic vascular resistance (SVR) → hypotension
      • interruption of autonomic pathways (e.g., from traumatic brain injury) → decreased SVR
      • ↓ SVR → compensatory ↑ cardiac output (CO) initially
        • in severe cases, ↓ CO
    • Septic shock (most common type)
    • non-septic shock
      • systemic inflammatory response syndrome (SIRS) (e.g., burns or air embolism)
      • neurogenic shock (e.g., traumatic brain injury)
      • anaphylactic shock
        • mediated by IgE
      • toxin-induced shock (e.g., snake bites)
      • endocrine shock (e.g., adrenal failure)
  • Presentation
    • Symptoms
      • typically presents with features of the underlying cause (e.g., pneumonia or spinal trauma)
    • Physical exam
      • hypotension
      • warm or dry skin
      • may have fever
  • Studies
    • Labs
      • serum lactate
        • may help guide management in septic shock
    • Pulmonary artery catheterization
      • findings
        • ↓ pulmonary capillary wedge pressure (PCWP < 15 mmHg)
        • ↑ or ↓ cardiac output
        • ↓ systemic vascular resistance
    • Making the diagnosis
      • most cases are clinically diagnosed
  • Differential
      • Different Types of Shock
      • Shock Type
      • Skin
      • Wedge Pressure (PCWP) (Preload)
      • Systemic Vascular Resistance (SVR) (Afterload)
      • Cardiac Output
      • Hyovolemic
      • Cold and clammy skin
      • ↓↓
      • Cardiogenic
      • Obstructive
      • ↑ or ↓
      • ↔ or ↓↓
      • Distributive
      • Warm or dry skin
      • ↔ or ↓
      • ↓↓
      • ↓ or ↑
  • Treatment
    • Management approach
      • treat underlying cause
    • Medical
      • intravenous fluid boluses
        • indications
          • for all patients
      • vasopressors
        • indication
          • for all patients refractory to fluids
          • drugs
            • norepinephrine
              • mechanism of action
                • vasoconstriction of peripheral vessels
              • side effects
                • digital ischemia (due to vasospasm)
                • arrhythmias
            • epinephrine/vasopressin
              • second line vasopressor
            • phenylephrine
  • Complications
    • Death
    • Acute renal failure
  • Prognosis
    • Septic shock is associated with 40-50% mortality rate
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