Updated: 7/29/2021

Distributive Shock

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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
    • 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)
  • 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
  • Prognosis
    • septic shock is associated with 40-50% mortality rate
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
 
 

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