Definition of Shock

Critical Care Editor: Hannah Kieffer
Critical Care Faculty Editor: Todd Rice, MD
Section Editor: Jessica Reed

Shock is the clinical syndrome defined by inadequate tissue perfusion and oxygenation leading to cellular and organ dysfunction. 
 

Shock subtypes

(further characterized in sections below)

  • Distributive: Septic, anaphylactic, neurogenic, and rarely endocrine emergencies (adrenal crisis, hypothyroidism)
  • Cardiogenic: Cardiomyopathies, arrhythmias, severe valvular diseases, acute MI
  • Hypovolemic:  Bleeding, volume deplete states
  • Obstructive: PE, tension PTX, cardiac tamponade

Clinical signs of shock and key diagnostic findings

1. Systolic BP <90 mm Hg or mean arterial pressure (MAP) <60 mm Hg for more than 30 minutes (sustained), or the requirement of vasopressors to maintain SBP ≥90 mm Hg or MAP ≥60 mm Hg. Often, but not always, with associated tachycardia pending underlying etiology

2. Clinical signs of tissue hypoperfusion

  • Neurologic: AMS, decreased mentation with possible obtundation, disorientation or confusion
  • Cutaneous: Cool extremities, clammy skin w/peripheral vasoconstriction and cyanosis, and poor cap refill (note: distributive shock often has warm extremities with some signs of vasodilation)
  • Renal: Urine output <30 mL/h or of <0.5ml/kg of body weight/hr

3. Hyperlactatemia (which indicates abnormal cellular oxygen metabolism) and other markers of organ dysfunction such as impaired renal function (AKI), elevated liver function tests (shock liver), and metabolic acidosis

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