Definition of Shock
Critical Care Editor: Matthew Alonso, MD; Andrew Cooper, MD
Critical Care Faculty Editor: Todd Rice, MD
Section Editor: Shelby Remmel
Shock is defined as a state of tissue hypoperfusion resulting in cellular and tissue hypoxia and/or organ dysfunction due to reduced oxygen delivery, increased oxygen consumption, inadequate oxygen utilization, or a combination thereof. It most commonly manifests as hypotension; however, it is crucial to recognize that patients with normotension or even hypertension can present in shock.
Shock subtypes
(further characterized in sections below)
- Distributive: Septic, anaphylactic, neurogenic, and rare endocrine emergencies (adrenal crisis, hypothyroidism)
- Cardiogenic: Cardiomyopathy, arrhythmias, severe valvular disease, acute MI
- Hypovolemic: Bleeding, volume depleted states
- Obstructive: PE, tension PTX, cardiac tamponade, constrictive pericarditis
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), associated with tachycardia depending 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 <0.5ml/kg of body weight/hr (or approximately <30 mL/h).
3. Laboratory Abnormalities which indicate abnormal cellular oxygen metabolism and other markers of organ dysfunction, such as lactic acidosis, impaired renal function (AKI), and elevated liver function tests (shock liver).