• Clinical science



Shock is a life-threatening circulatory disorder that leads to tissue hypoxia and a disturbance in microcirculation. There are many different causes of shock, which are classified into hypovolemic shock (e.g., following massive blood/fluid loss), cardiogenic shock (e.g., as a result of acute heart failure), obstructive shock (e.g., due to cardiac tamponade), and distributive shock (due to redistribution of body fluids), which is further classified into septic, anaphylactic, and neurogenic shock. The common clinical findings are hypotension and abnormal heart frequency (most commonly tachycardia; bradycardia in the case of neurogenic shock) accompanied by specific symptoms related to the cause of shock. Diagnosis is mostly made clinical but measurement of functional parameters (e.g., PCPW, CO, SVR) can help distinguish between the different types of shock. Management of shock involves circulatory support and the treatment of the underlying cause. Shock is associated with a very high mortality rate.



  • Shock: a life-threatening disorder of the circulatory system that results in inadequate organ perfusion and tissue hypoxia, which, in turn, causes metabolic disturbances and, ultimately, irreversible organ damage. [1][2]
  • Shock index = pulse rate/systolic blood pressure
    • > 1 (positive shock index): indicates shock
    • Normal range: 0.4–0.7

Types of shock

Overview of the most common types of shock
Type of shock Hypovolemic Cardiogenic Obstructive Distributive
Septic Anaphylactic Neurogenic
Clinical features
  • Hypotension
  • Tachycardia
  • Weak pulse
  • Cold, clammy extremities
  • Slow capillary refill



  • ↑ or ↓

Cardiac output



(total peripheral resistance)

Systemic vascular resistance


Mixed venous oxygen saturation


  • Decompression

All types of shock, are characterized by low CO and increased SVR, except for septic and anaphylactic shock, which are characterized by high CO and decreased SVR.

General diagnostics

General treatment

  • Monitor blood pressure and heart rate
  • Establish airway, breathing, and circulation (apply high-flow oxygen if necessary)
  • See specific treatment in respective sections below

Stages of shock

  1. Preshock (nonprogressive phase, stage of compensation): activation of compensatory neurohumoral reflexes in order to maintain vital organ perfusion
  2. Shock (progressive phase)
    • Worsening hypotension
    • Hypoperfusion of peripheral tissues → generalized tissue hypoxia anaerobic metabolism in the underperfused organs → lactic acidosis which in turn causes:
      • Worsening tachypnea
      • Precapillary dilation and postcapillary constriction of the blood vessels → pooling and stasis of blood in the capillary bed → decreased cardiac output and formation of microthrombi in the capillaries DIC and further hypoxic injury to tissues
    • Acidosis, cerebral hypoperfusion → altered mental status
  3. End organ dysfunction (irreversible phase, stage of decompensation): irreversible tissue damage sets in

These separate stages may not occur in the case of severe insults (e.g., severe hemorrhage from an abdominal aneurysm, cardiac tamponade). These stages may also not be very distinct in the case of septic shock.

Hypotension, oliguria, tachycardia, and altered mental status indicate that the patient is in shock!

Hypovolemic shock

Classification of hemorrhagic shock
Blood loss < 15% 15–30% 30–40% > 40%
Heart rate 70–99 100–120 120–140 > 140
Systolic blood pressure Normal Normal
Pulse pressure Normal or ↑
Respiratory rate Normal 20–30 30–40 > 35
Urine output > 30 mL/hr 20–30 mL/hr 5–15 mL/hr Absent
Mental status Normal Mildly anxious Anxious, confused Confused, lethargic

Upon suspecting hemorrhage, perform blood grouping and cross-matching and have packed RBC concentrates at hand for transfusion.

Cardiogenic shock

Unlike in other types of shock, the administration of intravenous fluids in most cases of cardiogenic shock worsens cardiogenic pulmonary edema!

Obstructive shock

Distributive shock

Septic shock

Anaphylactic shock

Neurogenic shock

In a patient who develops low blood pressure following high-energy trauma, neurogenic shock is a diagnosis of exclusion that is made after hypovolemic and obstructive shock have been ruled out.

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  • 1. Klabunde RE. Hemorrhagic Shock. http://www.cvphysiology.com/Blood%20Pressure/BP031. Updated April 28, 2014. Accessed May 31, 2018.
  • 2. Drucker WR, Chadwick CD, Gann DS. Transcapillary refill in hemorrhage and shock. Arch Surg. 1981; 116(10): pp. 1344–53. pmid: 7283706.
  • 3. Kaur P, Basu S, Kaur G, Kaur R. Transfusion protocol in trauma. J Emerg Trauma Shock. 2011; 4(1): p. 103. doi: 10.4103/0974-2700.76844.
  • 4. Campbell RL, Li JTC, Nicklas RA, Sadosty AT. Emergency department diagnosis and treatment of anaphylaxis: a practice parameter. Ann Allergy Asthma Immunol. 2014; 113(6): pp. 599–608. doi: 10.1016/j.anai.2014.10.007.
  • 5. Consortium for Spinal Cord Medicine. Early acute management in adults with spinal cord injury: A clinical practice guideline for health-care professionals. J Spinal Cord Med. 2008; 31(4): pp. 403–79. pmid: 18959359.
last updated 11/26/2020
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