Learn the 3 Medical Meanings of Shock

In first aid, the term "shock" has three distinct definitions:

  1. Noun: a medical condition consisting of too little blood flow to the brain and other vital organs.
  2. Noun: an emotional state of mind, usually following a traumatic event such as a car accident or the loss of a loved one.
  3. Verb: to deliver an electrical charge.
Defibrillator paddles
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Inadequate Blood Pressure

Shock has many causes and in the later stages will usually result in a decreasing blood pressure. When the body is able to maintain the blood pressure even as shock is developing, it is known as compensated shock. Once the blood pressure begins to fall, it becomes uncompensated shock. Uncompensated shock is a severe condition that can be fatal, especially if not treated.

Maintaining blood pressure is a function of the cardiovascular system, which has three distinct parts:

  1. Fluid (blood)
  2. Container vessels (arteries and veins)
  3. Pump (heart)

There are four types of medical shock, which come from a failure of one of the three parts of the cardiovascular system:

  1. Hypovolemic shock develops because of a lack of fluid in the bloodstream. The vessels might still be intact and the pump still works, but the fluid is low. It can be from bleeding directly (hemorrhagic shock) or from other losses of fluid. Dehydration is a common cause of hypovolemic shock.
  2. Distributive shock comes from the container expanding too large for the amount of fluid in the system. This usually occurs from the vessels dilating as a result of a communication failure with the brain (neurogenic shock), or the release of histamines (anaphylactic shock).
  3. Cardiogenic shock is all about the pump. When the heart fails, such as in heart attacks, cardiogenic shock is the result.
  4. Obstructive shock is a special example. This occurs when the flow of blood is blocked by an outside force. One of the most common examples of obstructive shock is ​from a tension pneumothorax (also called a collapsed lung). Air accumulates in the chest outside of the lungs and puts pressure on the heart and other vessels. As the pressure grows, the heart is not able to adequately pump and blood flow is restricted through the vessels that are squeezed.

Some forms of shock combine two or more of the categories. Septic shock is an infection that not only results in dehydration (hypovolemic) but also in vessel dilation (distributive).

Hypoperfusion is a less common medical term that some healthcare providers use to distinguish the medical condition of shock from the emotional state. Hypoperfusion refers to the decreased blood flow of medical shock.

Emotional State

This is probably the most common usage of the term. After a trauma such as a car accident, a person may be quiet and distracted. They are described as being in shock.

Electrical Charge

In certain types of cardiac arrest, shocking the victim can allow the heart to restart and beat normally. An automated external defibrillator (AED) shocks victims of cardiac arrest whose hearts are in ventricular fibrillation.

3 Sources
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  1. Bonanno FG. Clinical pathology of the shock syndromes. J Emerg Trauma Shock. 2011;4(2):233-43. doi:10.4103/0974-2700.82211

  2. Summers RL, Baker SD, Sterling SA, Porter JM, Jones AE. Characterization of the spectrum of hemodynamic profiles in trauma patients with acute neurogenic shock. J Crit Care. 2013;28(4):531.e1-5. doi:10.1016/j.jcrc.2013.02.002

  3. Kolte D, Khera S, Aronow WS, et al. Trends in incidence, management, and outcomes of cardiogenic shock complicating ST-elevation myocardial infarction in the United States. J Am Heart Assoc. 2014;3(1):e000590. doi:10.1161/JAHA.113.000590