The Causes of Different Types of Shock

There are four categories of shock

In the medical field--especially emergency medical services--shock has three meanings: it can be an electrical discharge, an emotional state, or a life-threatening condition. For the purposes of this article, we're going to focus on the stuff that can kill you. 

Trouble Filling the Capillaries

Regardless of the type of shock, it all has one commonality: shock interferes with the body's ability to get blood into all the tissues. In order to adequately perfuse (infuse with blood) the body's tissues, there has to be enough blood being pumped around the closed system (blood vessels, including capillaries) with enough force (pressure) to push tiny little red blood vessels single file into the capillary beds.

At its heart, shock is a lack of adequate blood pressure. 

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 cardiovascular system:


MERT Deliver Casualties At The Camp Bastion Hospital
Bleeding is the most common cause of hypovolemic shock. Marco Di Lauro / Getty Images

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.

Hypovolemic shock can be from bleeding directly (hemorrhagic shock) or from other losses of fluid. Dehydration is a common cause of hypovolemia, as is sepsis (which also causes distributive shock).


Epinephrine injector for allergy.
Epinephrine injector for anaphylaxis. mario loiselle / Getty Images

Distributive shock comes from the container (blood vessels) expanding too large for the amount of fluid in the system. The amount of blood in the system can be low or normal, but the blood vessels expand too large to maintain adequate pressure.

Distributive shock usually occurs from the vessels dilating as a result of a communication failure with the brain (neurogenic shock from a spinal cord injury, for example) or the release of histamines (anaphylactic shock).


woman collapsed in fatigue
Fatigue is a symptom of heart attack. Macduff Everton / Getty Images

Cardiogenic shock is all about the pump. When the heart fails, such as in heart attacks, cardiogenic shock is the result.

Congestive heart failure is an example of cardiogenic shock. Congestive heart failure is a back up of blood into the body or into the lungs as a result of one side of the heart being damaged from a heart attack. The good side of the heart pumps at full speed while the damaged side can't keep up and blood pressure suffers as a result.


x-ray of pneumothorax
Tension pneumothorax is an example of obstructive shock. 33karen33 / Getty Images

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.

The other common example of obstructive shock is from pericardial tamponade. The sac around the heart (pericardium) traps blood between it and the heart inside it. The trapped blood begins to exert pressure on the heart and squeezes it hard enough to slow blood flow.

Combinations of Shock Types

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

Trauma to the chest often results in not only a tension pneumothorax (obstructive) but also in severe bleeding (hypovolemic or, if you prefer to be very specific, hemorrhagic shock).


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.