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This article is about medicine. For the concept of shock in physics and mechanics, see Shock (mechanics).

In medicine, shock is a life-threatening medical emergency characterized by inability of the body to supply enough oxygen to meet tissue requirements. Most causes of shock result in a reduced cardiac output. Shock may rapidly progress to death without medical intervention.

Table of contents
1 Types of shock
2 Symptoms and signs
3 Treatment
4 Prognosis

Types of shock

The commonest causes of shock is blood loss leading to hypovolemic shock. It is necessary to immediately control bleeding and restore the victims blood volume by giving intravenous fluids and, possibly, blood transfusions.

Cardiogenic shock is caused by the failure of the heart to pump effectively. This can be due to damage to the heart muscle, most often from a large myocardial infarction. Other causes of cardiogenic shock include cardiac tamponade, arrhythmiass, or cardiac valve problems.

Septic shock is caused by overwhelming infection leading to vasodilation. Despite a geneerally increased cardiac output the body is unable to meet the demand for oxygen. It is treated by antibiotics, fluid replacement, and vasoconstrictors.

Less commonly severe anaphylactic reactions may cause anaphylactic shock as allergens trigger widespread vasodilation and movement of fluid out of the blood into the tissues.

The rarest cause of shock, thankfully, is acute spinal cord injury leading to neurogenic shock. Neurogenic shock is caused by the sudden loss of the sympathetic nervous system signals to the smooth muscle in vessel walls. Without this constant stimulation the vessels relax resulting in a sudden decrease in peripheral vascular resistance and decreased blood pressure.

Symptoms and signs

The signs and symptoms of shock include pallor, rapid heart rate, rapid breathing, decreased urine production and confusion or anxiety. Because of the bodies reflex responses low blood pressure is a late sign.

Patients with hypovolaemic or cardiogenic shock will have cold and clammy hands and feet. Septic, anaphylactic and neurogenic shock may present with warm extremities.


Shock is a medical emergency. First aid treatment includes calling for help, controlling any external bleeding and giving oxygen if it is available. CPR may be neccessary.

Most patients will need intravenous access for administration fluids and drugs. Some patients, especially those with reduced levels of consciousness, require immediate intubation and mechanical ventilation.

Specific treatment depends on the cause.


The prognosis of shock depends on the underlying cause and the nature and extent of concurrent problems.

Hypovolaemic, anaphylactic and neurogenic shock are readily treatable and respond well to medical therapy. Septic shock however, is a grave condition and with a mortality rate between 30% and 50%. The prognosis of cardiogenic shock is even worse.

Shock is said to evolve from reversible to irreversible. This clinical distinction is generally only made retrospectivly. Most cases of untreated reversible shock progress to irreversible shock within six hours due to hypoxic tissue damage.