Shock: Medical Definition, Causes, Types and Stages

Shock: Medical Definition, Causes, Types and Stages
Photo source: Getty images

Shock - informally, this term is mostly used to indicate a stress response. However, in medicine, it has a completely different meaning. It indicates a condition where a person is acutely at risk to health and life.


We usually use the word shock in its colloquial form to describe a situation in an acute stress response. However, in medicine, it has a completely different meaning and does not express a person's mental state.

What does shock mean in medicine?
What could be the cause?
What types and stages of shock do we know?
How does it manifest itself?

Shock refers to the body's overall response, which occurs for several reasons. The shock condition affects various body systems and manifests itself in a variety of symptoms. It endangers a person's health and life.

What is a Shock? How is it Defined?

When looking for a definition of shock, we can come across several forms. Their essence is the same, only the way of expression changes.

Shock is...


... a disproportion between the need and supply of oxygen and nutrients for the body.


... a life-threatening condition based on a disorder of the blood supply to cells, tissues and organs. If left untreated, organs and organ systems gradually fail. It affects vital organs, such as the brain, heart or kidneys and lungs.


... is an acute, i.e. sudden, or even subacute change in macrocirculation and microcirculation, which is manifested by reduced blood flow to tissues and organs. There is insufficient oxygen and nutrients in the cells. Toxic metabolic or metabolite products accumulate in them.

Hypoxia - the body or a region of the body is deprived of adequate oxygen supply at the tissue level.

Subsequently, it progresses to a malfunction of the cells, organs and finally the entire organ systems. In case of treatment delay, it goes into an irreversible, ie irreversible phase. Damage to the brain, heart, kidneys and other organs occurs.

The fcondition ends in the death of the victim.


... is a severe dynamic condition in which the supply of oxygen to the tissues of vital organs is insufficient for their current energy requirements.

Excess post-exercise oxygen consumption, informally called afterburn or "oxygen debt", occurs and metabolic acidosis develops.

Learn more on acidosis and alkalosis in the article Acidification is nonsense.

The cause is a disparity between the size of the vascular circulatory system and the amount of blood, i.e. fluids in the bloodstream.

Doctor in shock
The doctor is not shocked by shock. Photo: Getty images

The 3 Phases of Shock

The shock is said to be a dynamic state because it goes through several stages. This division is especially important from the point of view of treatment.

The shock has three phases, which are also referred to as compensatory shock, decompensated shock, and refractory shock. The transition from one phase to another is dynamic and the speed depends on several factors.

The rate of shock development depends on:

  1. the state of the organism at the time of the acute change
  2. age
  3. comorbidities
  4. immunity
  5. coagulation
  6. CNS - central nervous system
  7. mental state
  8. the extent of the cause
  9. the time of the event
  10. the presence of negative factors, such as fatigue or hypothermia

Table: Individual phases of shock

Shock phase Technical description
Compensatory Compensatory shock
  • the organism adapts to a sudden, ie acute change
  • circulation is centralized
  • efforts to maintain blood supply to essential vital organs
    • brain, heart, adrenal glands (for the production of adrenaline and norepinephrine)
  • other tissues and organs are congested to a lesser extent
    • kidneys, lungs, muscles, skin, spleen
  • accelerated breathing
  • accelerated heart rate, frequency, pulse
  • cardiac contraction - blood expulsion - systole increases
Decompensated Decompensated shock
  • after exhaustion of the compensation mechanisms
  • dilatation of the bloodstream - the blood vessels dilate
  • as a result, blood pressure drops
  • the fluid permeability of the vessels increases
  • it passes from the vessels to the out of the vascular space
  • exacerbates the pressure drop
  • which reduces the blood supply to vital organs
  • bloodless and damaged cells wash out toxic substances, metabolites, enzymes
  • these substances adversely affect heart function
  • the risk of Disseminated intravascular coagulation (DIC)
  • and MODS - Multiple organ dysfunction syndrome
Refractory Terminal phase, i.e. final, irreversible
  • permanent damage to cells, tissues and organs
  • dysfunction of organ systems MODS + DIC
  • failure of vital signs
  • or death

Necrosis, i.e. cell decay = cell death.
If cell death affects a certain number of cells of vital organs...
...eliminating the root cause of the shock will not help either.  
The essence of the irreversible phase of shock.


The shock arises due to the disparity between the supply and the need for oxygen and nutrients.

And plus, for impaired drainage of toxic substances that arise during metabolism and impaired function from cells.

Blood vessels, blood, red blood cells
The blood carries oxygen and nutrients to the organs - it is pumped by the heart. Photo: Getty images

There may be various causes of shock.

1. The reason may be the loss of fluids from the bloodstream.

It occurs due to bleeding, significant burns or severe dehydration. It is generally referred to as hypovolemic shock.

2. The second cause may be reduced performance and heart failure

Which is also a cardiogenic shock. Which can occur with a heart rhythm disorder or a heart muscle infarction. Another subtype is obstructive shock, which arises on the basis of pericardial tamponade.

3. The third major category is vascular bed enlargement.

Simply put, when the blood vessels are excessively dilated. It's called a distribution shock. It occurs, for example, in anaphylaxis, such as anaphylactic shock, or severe sepsis.

Sepsis, septic condition, septicemia - informally called blood poisoning - which is a severe infection in which pathogens spread blood throughout the body.

The risk of shock also occurs in conditions such as:

  • diabetic coma - hyperglycemic coma, but also hypoglycemic coma
  • thyroid dysfunction
  • renal failure
  • acute liver failure
  • liver cirrhosis decompensation
  • intoxication
  • extensive injuries
  • long surgery

Classification of Shock by Cause

The shock is divided according to the cause.

Table: types of shock

Main category Shock name Cause
Insufficient fluid in the vascular bed - lack of blood Hemorrhagic due to bleeding that may occur, for example, when:
Traumatic due to injuries:
  • major bleeding, such as from an artery
  • open fractures with high blood loss
  • fractures with hidden bleeding (fractures of the thigh or pelvis)
  • organ bleeding after blunt or penetrating injuries
  • polytrauma - multiple injuries to organ systems, such as in a car accident or a fall from a height
Burn occurs in all severe burns
  • leakage of plasma - blood fluid from vessels into the extravascular space
  • generalized swelling occurs
  • reduction of circulating blood and insufficient blood supply to the tissues
  • low blood pressure
  • risk of association of infection - sepsis and septic shock
Hypovolemic with a reduced volume of fluid in the body, if sufficient replacement of lost fluids is not ensured
  • diarrhea
  • persistent vomiting
  • excessive sweating
  • excessive urination
  • peritonitis
  • ileus
  • ascites
Generally, but inaccurately, this category is referred to as hypovolemic shock. It occurs when the volume of circulating blood is reduced by more than 25-30% in 30 minutes - or with a small but long-term blood loss. When the femur is broken, the femur can receive up to 1 liter of blood - there is an enlargement of about 1 cm in circumference.
Low cardiac output per minute Decreased heart function as a pump. The amount of blood expelled from the heart decreases. There is enough blood in the blood vessels. Cardiogenic
  • myocardial infarction (heart muscle)
  • heart failure
  • acute myocarditis
  • arrhythmia - heart rhythm disorders
  • Takotsubo cardiomyopathy
    • broken heart syndrome
    • after an excessive stress response
    • loss of life partner, after separation
    • especially in postmenopausal women
    • coronary artery damage is not present in coronary angiography
    • there is no heart muscle necrosis as in myocardial infarction
  • pulmonary embolism
  • pericardial tamponade
  • tension pneumothorax
  • dissection of aortic aneurysm
  • endocarditis and valve defects
  • valve stenosis
Peripheral disorder It is also referred to as a distributive shock. There is enough blood in the blood vessels, the cause is not bleeding or heart's pumping dysfunction. Anaphylactic in case of a severe allergic reaction, i.e. anaphylaxis, for example after allergy to:
  • insect bites (bee, wasp, hornet)
  • medications
  • foods
Toxic  in chemical intoxication, but also in pancreatitis
Septic Sepsis, blood poisoning, as a complication of some infections, even with burns
Neurogenic  For brain and spinal cord injuries - especially in the neck and chest areas
Endocrine in case of impaired endocrine glands


The shock is generalized, ie a whole-body reaction. Several body systems are involved. The changes proceed gradually through the compensation phase, to the decompensation phase.

In case of treatment delay or failure up to the refraction phase. At this point, there will be a failure of the organs and entire systems and their damage. It ends in death.

Shock has general manifestations:

  • restlessness, anxiety
  • weakness, fatigue and drowsiness
  • dizziness
  • visual impairment
  • nausea, feeling sick - nausea to vomiting
  • pale skin
  • cold skin
  • excessive sweating - sticky and cold sweat
  • acceleration of heart rate, heart rate
  • the pulse is fast and difficult to feel - weak, barely palpable pulse
  • rapid breathing
  • feeling short of breath
  • disorder of consciousness at a later stage - unconsciousness
Shock - pale and sweaty skin - man's face
The manifestation is pale skin and cold sweat. Photo: Getty images

Table: Distribution of shock symptoms according to the organ system

Systemic organ Symptoms
  • abnormally rapid breathing - tachypnea
  • reduced blood flow to the lungs due to centralised circulation
  • respiratory insufficiency - "shock lung"
  • heart rate acceleration
  • heart rate accelerationheart rate acceleration
  • in the final stage intangible
  • blood pressure drops
  • until it is finally immeasurable
  • for heart muscle arrhythmia arrhythmia
  • pale
  • cold
  • increased sweating
  • cold sticky sweat
  • skin with a bluish-purple hue - cyanosis
  • turns ashen later on
  • or mottled skin
Nervous - brain - mental state
  • restlessness
  • apathy
  • malaise, weakness
  • confusion
  • fear of dying
  • sleepiness, drowsiness - somnolence
  • to consciousness disorder - unconsciousness, coma
  • there is also a risk of brain stroke
  • reduced renal blood flow
  • low output of urine - oliguria
  • non-passage of urine - anuria
  • if the kidneys are not bled for more than 90 minutes
    • kidney failure - shock kidney
  • reduction of intestinal blood flow
  • disturbance of the intestinal barrier and transfer of toxins, swelling
  • deepening of shock
  • insufficient blood supply to the liver will cause it to fail

Classification of Shock According to Clinical Severity

From this point of view, the shock is divided into mild, moderate, severe and terminal shock.

1. Mild shock

The person is weak, tired, generally depressed. The person is still conscious and has a pale, cold skin, dry mouth and is thirsty.

The skin is cold to the touch, moist and sweaty.

The activity of the heart accelerates, which we can observe as an accelerated pulse - approximately 90-100 pulses per minute. So far, the blood pressure is above 100 mmHg.

Learn more on blood pressure values in a clear table.

Bleeding may involve blood loss in the range of 1000 - 1200 ml = 20 - 25% of the volume of circulating blood.

2. Moderate shock

The mental state is deteriorating, the person is apathetic, he is not interested in the environment.

The skin is very pale - "as white as a sheet". Typically, it is cold, sticky and sweaty.

The heart rate increases to 110-120 pulses per minute - tachycardia. And at this stage, the blood pressure is also falling, with a value of less than 100 mmHg - which is called hypotension.

Learn more: Low blood pressure - hypotension.

Approximate blood loss can be estimated at 1500 - 1700 ml of blood = 30 - 35% of the circulating blood volume.

3. Severe shock

The person's mental state deteriorates and he/she is significantly weak and apathetic, moight be nauseous (feeling sick) or vomit.

The skin has a grayish tinge, associated with cyanosis - bluish-purple skin hue. We can observe it on the fingers, lips but also on the ears and the tip of the nose.

The pulse rises above 120 - 160 per minute. Blood pressure, on the other hand, drops below 80 mmHg.

In this case, blood losses can be estimated at 2,000 milliliters.

4. Terminal shock

It is the last stage of shock. The person is in immediate danger of life.

There is a disorder of consciousness - loss of consciousness, coma.

The skin is mottled. The pulse impalpable and the blood pressure at this point cannot be measured.

Irregular breathing to shallow breathing are a sign of the approaching end.

Blood loss at this stage is estimated at over 2,500 millilitres - which is 50% of the volume of circulating blood.


Early diagnosis and treatment are very important in shock. The final condition of the affected person, ie his prognosis, depends on it.

With delayed treatment, there is a risk of the shock deepening into its irreversible form and into the terminal stage, ie the death of a person.

Diagnosis includes: 

  • medical history, i.e. ask the patient whether there is pain (for example on the chest, abdomen), subjective perception of the quality of respiration, the onset of difficulties
  • clinical picture, that is, how the difficulties manifest themselves
  • physical examination - blood pressure, pulse, respiratory rate, blood oxygen saturation and others
  • blood and urine collection for laboratory examination
    • blood count, hemocoagulation, mineralogram, inflammatory markers, acid-base balance, biochemistry
  • imaging methods
    • ECG, ultrasound, X-ray, CT, MRI, sonography
    • coronary angiography in case of cardiac problems
Patient in the ambulance and rescuers
Professional diagnostics and help. Checking and monitoring vital functions. Photo: Getty images

Shock index

The Shock Index is used to indicate the level of occult shock.

The ratio between systolic pressure (sTK) and pulse frequency (P):

  1. Normal condition = 1,5 
    • which is the result of the ratio
    • 60 P per minute : 120 sTK
    • 60 : 120 = 1,5 
  2. Advanced shock = 1,0
    • 100 P per minute : 100 sTK
    • 100 : 100 = 1
  3. Severe shock = 2,0
    • 120 P per minute : 60 sTK
    • 120 : 60 = 2,0


The course of the shock and the occurrence of difficulties is conditioned by the type of shock.

Hypovolemic Shock...

It is characterized by a reduction in venous return.

It is also referred to as cold shock.

This means that the amount of blood flowing from the body back to the heart is reduced. As a result, the heart rate increases.

There is an increase on two levels, and thus an acceleration of the frequency - tachycardia, as well as an increase in the strength of contraction - inotropic state. Vascular resistance increases as well - due to vasoconstriction.

The role of this mechanism is to maintain blood flow to vital organs such as the brain and heart.

To centralise the circulation, the vessels narrow - vasoconstriction, the frequency accelerates. Significant hypotension occurs when approximately 20% of the circulating fluid volume is lost. Deceleration of the heart (bradycardia) is a sign of a late stage.

Cardiogenic Shock...

It is caused by reduced blood flow to tissues and organs. The reason is a reduction in the heart's ability to pump blood.

The minute volume of the heart decreases.

There is enough blood in the bloodstream.

Low blood pressure, decreased cardiac output, and tachycardia are also associated. Due peripheral vasoconstriction, i.e. narrowing of blood vessels in peripheral organs and tissues, the production of urine is reduced, the skin is pale, cold, sweaty, there is also muscle weakness and a change in the psyche.

Up to 75% are due to acute myocardial infarction.
On the basis of decompensated ischemic heart disease.
Another example is heart failure.

Distributive Shock...

In this form of shock, there is no vasoconstriction - narrowing of the blood vessels, but, conversely, vasodilation - which is a widening of blood vessels.

Even in this case, the amount of circulating blood is preserved.

The skin remains warm.

Warm skin, and thus increased body temperature, is caused by infection - pathogenic organisms in septic shock.

Sepsis is also associated with symptoms such as:

Sepsis is a Systemic Inflammatory Response Syndrome - SIRS to various stimuli. An example is bacterial infection, but also pancreatitis. It usually develops in the elderly and in people with comorbidities.

This type of shock is also referred to as warm shock.

Heart function is preserved throughout.

Later on, due to leaching of toxic substances, heart function deteriorates. Acidosis (shift of the pH of the internal environment towards acidic), hypoxemia (reduction of blood oxygenation), hypoxia (low tissue oxygenation) occur.

Toxic Shock Syndrome (TSS)

TSS from Staphylococcus infections was identified in the late 1970s and early 1980s when highly absorbent tampons were widely used by menstruating women.

Other causes include infection of surgical wounds, various abscesses, infection of burns, conjunctivitis.

It occurs in the presence of symptoms such as:

  • fever
  • low blood pressure
  • vomiting
  • diarrhea
  • muscle pain
  • decreased kidney function
  • changes in the psyche, apathy, confusion
  • widespread rash - exanthem
  • redness of the conjunctiva
  • coated tongue

Anaphylactic Shock

Of all the distributive forms, anaphylactic shock develops fastest, meaning within about 30 minutes of contact with the allergen.

It is the most severe form of allergy. For example, it occurs after applying medication, digesting food or an insect bite.

Signs and symptoms arise very quickly.

Anaphylactic shock occurs with:

  • severe widening of blood vessels - vasodilation
  • swelling due to increased vascular permeability
  • skin manifestations such as hives - urticaria, redness
  • pallor and cyanosis
  • low blood pressure due to reduced cardiac output
  • common cold
  • nausea or vomiting
  • abdominal pain - cramps
  • constriction of the muscles in the walls of the bronchiole - bronchospasms
  • eventually circulatory failure, pulmonary edema
Administration of EpiPen for an allergy sufferer
An allergy sufferer should carry an Epipen at all times - it is important to administer it quickly and thereby prevent the development of shock. Photo: Getty images

Neurogenic Shock

Neurogenic shock occurs through the presence of the triad of symptoms, namely hypotension (low blood pressure), bradycardia (decrease in heart rate) and hypothermia (decrease in body temperature). Vasodilation, i.e. the widening of blood vessels, is also present.

The cause may be vagotonia, ie irritation of the vagus nerve - a wandering nerve, deep general anesthesia, exaggerated emotions - fear, brain damage or bloodless spinal cord.

A spinal shock is different in that it occurs when the spinal cord is injured.

In spinal shock, sympathetic stimulation is increased, which is manifested by a sudden high blood pressure, with a high or low heart rate. High blood pressure is replaced by a drop in blood pressure, even in the long term.

How it is treated: Shock - State of shock

Shock treatment: By type + shock first aid

Show more

Shock, Pathology of Different Types, Animation

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Interesting resources

  • International Trauma Life Support for Emergency Care Providers (8 ed.). Pearson Education Limited. 2018. pp. 172–73. ISBN 978-1292-17084-8.
  • ATLS – Advanced Trauma Life Support – Student Course Manual (10 ed.). American College of Surgeons. 2018. pp. 43–52, 135. ISBN 978-78-0-9968267.
  • Tabas, Jeffrey; Reynolds, Teri (2010). High Risk Emergencies, An Issue of Emergency Medicine Clinics (E-book). Elsevier Health Sciences. p. 58. ISBN 978-1455700257.
  • Smith, N; Lopez, RA; Silberman, M (January 2019). "Distributive Shock". PMID 29261964.
  • Olaussen A, Blackburn T, Mitra B, Fitzgerald M (June 2014). "Review article: shock index for prediction of critical bleeding post-trauma: a systematic review". Emergency Medicine Australasia26 (3): 223–28. doi:10.1111/1742-6723.12232. PMID 24712642. S2CID 19881753.
  • Guyton, Arthur; Hall, John (2006). "Chapter 24: Circulatory Shock and Physiology of Its Treatment". In Gruliow, Rebecca (ed.). Textbook of Medical Physiology (11th ed.). Philadelphia, Pennsylvania: Elsevier Inc. pp. 278–88. ISBN 978-0-7216-0240-0.
  • Tintinalli, Judith E. (2010). Emergency Medicine: A Comprehensive Study Guide. New York: McGraw-Hill Companies. pp. 165–72. ISBN 978-0-07-148480-0.
  • Tintinalli, Judith E. (2010). Emergency Medicine: A Comprehensive Study Guide. New York: McGraw-Hill Companies. pp. 174–75. ISBN 978-0-07-148480-0.
  • Assessing dehydration and shockNCBI Bookshelf. National Collaborating Centre for Women's and Children's Health (UK). April 2009. Retrieved 2019-05-09.
  • Silverman, Adam (Oct 2005). "Shock: A Common Pathway For Life-Threatening Pediatric Illnesses And Injuries". Pediatric Emergency Medicine Practice2 (10).