Circulatory Shock: Definition, Causes, Symptoms and Treatments

It is the failure of the circulatory system to supply enough blood to the peripheral tissues.

This prevents basic metabolic oxygen and nutrient requirements and incomplete removal of metabolic wastes from affected tissues from being met.

Causes and symptoms

Shock is usually caused by bleeding or overwhelming infection and is characterized in most cases by:

  • Weak and rapid pulse.
  • Low blood pressure.
  • Cold and sweaty skin

Depending on the cause, however, some or all of these symptoms may be missing in individual cases.

Shock can be the result of a variety of physiological mechanisms, including:

  • Sudden reductions in total blood volume through acute blood loss, as in severe bleeding.
  • Sudden reductions in cardiac output, as in myocardial infarction (heart attack); and generalized dilation of blood vessels, as in some forms of infection.

Whatever the central physiological mechanism, the effect of the shock is to reduce blood flow through the small vessels or capillaries, where oxygen and nutrients pass into the tissues and waste is collected for elimination.

Shock is generally classified according to its presumed cause, although in many cases the true cause of peripheral circulatory failure may not be apparent.

The most common cause of shock is massive blood loss, either from trauma or from surgery. In the latter case, blood loss can be anticipated and shock prevented by providing blood transfusions during and after the operation.

Acute blood loss reduces the amount of venous blood returning to the heart, which in turn reduces cardiac output and causes a drop in blood pressure.

Pressure receptors, or baroreceptors, in the walls of the aorta and carotid arteries trigger physiological reflexes to protect the central circulation, increase heart rate to increase cardiac output, and constrict small blood vessels to direct blood flow to the essential organs.

If blood loss continues, even these mechanisms fail, producing a sharp drop in blood pressure and overt manifestations of shock.

Loss of blood plasma in burns or dehydration can also reduce blood volume enough to induce shock.

The output of blood from the heart can also be reduced sufficiently for a product shock without blood loss.

In coronary thrombosis, the blood supply to the heart muscle through the coronary artery is interrupted by a blood clot or vascular constriction; damaged muscle may lack the strength to force a normal volume out of the heart with each stroke.

Again, decreased production activates baroreceptors in the arteries to restrict peripheral circulation.

Blood clots that block blood flow to the lungs (pulmonary embolism) or increase the fluid that surrounds and cushions the heart (cardiac tamponade) can also affect the pumping of the heart enough to cause shock.

The most common cause of shock from dilated blood vessels is massive. Bacterial infection, which can be further exacerbated by reductions in total blood volume caused by fluid losses secondary to infection.

In general, the toxins produced by the bacteria are the cause of the dilation. Foreign substances in the bloodstream can also produce a form of shock, called anaphylactic shock, through allergic reactions that dilate the blood vessels.

Another possible cause of vascular dilation shock is drugs; many anesthetic medications create a controlled shock that must be carefully controlled by adjusting the dose, and overdoses of several of these medications, including barbiturates and narcotics, produce symptoms of shock

The main problem in treating shock is recognizing the cause of the physiological problem, since several possible causes can coexist in a single patient, especially after an accident.

Failure to distinguish between shock caused by inadequate cardiac output and that caused by fluid losses that reduce blood volume can lead to a therapeutic dilemma, as treatments that are effective for one type of shock will aggravate the other. .

Intravenous fluids are the usual treatment for shock caused by blood loss, but adding extra fluid to the circulation can overload a damaged heart that is already low output, deepening the shock.

When the cause of the shock is unclear, doctors may do a test with intravenous fluids; If central venous pressure rises, indicating decreased cardiac capacity, fluids stop before the heart can be compromised.

Shock secondary to bacterial infection can be treated with a combination of fluid replacement and appropriate antibiotics, while anaphylactic shock can be treated with epinephrine and antihistamines, which counteract the acute allergic response.


Treatment aims to restore blood flow and protect organs from damage. The options include:

  • Medicines.
  • Cardiac procedures and surgery.
  • Medical devices.

Some people may need a heart transplant or a permanently implanted device to help maintain blood flow after circulatory shock.

If the circulatory shock was caused by lung problems or medication side effects, your doctor will treat those problems. If not treated quickly, circultural shock can lead to life-threatening organ failure or brain damage.

Remember that this article is only for the purpose of informing you. If you have any symptoms, go to the nearest medical center.