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A basic overview of shock for EMS

A review of shock stages, signs and symptoms and treatments for the EMT or paramedic student


Shock is caused by four major categories of shock causes are encountered in EMS by EMTs and paramedics: cardiogenic, hypovolemic, septic and anaphylactic

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Shock is a medical emergency that occurs when the organs and tissues of the body are not receiving an adequate flow of blood. Shock is also described as inadequate perfusion. The lack of perfusion deprives the organs and tissues of oxygen, carried in the blood, and causes the buildup of waste products. Shock can result in serious tissue damage, organ failure or even the patient’s death.

Description of shock

There are three stages of shock:

  • Stage I - also called compensated, or nonprogressive
  • Stage II - also called decompensated or progressive
  • Stage III - also called irreversible

In Stage I shock low blood flow (perfusion) is first detected, a number of systems are activated in order to maintain/restore perfusion. The result of that activation is that the heart beats faster (tachycardia), breathing is faster (tachypnea) the blood vessels throughout the body become smaller in diameter (vasoconstriction), and the kidneys work to retain fluid in the circulatory system. The patient is likely to be awake on the AVPU scale, but may have altered mental status like confusion, irritability or lethargy.

Because the body is attempting to main critical systems, such as the brain, heart, liver and kidneys, you may notice changes in the patient’s skin condition. Pale skin, cool skin, and blue-tinged lips are a result of inadequate perfusion of the skin.

These compensatory mechanisms serve to maximize blood flow to the most important organs and systems in the body. Since the patient is compensating, the patient’s blood pressure is likely within normal limits. The patient in this stage of shock has primarily vital sign changes and aggressive treatment may slow progression.

In Stage II of shock, these compensation methods begin to fail. The systems of the body are unable to improve perfusion any longer, and the patient’s symptoms reflect that fact. Oxygen deprivation in the brain causes the patient to deteriorate to V, P, U on the AVPU scale. Heart rate, breathing rate are still above normal and blood pressure may be close to normal or below normal.

In Stage III of shock, the length of time that poor perfusion has existed begins to take a permanent toll on the body’s organs and tissues. The heart’s functioning continues to spiral downward, and the kidneys usually shut down completely. Heart rate and respiratory rate are well above normal, until crashing to low rates incompatible with life. The patient’s blood pressure is also precipitously low. Cells in organs and tissues throughout the body are injured and dying. The endpoint of Stage III shock is patient death.

Shock causes

Shock is caused by four major categories of shock causes are encountered in EMS by EMTs and paramedics:

  1. Cardiogenic shock: meaning problems associated with the heart’s functioning
  2. Hypovolemic shock: meaning that the total volume of blood available to circulate is low
  3. Septic shock: caused by overwhelming infection, usually by bacteria
  4. Anaphylactic shock - caused by an overwhelming allergic reaction, usually caused by a systemic response to a bee sting, food allergen, or other types of allergens.

Cardiogenic shock can be caused by any disease, or event, which prevents the heart muscle from pumping strongly and consistently enough to circulate the blood normally. Heart attack (myocardial infarction), conditions which cause inflammation of the heart muscle (myocarditis), disturbances of the electrical rhythm of the heart, any kind of mass or fluid accumulation and/or blood clot which interferes with flow out of the heart can all significantly affect the heart’s ability to adequately pump a normal quantity of blood.

Hypovolemic shock occurs when the total volume of blood in the body falls well below normal. This can occur when there is excess fluid loss, as in dehydration due to severe vomiting or diarrhea, diseases which cause excess urination (diabetes insipidus, diabetes mellitus, and kidney failure), extensive burns, blockage in the intestine, inflammation of the pancreas (pancreatitis), or severe bleeding of any kind.

Septic shock can occur when an untreated or inadequately treated infection (usually bacterial) is allowed to progress. Bacteria often produce poisonous chemicals (toxins) which can cause injury throughout the body. When large quantities of these bacteria, and their toxins, begin circulating in the bloodstream, every organ and tissue in the body is at risk of their damaging effects. The most damaging consequences of these bacteria and toxins include poor functioning of the heart muscle; widening of the diameter of the blood vessels; a drop in blood pressure; activation of the blood clotting system, causing blood clots, followed by a risk of uncontrollable bleeding; damage to the lungs, causing acute respiratory distress syndrome; liver failure; kidney failure; and coma.

Shock diagnosis

The diagnosis of shock is based on identifying a mechanism for shock, the patient’s symptoms, and the patient’s vital signs. A significant drop in blood pressure is usually a late finding, Stage III, and don’t delay care waiting for blood pressure to drop below normal. Extremely low urine output, measured at the hospital or skilled nursing facility, is a possible indicator of shock as the patient’s body is working to maintain adequate fluid volume. Blood test can diagnosis infection causing sepsis.

Prehospital Treatment of shock

The most important goals in the prehospital treatment of shock include:

  • Finding and fixing the cause of the patient’s shock with the tools and treatments available to your level of certification and scope of practice. If the patient has no pulse, start CPR. If you see severe extremity bleeding, apply a tourniquet. If the patient has anaphylaxis after a bee sting, administer epinephrine.
  • Determining the patient’s shock stage - Stage I, Stage II, and Stage III).
  • Treat the effects of shock with oxygen, IV fluid administration and medications to maintain critical body systems.

During transport, keep the patient warm, continue to monitor vital signs, and continue treatments.

Shock prognosis

The prognosis of an individual patient in shock depends on the stage of shock when treatment was begun, the underlying condition causing shock, and the general medical state of the patient.

Read next: Compensated vs. decompensated shock: what you need to know

This article, originally published July 31, 2008, was adapted from a Health A to Z article. The article has been updated.

EMS 101 articles are intended to educate a non-emergency medical services audience about the emergency medical services profession. These articles are written by EMS1 staff members and EMS1 contributors, and cover a wide range of topics from EMS protocols all paramedics & EMTs should follow to an overview of the necessary requirements for becoming a paramedic.