Shock

When some says “I am shocked” or “I was in a shock”, one means being upset or surprised. However, the word "shock" in medical terminology means a life-threatening circulatory failure. Shock is a situation when our cardiovascular system is unable to deliver enough oxygen and nutrients to the tissues and at the same time the waste products of our metabolism out of the tissues.m Since the shock develops due to the collapse of our cardiovascular system*, it is clear that it is a life-threatening state. Once the shock condition develops, the situation is fatal, unless rapid and aggressive treatment is introduced.

 

* Cardiovascular system is, simply said, a closed system of tubes (blood vessels) containing fluid (blood), which is driven by a pump (the heart). The description of every type of shock can be well described according to this simple scheme.

Causes

The medical textbooks differentiate the shock conditions according to the cause into hypovolemic, cardiogenic, obstructive and distributive. It is quite a logical and understandable division.

Hypovolemic shock

This circulatory shock occurs due to the lack of body fluids. It is simple; the lack of fluids in the body also means the lack of fluids in the bloodstream and this leads to the failure of cardiovascular system. The heart pumps normally, but when there is no fluid in the “pipes”, it has no effect. The most common situations leading to hypovolemic shock are dehydration, fluid loss in extensive burns and heavy bleeding (external or internal). When the situation is caused by heavy bleeding, we speak about the “hemorrhagic shock”.

Cardiogenic shock

This type of shock is caused by the failure of the “pump”, i.e. the heart failure. The “tubes” are healthy and normal amount of fluid is present, but when the heart stops working, the fluid can not flow. There are numerous causes of the heart failure (heart attack, arrhythmias, heart valve diseases, myocarditis, cardiomyopathy, etc.) and you can find them in the related article.

Obstructive shock

In this case, the shock is caused by external oppression or internal blockage of a substantial part of the bloodstream. If the tubes become blocked, the flow of the fluid is disrupted.  The most common cause of this type of shock is extensive and sudden pulmonary embolism when the pulmonary arteries are blocked by blood clots. The obstructive shock also includes cardiac tamponade, when the heart is compressed by fluid located in the pericardial space.

Distributive shock

This is probably the most interesting and complex type of the shock. It is related to a massive leakage of the blood fluid from the blood vessels into the surrounding tissues. The total amount of the body fluid does not change, but it is missing in the blood vessels. The consequences are very similar to hypovolemic shock. And why does the fluid come out of the blood vessels? The permeability of blood vessels is normally strictly regulated by multiple internal mechanisms. However, severe inflammatory processes such as the strong allergic reaction (anaphylactic shock) or sepsis (septic shock) produce a large amount of inflammatory substances that cause increased vascular permeability. This is good in small local inflammation as the increased permeability improves the local immune reaction and penetration of white blood cells directly into the area. However, such whole-body reaction may easily lead to a sudden cardiovascular failure.

Symptoms

Shock states are more or less similar with symptoms resulting from insufficient blood flow to tissues. The heart tries to pump faster and increases the pulse rate. This, however, is insufficient and the deterioration of circulatory system is reflected as a decrease of the blood pressure. The pulse is fast, but worse palpable. However, some cases of the cardiogenic shock occurring due to arrhythmias may have present bradycardia (slow heart rate below 60 bpm).

 

The organism tries to ensure the blood supply of crucial organs at all cost. The skin blood vessels narrow and the blood is moved to more necessary tissues and organs. Therefore, the skin is pale and peripheral parts of the body turn cold. Deterioration of blood supply of the kidneys decreases the production of urine and its output (the affected person produces only a small amount of urine or stop urinating at all). In the end, the disruption of blood flow affects the brain and causes, confusion, unconsciousness and death.

 

The damage of multiple organs during a shock is known as the MODS (multiple organ dysfunction syndrome) and the final failure is referred to as MOF (multiple organ failure).

Treatment

The shock must be always regarded as a very serious condition and the patients must be hospitalized in intensive care unit. The therapy should focus on treatment of the causative factor and on maintaining the circulation at all cost. In case of hypovolemia, the fluid is administered intravenously in infusions; many liters per day may be needed. When the patient is unable to maintain adequate blood pressure, we use vasoactive drugs such as the epinephrine or norepinephrine.

 

Virtually every type of shock needs ensuring a sufficient supply of oxygen to the tissues. Sometimes, oxygen mask is sufficient, but when there is a respiratory failure, the patient should be intubated and connected to artificial lung ventilation.

 

In hypovolemic shock, we try to prevent further loss of the body fluids. In cardiogenic shock, we treat the heart failure. Obstructive shock due to pulmonary embolism can be treated by drugs reducing the blood clotting or drugs that directly dissolve the thrombi. Cardiac tamponade must be urgently solved by puncturing the pericardial space and draining the fluid. Distributive shock caused by sepsis is treated by antibiotics and anaphylactic shock by anti-allergic medications (typically by intravenous corticosteroids).

Summary

  • Hypovolemic shock – little fluid in the body, simple dehydration, burns, bleeding
  • Cardiogenic shock – heart failure, coronary heart disease, valvular disorders, arrhythmias
  • Obstructive shock – obstruction or compression of blood vessels – embolism, tamponade
  • Distributive shock – the movement of blood from the blood vessels into surrounding tissues, includes anaphylactic shock and septic shock
  • Treatment of shock – fluids intravenously, cardiac support, sufficient oxygen intake, removing the causes of shock