Doctor's Notes on Shock
Shock is defined as abnormal metabolism (usually not enough oxygen) at the cellular level; shock is considered the in stage of all diseases in the symptoms will vary with the underlying causes. This abnormal metabolism causes organs to begin to lose their ability to compensate. In general, when shock occurs, breathing rate gets faster and the heartbeats faster also. As the organs begin to decompensate, blood pressure frequently begins to drop. As body cells fail to get enough oxygen other signs and symptoms may develop such as confusion, chest pain, diarrhea, acute renal failure and the skin becomes clammy and pale. Then loss of consciousness, coma and/or death occurs if the underlying problem is not treated.
The causes of shock are many; however, the most basic underlying problem is that cells in one or more organs are deprived of oxygen so they cannot make the organ function normally. Some examples of underlying problems that may decrease oxygen delivery are as follows: large blood loss from trauma, GI bleeding or dehydration, the amount of oxygen in the air is decreased (high altitudes, carbon monoxide poisoning), lung injury (pneumonia, congestive heart failure, pulmonary edema, lung trauma), heart problems such as heart attack arrhythmia, pericarditis, inflammation of heart muscle. Any underlying cause of bleeding problems can cause shock including cancers, leukemia, bleeding from the uterus or during childbirth.
Shock is defined as abnormal metabolism at the cellular level. Since it is not easy to directly measure cellular problems, the symptoms of shock are indirect measurements of cellular function. Shock is the end stage of all diseases, and symptoms will often be dependent on the underlying cause.
As the patient goes through the various stages of shock, vital signs change. In the early stages, the body tries to compensate by moving fluids around from within cells to the blood stream with an attempt to maintain blood pressure in a normal range. However, there may be a slight rise in the heart rate (tachycardia = tachy or fast + cardia or heart). For example, donating blood. A unit of blood (or about 10% of the blood volume) is removed, yet the body compensates well, except for a little lightheadedness, which is often resolved by drinking fluids. Another example is exercising and forgetting to drink enough fluids and feeling a little tired at the end of the day.
As the body loses the ability to compensate, the breathing rate gets faster and the tachycardia increases as the body tries to pack as much oxygen onto the remaining red blood cells as possible and deliver them to the cells. Unfortunately, blood pressure starts to drop (hypotension=hypo or low + tension= pressure) as compensation mechanisms fail.
Cells don't receive enough oxygen and the organs that they comprise begin to fail. All organs may be affected.
- As the brain is affected, the patient may become confused or lose consciousness (coma).
- There may be chest pain as the heart itself doesn't get an adequate oxygen supply.
- Diarrhea may occur as the large intestine becomes irritated due to hypotension.
- Kidneys may fail and the body may stop producing urine.
- The skin becomes clammy and pale.
When things go wrong
If cells are deprived of oxygen, instead of using aerobic (with oxygen) metabolism to function, the cells use the anaerobic (without oxygen) pathway to produce energy. Unfortunately, lactic acid is formed as a by-product of anaerobic metabolism. This acid changes the acid-base balance in the blood, making it more acidic, and can lead to a situation in which cells begin to leak toxic chemicals into the bloodstream, causing blood vessel walls to become damaged. The anaerobic process ultimately leads to the death of the cell. If enough cells die, organs start to fail, and the body starts to fail and, eventually, death occurs.
Think of the cardiovascular system of the body as similar to the oil pump in your car. For efficient functioning, the electrical pump needs to work to pump the oil, there needs to be enough oil, and the oil lines need to be intact. If any of these components fail, oil pressure falls and the engine may be damaged. In the body, if the heart, blood vessels, or bloodstream (circulation) fail, then eventually, death occurs.
Where things go wrong
The oxygen delivery system to the body's cells can fail in a variety of ways.
- The amount of oxygen in the air that is inhaled can be decreased.
- Examples include breathing at high altitude or carbon monoxide poisoning.
The lung may be injured and not be able to transfer oxygen to the blood stream. Examples of causes include:
- pneumonia (an infection of the lung),
- congestive heart failure (the lung fills with fluid or pulmonary edema), or
- trauma with collapse or bruising of the lung, or
- pulmonary embolism.
The heart may not be able to adequately pump the blood to the tissues of the body. Examples of these causes examples include:
- Heart attack in which muscle tissue is lost and the heart cannot beat as strong and pump blood throughout the body.
- A rhythm disturbance of the heart occurs when the heart can't beat in a coordinated way.
- Inflammation of the sac around the heart (pericarditis) or inflammation of the heart muscle due to infections or other causes, in which the effective beating capabilities of the heart are lost.
There may not be enough red blood cells in the blood. If there aren't enough red blood cells (anemia), then not enough oxygen can be delivered to the tissues with each heart beat. Examples of causes may include:
- acute or chronic bleeding,
- inability of the bone marrow to make red blood cells, or
- the increased destruction of red blood cells by the body (an example, sickle cell disease).
There may not be enough other fluids in the blood vessels. The blood stream contains the blood cells (red, white, and platelets), plasma (which is more than 90% water), and many important proteins and chemicals. Loss of body water or dehydration can cause shock.
The blood vessels may not be able to maintain enough pressure within their walls to allow blood to be pumped to the rest of the body. Normally, blood vessel walls have tension on them to allow blood to be pumped against gravity to areas above the level of the heart. This tension is under the control of the unconscious central nervous system, balanced between the action of two chemicals, adrenaline (epinephrine) and acetylcholine. If the adrenaline system fails, then the blood vessel walls dilate and blood pools in the parts of the body closest to the ground (lower extremities), and may have a difficult time returning to heart to be pumped around the body.
Since one of the steps in the cascade of events causing shock is damage to blood vessel walls, this loss of integrity can cause blood vessels to leak fluid, leading to dehydration which initiates a vicious circle of worsening shock.
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Trauma and First Aid : Training and Supplies QuizQuestion
Emotional trauma is best described as a psychological response to a deeply distressing or life-threatening experience.See Answer
Kasper, D.L., et al., eds. Harrison's Principles of Internal Medicine, 19th Ed. United States: McGraw-Hill Education, 2015.