• Tim

Clinical Shock

Updated: Apr 26, 2021

The word 'shock' is common in our language, but not many people understand what clinical shock is, or why it's so important. Read on to find out what causes shock, and what to do if you recognise it in someone.


Clinical shock has many definitions, but essentially, it occurs when vital organs are unable to get sufficient oxygen and nutrients from the blood, usually due to a decreasing blood pressure. This also leads to a build up of waste products, further complicating matters.

Shock is not a condition in itself, rather it's a syndrome that occurs as a result of other problems.

Interestingly, being psychologically 'shocked' by something can also have physiological symptoms, but it's not what we mean by clinical shock.


Shock can have a number of different causes...


Due to a reduction in blood volume, such as significant external or internal bleeding, burns or dehydration.


Due to a problem with the heart, such as a heart attack or arrhythmia, where the heart is not pumping properly.


Due to a problem with the location of the blood, where the blood vessels lose their tone and become larger due to an anaphylactic reaction.


Due to a problem with the return of blood to the heart, usually due to a blood clot in the lungs or pressure on the main blood vessels.


Due to a systemic infection that lowers blood pressure.


Due to a problem with the brain or nerves that control blood vessels and the heart, such as when someone has a brain or spinal injury.


The symptoms of shock are fairly common across the different types as it is the same system that responds to any threat to the body.

This is our 'fight or flight' response, and is largely due to adrenaline being released into the blood.

Initially, this will cause an increase in heart rate and an associated increase in breathing rate which may be observable.

It will also lead to the body shutting down non-critical systems. This includes the digestive system, so people may feel nauseous, or even be sick. They could also be incontinent.

It may also lead to shutting down of the blood flow to the skin, making someone appear pale and cold to touch, just like when they are in a cold environment. This is achieved by tightening the peripheral blood vessels.

However, in allergic, septic and neurogenic shock, the person has lost control of this mechanism, so the signs will not be present, and the person may be warm to touch.

As oxygen is not being adequately delivered to the peripheries, patients may also show signs of cyanosis - a bluish discolouration of the skin, usually seen first in the lips and extremities.

The adrenaline response will also initiate sweating. If the skin has been shut down, the sweat won't evaporate, will sit on the surface of the skin and make the person 'clammy'.

These compensatory mechanisms are all aimed at maintaining blood pressure in order to get blood to the vital organs. However, if they are not enough to achieve sufficient pressure, the person may lose consciousness. This is known as decompensation. They may become confused or not be able to speak clearly, they may get anxious, irritable or aggressive and they may even have a seizure.

It's worth noting that children and young people compensate very well, making it difficult to recognise the early stages of shock. This also means that when their compensatory mechanisms run out, they decompensate and collapse rapidly. This is a life-threatening emergency. For this reason, children who could be experiencing shock should be treated extremely cautiously.


The treatment of shock by a first aider has two parts. After calling 999...

Stop or reversing the cause (if possible) and then treat the shock

If the person is unconscious, you'll need to manage their airway. Read this blog post for more information.

Obviously, stopping or reversing the cause of the shock should be a priority. This could involve arresting any significant bleeding or administering an adrenaline auto-injector for instance.

Then, it's about treating the shock. As the problem is due to the inability to get blood to the brain, lying the person down means that the heart is not having to fight gravity.

In reality, the person will either have automatically put themselves in this position, or will have collapsed anyway.

As long as the person isn't experiencing shock as a result of trauma, the person's legs can also be raised. This allows blood to drain out of them, further increasing blood pressure.

In trauma though, raising the legs could cause problems with leg, pelvic or spinal injuries, as well as blood clots associated with internal bleeding. Evidence shows that raising the legs in traumatic shock does not have an impact on patient outcomes.


Shock is a set of signs and symptoms caused by another problem that affects someone's blood pressure.

They may be breathing faster than normal, have nausea or vomiting and be sweaty. They may also have cold, pale skin, depending on the cause of the shock.

Call 999 and if necessary, manage their airway. Treat the cause of the shock and lie them down with their legs raised (except in trauma).


If you'd like to know more about shock and what to do if someone is experiencing a life-threatening problem, why not book on to one of our face-to-face, blended learning or online first aid courses.