What is shock?

Shock occurs if you don't have enough blood circulating around your body to provide oxygen to your organs.

Shock is a medical emergency. If left untreated, it can be fatal.

The most common cause of shock is major bleeding; for example, if someone has suffered an injury and lost a lot of blood. But it can also happen in people with serious infections, allergic reactions or heart conditions.

At first your body will try to increase your blood pressure by narrowing the blood vessels in your hands and feet (known as vasoconstriction). This increases blood flow to your heart, brain and other vital organs. The body also releases adrenaline, which can cause your blood pressure to drop further, which can be fatal.

If your brain, heart and other organs don't receive enough blood flow for an extended time, they will not have enough oxygen to function, and may stop working.

What is non-medical (emotional) shock?

Non-medical 'shock' refers to when a person experiences a sudden fright or emotional event. It leads to a sudden but short-term release of adrenaline. In a healthy person, this will usually pass without medical treatment.

You can help someone experiencing emotional shock by being calm and reassuring and encouraging them to use anxiety management techniques, such as mindfulness, to manage their symptoms.

What are the symptoms of shock?

Symptoms of mild shock include:

• dizziness
• nausea
• anxiety or restlessness
• pale face, fingernails and lips

As shock progresses, it can cause:

• thirst
• a weak, rapid pulse
• fast, shallow breathing
• blue face, fingernails and lips
• drowsiness and confusion
• collapse

What causes shock?

There are many conditions that can affect blood flow around the body and lead to a dangerous drop in blood pressure.

Conditions such as blood loss and dehydration cause shock by reducing the amount of blood available to circulate around the body.

Conditions that affect the heart's ability to pump blood around the body effectively can also cause shock. These include:

• myocardial infarction — heart attack
• cardiomyopathy — disease that affects your heart muscle
• arrhythmia — irregular heartbeat
• pulmonary embolism — blood clot in your lungs

Some conditions cause blood vessels to dilate (relax) too much, causing a drop in blood pressure and a reduction in blood flow around the body. These include:

• some neurological conditions, such as spinal cord injury
• sepsis — widespread infection
• anaphylaxis — severe allergic reaction

When should I call an ambulance?

You should call triple zero (000) and ask for an ambulance if you or someone else:

• is having trouble breathing or is turning blue
• loses consciousness
• has suffered a severe injury
• has severe bleeding that can't be controlled by applying pressure
• has central or crushing chest pain
• is having an anaphylactic reaction
• sudden inability to move or speak, or sudden facial drooping

Follow the first-aid advice below and any instructions given by the triple zero (000) operator.

How is shock treated?

First-aid for shock

If someone nearby is experiencing shock, acting quickly can save their life. Follow these steps:

1. Ensure your own safety and that of anyone else at the scene.
2. Help the person lie down — do not raise their legs. Loosen any tight clothing. Place the person in the recovery position if they have difficulty breathing, are unconscious or might vomit.
3. Control any obvious bleeding.
4. Call triple zero (000) and ask for an ambulance.
5. Treat the underlying cause of the person's condition, if you know what it is. For example, if a person is experiencing shock due to anaphylaxis, administer an adrenaline autoinjector and follow their ASCIA allergy action plan if they have one.
6. Keep the patient warm with a blanket or other covering.
7. Reassure the person and monitor their condition for any change.
8. If the person becomes unconscious and stops breathing normally, start CPR.

Learn more about first aid.

Medical treatment for shock

Treatment for shock will depend on the severity and the cause.

Initial treatment usually involves stabilising the person's blood pressure with intravenous (IV) fluids or medicines. Many people with shock need treatment in hospital, sometimes in an intensive care unit.

If blood loss has led to shock, treatment might involve a blood transfusion, and managing the cause of the bleeding (such as a wound or injury or a medical condition).

If a medical condition such as heart attack, pulmonary embolism, anaphylaxis or sepsis has caused shock, treatment will also involve managing these conditions.

What are the complications of shock?

Shock means that the brain, heart and other vital organs will not get enough oxygen. Untreated, this can lead to organ damage, which may be irreversible and may be fatal.

The chances of someone surviving shock and how well they recover will depend on:

• their age and general health
• what caused the shock
• the severity of the shock
• how soon they receive treatment

Resources and support

• The Australian and New Zealand Committee on Resuscitation (ANZCOR) publishes guidelines on the management of shock and other aspects of first aid.
• St John's Ambulance Australia has many fact sheets about giving first aid for shock as well as many other medical conditions.

Do you prefer to read in languages other than English?

• St John's Ambulance Australia has fact sheets about first aid in many community languages.