When the blood leaves the cells, it carried their waste products back into tiny veins, which pour into larger ones and finally into the largest veins which feed directly into the heart.

Now the blood has almost made a round trip - but there is one more stop before circulating once again.  The heart pumps blood to the lungs and back to the heart.  In the lungs, the blood loses the waste gases (mostly carbon dioxide) it has picked up in the cells, and each red blood cell picks up a new load of oxygen.  Then it returns to the heart and the heart pumps it again through the arteries to the cells.

The blood also goes through an amazing effective "filtering system" called the kidneys.  The kidneys remove all the liquid wastes which couldn't be taken out by the lungs.  They also remove the extra salts and minerals the body doesn't need.  These wastes as urine pass down tubes called ureters into the bladder.

The most important point of this whole process is the provision of oxygen and food to the cells.  If this is interrupted for only a few minutes, cells start to die.  If the cells that die are in the vital organs-especially the brain, heart, or kidneys - the whole body will also quickly die. When organs are not getting enough oxygen to work properly, the signs of shock start to show.

But what causes Shock?

In order for the blood to get oxygen to the cells, the blood has to be under some pressure.   This pressure is provided by the pump - the heart - and maintained by the veins and arteries, which are able to get slightly larger or smaller to control the pressure.

Several things might cause this pressure to drop.  If there is a "leak" in the system, from a bad cut, blood flows out and the pressure drops.  The body tried to deal with this automatically. 

How can we tell it is doing this?

ÞBecause circulation to t he skin is not as important as circulation to the vital organs, the body cuts down the size of blood vessels at the surface. so the skin gets paler and cooler.

ÞBecause there is not enough blood to fill t he system, your heart automatically beats faster to get more oxygen to all the cells, so your pulse rate goes up.

ÞBecause your cells are not getting enough oxygen,  your breathing rate automatically speeds up.

Þ Because the body is trying to save all the fluid in it, it stops producing saliva and you feel thirsty.

ÞBecause circulation to the stomach and intestines is less important than that to the vital organs, the body cuts down blood flow to the gastrointentestinal tract, so absorption of food and water stops and you may feel nauseated.

ÞBecause the cells of the body need more oxygen, you feel "hungry" for more air.

Because the brain is not getting enough oxygen, you get confused and anxious.

Now that you know what happens in the body, you can see what causes the signs and symptoms of shock.  Again these are:

* pale, cool, clammy skin
* rapid pulse rate
* rapid breathing
* thirst
* nausea and sometimes vomiting
* air hunger
* anxiety or nervousness
* confusion
* decreased amounts of urine

 Other factors besides blood loss can cause shock.  Serious burns almost always do.  Clear or pale yellow fluid, which comes directly from the blood, oozes from the burn in large amounts and also goes into the tissues around the burn as swelling. Because this fluid comes directly from the blood, the amount left in the system is less, and shock occurs.

Several types of illnesses can bring on shock by causing the large blood vessels in the trunk to loosen and expand.  The vessels become bigger and can hold  more, but the amount of blood in them remains the same, so the blood pressure drops.  Sometimes, a severe emotional shock can cause this to happen.  ("Fainting" is not the same as shock but is caused by a shortage of blood to the brain.)

A violent allergic reaction to a drug or insect sting can cause shock.  So can injury to the spinal cord.

Once shock starts, it may be difficult to reverse.  If not stopped or reversed, the casualty will die.  So you must always.

 Field prevention and treatment of shock are simple.  You must:

* ensure a good airway 
* control the bleeding
* lie the casualty down, feet raised 8 to 12 inches (Do not tilt the
  entire body if there is difficulty breathing)
* keep the casualty comfortable warm
* avoid rough handling
* reduce pain as much as possible (for example, by splinting
  fractures, etc.)
* reassure the casualty

Since the problem is basically one of oxygen shortage to the cells, you must be sure that the casualty is breathing with maximum efficiency.  Since low blood pressure is a factor, you must be sure no more blood is lost. Maintain pressure and bandage and wounds. Raising the legs increases the return of blood to the heart.  Keeping the casualty warm is especially critical, because the skin, with a decreased blood supply, is more vulnerable to injury from cold.

Rough handling increases shock.  So does pain.  And reassurance has been shown to have a positive effect on blood pressure and certainly on the casualty's survival attitude.

The first aider should not be fooled into thinking there is no shock problem if shock does not appear serious immediately after blood loss.  The body compensates  in so many ways for the initial blood loss t hat pressure may be maintained for a time.  With continuing loss, however, shock may appear rapidly.
Next:  Breathing Problems