SHOCK

The person who is pale ,cold and clammy after an accident is almost certainly likely to be suffering from shock. Speedy treatment by blood transfusion can often be a life saver to the gravely ill shock victim

There is a big difference between the way that most people use the word’ shock and the way that doctors use it. In the ordinary way we talk about a sudden event giving rise to an unpleasant surprise - a shock in fact. On the other hand, to the doctor shock is a medical condition in which the collapse of the circulation for the one reason or another is a central feature. Sometimes, the different uses of the word cause confusion.

PSYCHOLOGICAL SHOCKS

It would be wrong to ignore totally the effects of sudden unpleasant psychological shocks: they can often cause considerable distress and can even precipitate serious psychological illness. But this is only likely in people already at risk of mental illness.

Sudden psychological shocks can cause collapse on their own - people may faint and it is not unknown for people to faint when they are given bad news. Also, an unpleasant or horrifying experience can lead to the development of serious symptoms of anxiety; this is particularly likely to happen to the victims of violent crime.

One of the psychological shocks that most of us have to experience at some time is the death of a close friend or relative. If the death occurs very unexpectedly, the initial horror of the event may leave some one numbed, and the deep sadness may take some time to sink in. Even if the death expected the finality of bereavement is still an event that will change a person’s life and outlook.

These different shocks are the bumps and bruises that we all have to experience during life. If they are severe enough and a person is vulnerable, then they may take their toll and leave some psychological scar. But these events are not what shock means in the medical sense; it is something much more immediate and easy to recognize. The failure of the circulation is the basic problem, and treatment is in the province of the hospital physician or surgeon rather than the counsellor or psychiatrist.

WHAT IS SHOCK ?

Shock develops because of the way the heart and circulation work together. If for some reason the heart either fails to some reason the heart either fails to pump properly or there is not enough blood for it to pump, then in sufficient blood will be circulating to sustain the vital function of the body. This can be brought on by several things ranging from loss of large amount of blood to failure of the heart itself.

For the heart to pump in the correct manner it has to be primed with blood, and there has to be a certain amount of blood in the system for the heart to get up enough pressure to push the blood round. Normally, blood leaves the heart and travels out through the arteries until it gets to the tissues. In the tissues there are tiny arteries called arterioles, which have thick muscular walls.

If the pressure of the blood goes down, these arterioles can constrict (become narrower) so that there is less space than before. This system of constriction of the arterioles, called vaso-constriction, is the body’s way of maintaining the correct blood pressure when things go wrong. If the pressure falls too low, blood cannot flow around all the tissues. In fact, when the system fails – after excessive bleeding for example – shock develops.

CAUSES

Loss of blood after accidents is one of the commonest causes of shock. But trauma is not the only way in which large amounts of blood can be lost. It is not uncommon for there to be quite serious bleeding from ulcers in the stomach or the duodenum when large amounts of blood are either vomited or passed through the rectum. Patients with this sort of gastro-intestinal bleeding can arrive in hospital in a very shocked state. Another time of large blood loss can be during childbirth.

Some sorts of infection can also cause shock, although in this case the mechanism underlying the shock is different. Infection in the blood may lead to the production of toxins (poisons). These toxins seem to have a direct effect on the blood vessels in the tissues causing the venues (the very small veins) to become widened. Blood becomes pooled in the venues and not enough returns to the heart so it does not have enough to pump and so the blood pressure falls. This known as endotoxic or septicemia shock.

The other major cause of shock is when it results from disease of the heart itself. The main cause of this is an extensive heart attack. The heart muscle is destroyed by the heart attack and the more that is destroyed the more severe the effects of the attack will be. When more than 40 per cent has been destroyed, shock is likely to develop because the remaining heart muscle simply lacks the power to pump enough blood. This is called cardiogenic shock.

SYMPTOMS OF SHOCK

People with shock tend to have a similar appearance. They are pale and often cold and clammy to the touch; when the blood pressure is measured it is found to be very low – critically so.

The paleness is caused by the lack of blood in the skin – all the blood has been forced from the skin by the vasoconstriction. The coldness is also because the blood – which carries body heat – has been sent back into the core of the body.

It might seem strange that people are sweaty at the same time as being cold, but the autonomic nervous system, which is responsible for controlling the body’s unconscious functions, not only causes the vaso-constriction but also causes the adrenal glands to release adrenalin which in turn makes the sweat glands work. The trauma involved in shock stimulates the body’s ‘flight and fight’ response, one part of which is increasing sweating.

EFFECTS OF SHOCK

As well as the immediate, dangerous effects of shock – the prostration and grave illness – shock can create other, long-term problems. The two most important of these affect the kidneys and the lungs.

When shock develops and there is insufficient blood passing through the kidneys, acute renal failure can develop. The kidneys stop passing urine and waste products, particularly urea, a breakdown product of protein, start to build up in the blood. If the shock is dealt with relatively quickly, the kidneys are very likely to recover speedily. However, the process can be rather slow and dialysis may be required for days or even weeks.

But if shock has stopped the kidneys working, the situation may deteriorate even further. The blood supply to the brain may become inadequate and consequently, confusion and then unconsciousness may set in. The skin can sometimes progress from being cold and clammy and gangrene results because of the poor blood flow. When it has gone this far there is unfortunately very little hope for the patient.

The effect of shock on the lungs is a comparatively newly recognized condition. The effect, called shock lung, can occur even in apparently fit young people who have had large-volume blood transfusions following an event like a car accident. Patients who have this complication become breathless and the level of oxygen in the blood starts to fall. There is also extensive shadowing on chest X-rays.

What happens is that the lung acts as a filter to any abnormal substances circulating in the blood, and as it is common for transfused blood to contain a few little clumps of cells, these get caught up in the fine capillaries in the lungs and cause a blockage. This is a difficult condition to deal with and the basis of most treatment is to take over the function of the lungs by placing the patient on a ventilator or breathing machine.

TREATMENT FOR SHOCK

The aim of treatment of shock in all its forms is to try to return the volume of blood in the circulation to normal so that the heart can pump normally and an adequate amount of blood flow to the tissues. When blood loss has been the cause of shock then the treatment is simply a transfusion of the correct amount of blood to bring the volume back to normal. When the shock is due to septicaemia, the body still needs fluid even though the blood is pooled in the blood vessels. So here, clear fluids in the form of salt or sugar solutions, or protein containing fluids like plasma are used.

But there can be problems in giving large amounts of blood or fluid to older patients since these ‘extra’ fluids can overload the heart and lead to heart failure. Doctors have to get round this problem and to do this they have to keep a balance between having too much and too little fluid in the circulation. They measure this by checking the pressure in the part of the heart that ‘primes’ it – the right atrium.

This pressure measurement is called the central venous pressure (CVP). To take the pressure, a fine tube is passed into a vein in the arm or neck and the pressure is measured outside the body using a simple column of water. If the pressure is too high there is too much fluid; if it is too low there is not enough.

Shock caused by a heart attack - cardiogenic shock – cannot, however, be treated by a blood transfusion. Common forms of treatment include drugs which make the heart work harder and drugs which lessen the amount of work it has to do. But drugs that make it work harder can place an even greater strain on a heart weakened by an attack.

Fortunately there is one technique that gets round some of the problems. It uses a device called a balloon pump. A long sausage-shaped balloon is put at the top of the aorta, the biggest artery from the heart, and connected by a tube to a pump outside the body. The balloon is blown up between heartbeats and helps force blood out along the arteries. It thus reduces the amount of work the heart has to do while at the same time raising the blood pressure. The balloon deflates and allows the heart to pump more blood into the aorta then inflates, forcing blood around.

OUTLOOK

The outlook for the patient with shock depends a lot on the fitness of the person before the condition developed and on what was the cause of the shock.

A fit person who loses a lot of blood at a road accident but whose injuries are not too serious should do well after a blood transfusion and treatment for the physical damage. But an older patient who gets shock caused by infection after an operation is more at risk. Also someone who develops kidney failure or shock lung is in a much more risky situation. The outlook for the person with carcinogenic shock is very poor.