UNCONSCIOUSNESS

Slipping into the dark world of oblivion can be a dangerous journey. Brought on by a variety of causes, unconsciousness ranges in severity from a fleeting faint to a life-threatening or permanent coma.

Normal consciousness may be defined as the state in which a person is awake, alert and aware of his surrounding environment. Unconsciousness is a sleep-like state, but much deeper, with the person having no awareness of his surroundings and showing no response to any stimuli. This condition can vary in severity, ranging from a transient faint to a prolonged coma. Whatever its immediate cause, the condition only arises because of important changes in the brain.

MECHANISM IN THE BRAIN

Exactly how the brain functions in consciousness and unconsciousness is not yet fully understood. However, there are a number of critical areas in the brains that

are deeply involved in maintaining consciousness. These are the cerebral cortex, the thalamus. the brain-stem and, in particular, a group of cells within the brain-stem called the reticular formation.

The cerebral cortex receives sensory inputs from the main sensory nerves and also from the reticular formation. Nerve routes from around the body branch out to the reticular formation and feed it a constant stream of electrical signals. This action, in turn, causes the reticular formation to fire off signals to targets all around the brain, to the appropriate centres where the signals are gathered. collated and acted upon. If this driving force slows down. or is prevented from occurring. the cerebral cortex becomes sleepy'. and we become unconscious.

The brain-stem is also important in that it is responsible for keeping our essential body mechanisms - such as heartbeat, blood pressure and breathing - running smoothly without our even having to think about it.

It appears that when a person becomes unconscious - for whatever reason - the brain concentrates itself on keeping the body ticking over by using all available energy in keeping the brain-stem functioning. Damage is thereby confined to what are regarded as 'non-essential' parts of the brain.

DEGREES OF UNCONSCIOUSNESS

The brain's activity can be measured as electrical impulses on a machine called an electroencephalograph, or more simply an EEG. The impulses of the brain are presented as a pattern of electrical waves. This pattern varies considerably according to the degree of alertness or unconsciousness, thus providing a clue to the severity of the unconscious state a person may be in. For instance, during unconsciousness, the pattern of waves is slow and large, about three waves present each second. When someone is coming round from unconsciousness - or rousing from sleep - the waves come at about six to eight a second, and increase in frequency until, at full consciousness. the pattern of waves is rapid and, jagged. showing increased electrical activity.

The machine is used to determine whether the brain has been severely damaged or even 'died'. If the EEG shows no electrical activity, then the person has almost certainly suffered brain death.

CAUSES

Unconsciousness can be caused by a variety of factors, ranging from shock to poisoning. The most likely cause that we are likely to come across is syncope, known as fainting.

Fainting can be brought on by anything from excessive heat to standing still for long periods, conditions which result in a temporary lack of blood supply to the brain. The resultant lack oxygen forces the brain to 'shut down' for a brief spell until the oxygen supply is restored to normal levels. If, for some reason, the blood supply to the brain is not fully and quickly restored the person may enter a deeper state of unconsciousness.

Symptoms of fainting include dizziness, light-headedness and a lack of colour in the face. Someone who has fainted should remain lying down for a few minutes until a full recovery has been made., Allowing a person who has fainted to get up too soon, or pulling him to his feet, could result in a more serious unconscious state.

Poisoning by fumes, chemicals or drugs can also cause unconsciousness, though by different means. For instance, barbiturates depress the central nervous system, in which case the brain-stem mav be affected, necessitating emergency measures to ensure the maintenance of the life-support systems. Stimulants will be given to treat' this form of poisoning when it has led to unconsciousness.

Carbon monoxide poisoning, however, replaces the oxygen in the blood which leads to an oxygen deficiency at the brain. Immediate treatment consists of removing the person from the source of the gas and artificial respiration.

Shock can bring on unconsciousness through a collapse of the circulatory system. Once the circulatory system fails to maintain an adequate supply of blood to the brain, then the collection of symptoms known as shock syndrome becomes apparent. This will include sweating, blurring of vision, shallow, rapid breathing and faintness that can drift into unconsciousness.

Shock like this can be brought on by extensive internal or external bleeding, heart attacks and loss of body fluid due to various illnesses. In cholera, for example, the body becomes so dehydrated that the sufferer actually dies of shock rather than the virus.

Treatment of shock varies according to the cause. Replacing lost fluid and raising the blood pressure are measures taken in hospital, but it is important to try to stop heavy bleeding as soon as possible. If the patient becomes unconscious, turn him on his side and make sure that he can breathe properly. If breathing stops then artificial respiration should be given.

Head injuries are a common cause of unconsciousness and they occur in many sports like rugby and boxing. Unconsciousness may be brought on either through direct injury to brain tissue or through a temporary contraction of blood vessels, which impairs brain function. This condition is known as concussion. and varies considerably in the degree of severity. A return to consciousness may be accompanied by a severe headache, nausea and difficulty in focusing the eyes.

Loss of memory of what happened immediately prior to the injury also occurs, and is one of the main symptoms of concussion. Any one who has been knocked out should see the doctor as soon as possible as there could be a chance of skull damage or internal bleeding.

Epilepsy can also cause unconsciousness and is usually accompanied by convulsions. Quite why the fit takes place is not fully understood, but it is known that it is brought on by an uncontrollable discharge of electricity by the brain .

COMA

A coma is the most extreme form of unconsciousness, a state that is very serious and often long-lasting. Unlike in sleep, the activity of the brain as a whole is depressed, and even reflex actions like coughing, corneal reflexes and tendon reflexes - are absent. In the very deepest comas, the person may not respond even to the most painful stimuli.

The usual causes of coma are injury to the brain severe shock and blood poisoning. Damage to the thalamus may initiate a permanently comatose state. Both diabetes and hypoglycemia are also common causes of a coma, but thankfully can be controlled.

Previously, any kind of coma that lasted for more than 24 hours usually resulted in permanent brain damage, but modern treatment and nursing has done much to change this. However, the longer a coma lasts, the less likelihood there is that a perfect recovery can be made.

In all cases of unconsciousness, treatment depends on the underlying cause, and may range from simple rest and recuperation to surgery. A comatose patient will require long-term care.