Coma and unconsciousness

 

Coma ( or unconsciousness ) is a state in which a patient is totally unaware of both self and external surroundings, and unable to respond meaningfully to external stimuli.

Coma results from gross impairment of both cerebral hemispheres, and/or the ascending reticular activating system.

There are many causes of coma (including Newcastle Brown Ale ), and these may be classified as either focal or diffuse brain dysfunction.



Focal brain dysfunction

- brain tumour

vascular events (CVA)

demyelination

infection, such as cerebral abcess

focal head injury

 

Diffuse brain dysfunction

infection, such as meningitis or encephalitis

epilepsy

hypoxia and hypercarbia

drugs, poisoning and overdoses ( including alcohol)

metabolic/endocrine causes, such as diabetic coma, hepatic or renal failure, hypothyroidism, severe electrolyte disturbances

hypotension, or hypertensive crisis

diffuse head injury

subarachnoid haemorrhage

hypothermia, hyperthermia

sometimes, people just pretend !

However, even if you have just learned this list, from a clinical point of view it is very much of secondary importance. When confronted by a potentially unconscious patient, what do you do?

 


Management of the unconscious patient

First of all, make sure quickly that they are unconscious, and not just asleep. Often, someone else has already done this for you. Next, the primary care is EXACTLY the same as Basic Life Support – AIRWAY, BREATHING, CIRCULATION.

A patient who is unconscious is at a very high risk of compounding their problems by adding to them by asphyxia, leading to death. When consciousness is lost, the tongue usually falls back in the pharynx and obstructs the airway. The cough reflex is lost, and blood or regurgitated stomach contents are often aspirated into the lungs. Therefore, the unconscious patient must have their airway supported by tilting the head and lifting the chin ( sometimes with the help of an oral or nasal airway ), and by placing them into the coma position to prevent aspiration. They must be checked frequently to make sure they are breathing freely, by:

Look – watch the chest moving easily, without the use of accessory muscles or the abdomen heaving.

Listen – with you ear at the patient mouth, or with a stethescope

Feel – the flow of air at the mouth with your hand or cheek, and chest or abdominal movements.

 

Alternatively, they may have an endotracheal tube placed, preferably by an anaesthetist. All unconscious patients should be given supplemental oxygen therapy at a high concentration. VERY FEW PATIENTS HAVE END STAGE OBSTRUCTIVE AIRWAYS DISEASE AS THE CAUSE OF THEIR COMA. Therefore, give more than 24% oxygen !!!

The circulation in the unconscious patient often requires support, and so early good intravenous access is required, with measuring of the pulse and blood pressure and appropriate treatment.

Early consultation with senior medical staff and intensive care is important in providing optimum care for the unconscious patient. Once the ABC is sorted out, you can move onto D (diagnosis), E (evaluation) and F (further management).

Diagnosis

If available, the history from relatives or ambulance staff will often give all the necessary clues needed to make a provisional diagnosis of the cause of unconsciousness. However, if they are a pyrexial, depressed epileptic diabetic that has been unwell recently and then fallen down stairs………..

Making a diagnosis is important, because it will direct appropriate therapy. However, it does not reduce the need for generic supportive care, such as that offered on intensive care. Sometimes, the diagnosis allows the withdrawal of care, if the cause of coma is untreatable and the brain damage irreversible.

 Evaluation

The comatose patient should be physically examined for any helpful signs, such as lumps on the head and non blanching rashes. The system which will be examined most intently ( and often provides the least information) is the nervous system. There are certain parts of the central nervous system which are easy to examine, including the eyes and reflexes, but other information is provided by the posture and muscle tone, and the respiratory pattern. The eyes do give useful information – pupil size and equality, and direction of gaze.

A truly comatose patient is deeply unconscious, with no response to pain. However, it is often found that patients are not completely unconscious, and so can be categorised onto a point on a "coma scale". Here is an example of a simple 5 point scale:

1 = fully awake

2 = conscious but drowsy

3 = unconscious but responsive to pain with purposeful movement e.g. flexion/withdrawal

4 = unconscious but responding to pain by extension

5 = unconscious and unresponsive to pain

 

This scale gives a simple measure of the degree of unconsciousness, but disregards other information that may be available. The most commonly used complex scale, using three groups of observations, is the Glasgow Coma Score, which was originally suggested for the assessment of head injury patients. This looks at eye activity, verbal and motor responses, and assigns points for each to give a composite score, 3 being deeply unconscious and 15 being fully conscious:

POINTS

 

Best motor response

Movement in response to command 6

Localizes pain 5

Withdraws from pain 4

Flexes in response to pain 3

Extends in response to pain 2

No response 1

 

Best verbal response

Fully orientated 5

Confused 4

Inappropriate words 3

Incomprehensible sounds 2

No response 1

 

Best eye response

Eyes open spontaneously 4

Eyes open to command 3

Eyes open in response to pain 2

Eyes remain closed 1

Next time you and your friends get back from the pub, why not check each others coma score?

These scales and scores are most useful in allowing the assessment of changing levels of consciousness, either improvement or deterioration. A worsening of the GCS in a head injured patient indicates the need for urgent neurosurgical intervention.

There are other coma scales, which apply to specific types of coma, such as that found in hepatic failure:

Stage 1: impaired personality or thinking. EEG usually normal

Stage 2: confusion, abnormal sleep and drowsiness. Asterixis and increased reflexes, with plantar responses up or down. EEG abnormal.

Stage 3: marked confusion, with inability to perform fine movement. Responds to painful stimuli

Stage 4: comatose with depressed reflexes

These problems in hepatic failure are caused by cerebral oedema, due to problems such as hypoglycaemia, hyponatraemia, hypokalaemia, hypothermia, respiratory and renal failure.

 

Investigations

A full blood count, and simple biochemistry, give lots of useful information which may make the diagnosis. Other simple tests often useful in diagnosis of unexplained coma include blood sugar, paracetamol and aspirin levels.

An investigation which is used increasingly, and often without a proper physical examination of the patient, is the computerised tomogram of the head, the CT scan.

The procedure puts the patient at some risk while in the scanner, but it does give quite a lot of information about what is going on inside the head. It will show space occupying lesions, bleeds and swelling of the brain. Often the CT scan does not help, except as a route of exclusion. There is a more sophisticated scan available, the MRI, which shows similar things but in better detail. They take longer and are less readily available, and are so not used in the acute stages of management very often.

Lumbar puncture is often undertaken, and will give information about infection or bleeding ( the CSF becomes xanthochromic – yellow ).

If no diagnosis is still apparent, then just about every other test available will then be used in whatever order comes into the clinician’s head, although sometimes the choices are based on presumed diagnoses.

The EEG may give useful information, especially if epilepsy is suspected.

 

Further Management of the comatose patient

This care will often be delivered in a specialist unit, usually an intensive care/therapy unit. Long term management involves consideration of the problems suffered by a patient lying still for very prolonged periods with no protective reflexes. These include

pressure area care

care of the mouth, eyes and skin

physiotherapy to protect muscles and joints

risks of deep vein thrombosis

risks of stress ulceration of the stomach

nutrition and fluid balance

urinary catheterization

monitoring of the CVS

infection control

maintenance of adequate oxygenation, with the assistance of artificial ventilation

 

 

When is Coma not Coma ?

Often, if the causes of coma are not treated, or cannot be treated, then it will progress to the point of irreversible brain damage and then brain death.

Brain death is more correctly described as brain stem death. What we look for is the absence of the activity in the brain stem that is required for the survival of the body, most importantly breathing. The tests we do for brain death are looking at the integrity of brain stem reflexes.

Before we can commence the tests we must have a patient with a known irresversible cause of coma, and we must exclude:

any drugs which may be causing CNS depression, or paralysis

any endocrine or metabolic disturbances causing CNS depression

hypothermia ( temperature of less than 35 degrees C )

Then, what we look for are:

absent pupillary response to light

absent corneal reflex

absent oculovestibular reflex ( nystagmus in response to cold water in the ear)

absent motor responses to pain

absent cough and gag reflexes

absent respiratory efforts, despite adequate stimulation from carbon dioxide in the blood.

These tests are done by two senior doctors, and usually performed twice. One done, the patient is "dead", and can be an organ donor if suitable. If the patient breathes, they are not brain dead, but in a persistent vegetative state which can potentially go on for years.

Dr Gary Enever, October 1999. Return to previous page