A coma is defined as a ‘profound state of unconsciousness’ wherein a person is unable to be wakened. They will not respond to pain, light, sound or other stimulation, and they will not have the usual ‘sleep-wake cycles’. Someone in a coma is described as being ‘comatose’.
There are many different conditions that can result in coma. These include intoxication, brain injury, stroke, hypoxia, metabolic abnormalities, low blood sugar, increased carbon dioxide and more. It is also possible to induce a coma which can be used to slow the progress of illnesses and conditions, and to prevent suffering while the patient is treated. This is achieved by pharmaceutical agents who suppress the higher brain functions.
When uncontrolled a coma can be a serious condition that causes brain damage if it continues for more than three days depending on the underlying cause. Low blood sugar (hypoglycemia) or hypercapnia (increased carbon dioxide) can both lead to coma, but are less likely to cause severe brain damage. In some cases the brain damage itself is what causes the coma. In cases of encephalitis (swelling of the brain), brain damage can be caused by the brain swelling and then pressing up against the inside of the skull where it can become damaged. In cases where the individual is starved of oxygen this may also lead to brain damage.
Levels of Coma
Likewise there are varying levels of coma and these are measured on various scales such as the Glasgow coma scale. When an individual is deep in coma they are at risk of asphyxiation as they lose control of their basic bodily functions controlled by their brain stem. Scales such as the Glasgow coma scale can be used in order to assess the amount of risk of this happening, and if it is deemed to be a high risk then the doctors will seek to aid the individual in their breathing with something such as an oropharyngeal airway.
Following are the stages of the Glasgow coma scale, which look at the ability to see and recognise visual stimuli, make sounds and control motor movements. The scale awards ‘points’ for abilities in these capacities where the lower the points the worse the condition. The lowest score is ‘3’ which is considered ‘deep coma’ or death.
1 – Does not open eyes
2 – Opens eyes during painful stimuli
3 – Opens eyes in response to voice
4 – Opens eyes spontaneously
1 – Makes no sound
2 – Incomprehensible sound
3 – Inappropriate words (random or involuntary speech, often exclamatory)
4 – Confused speech
5 – Oriented speech and ability to respond appropriately to questions
1 – No motor response
2 – Motor extensions in response to pain
3 – Abnormal flexion to pain
4 – Withdrawal in response to pain
5 – Localised movements to pain
6 – Obeys commands (such as ‘move your left hand’)
Another scale is the Ranchos Los Amigos Scale, and individuals may or may not ‘progress’ through these scales in either direction.
If an individual progresses to a vegetative state, they have entered a state of extreme brain damage, but have regained partial awareness. After a few weeks of being in a vegetative state the condition will be classed as a ‘persistent vegetative state’ and after a year of PVS they will be considered as being in a ‘permanent vegetative state’. This can be considered a ‘wakeful unconsciousness’, it is not recognised legal death, though in some cases life support may be terminated if the individual has entered an irreversible vegetative state though this is a highly controversial legal issue. In other cases the families of the patient may choose to care for the patient and in some rare cases families choose to treat them as disabled family members in the hope that talking to them and including them in activities might result in some level of recovery.
Usually a patient in a vegetative state will be able to open their eyes, swallow and respond to pain and other sensations. They may also be able to track movements with their eyes, and may scream, laugh or cry at seemingly random intervals which can be highly distressing and confusing for a hopeful family. They usually require no life support other than a feeding tube as their brain stem which controls bodily functions such as breathing will remain intact.
Diagnosis and Treatment
Normally coma is a result of bilateral damage (damage to both sides) to the reticular formation of the hindbrain, an area used in our basic functions. When a person’s condition is stabilised, the medical professions will then assess the underlying cause using computed tomography of the brain, or other brain imaging techniques to identify the appearance of a hemorrhage etc. This might then require surgery or other treatment.
The patient will normally require generic treatment in order to support them during coma – for example they might require nutrients if they are unable to eat, or they may require mechanical breathing aids if they are in deep coma and at risk of asphyxiation. Again this will depend on the specific case.
The outcome after a patient has entered a comatose state varies widely. Comas will tend to last a few days or a few weeks, though in rare cases they can sometimes last for several years. Normally patients will gradually come out of the coma, progressing through the coma scales and re-acquiring basic movements and responses, though in other cases they may progress to a vegetative state.
The prognosis for coma or a vegetative state depends on the cause, the location and the severity of the brain damage that has caused the coma. The deeper levels of coma are not necessarily linked to a lower chance of recovery. Statistical analysis can be used to predict roughly the chances of recovery in individual coma cases. As time progresses however, the chances of recovery become slimmer – after four months of coma caused by brain damage for instance, the chances of recovery are generally a low as 15%. Death can also occur as a result of secondary infections such as pneumonia, or through asphyxiation, and this can occur before the patient has had a chance to recover fully. In rare cases individuals can recover after extended periods of time, for example one patient ‘Terry Wallis’ regained consciousness and the ability to speak and respond to his awareness after 19 years. These however are highly rare cases.
When the individual recovers, they will often have a range of cognitive and physical difficulties. The return of consciousness is something which often happens gradually, with patients slowly regaining certain responses and abilities. They will usually wake in a profound state of confusion and may be unable to form sentences or control their movements. More complex motor tasks such as walking and talking coherently will certainly require training and may never recover if the patient has suffered brain damage during their coma.