A coma is a state of unconsciousness where a person is unresponsive and cannot be woken.
A severe head injury or a condition that affects the brain, such as a stroke, are two possible causes of a coma.
A person can also be in a coma as a result of alcohol intoxication. Extreme changes in blood sugar levels in people with diabetes – either very low blood glucose levels (hypoglycaemia) or very high blood glucose levels (hyperglycaemia) – can also cause coma.
You may find the following information useful if you have a friend or a loved one who is in a coma. It covers:
what a coma means
caring for and monitoring a person in a coma
what you can do as a visitor
recovering from a coma
support and more information
What a coma means
Someone who is in a coma has minimal brain activity. They're alive, but can't move or be woken. Their potential for recovery will depend on the cause of the coma.
A person in a coma will often be unresponsive to their environment. They may not be able to hear voices or feel pain. However, they may have some awareness of their surroundings. Every coma experience is unique.
Occasionally, a person in a coma may open their eyes, grimace or make a noise. They may not be aware of these movements or have any control over them.
Being in a coma means the person has a low level of consciousness. Their level of consciousness will depend on how much of their brain is functioning, which may change over time.
For example, initially a person may be in a very deep coma, where they're unresponsive to pain, before gradually recovering to a lighter coma, where they respond to pain. They may continue improving and eventually may become aware of their surroundings and begin to communicate.
The ability to make a clearly conscious response to external instructions indicates that the person is no longer in a coma.
Caring for and monitoring a person in a coma
Doctors score a person's level of consciousness using a tool called the Glasgow Coma Scale. This level is monitored constantly for signs of improvement or deterioration. The Glasgow Coma Scale assesses three things. They are:
eye opening – a score of one means no eye opening, and four means opens eyes spontaneously
verbal response to a command – a score of one means no response, and five means alert and talking
voluntary movements in response to a command – a score of one means no response, and six means obeys commands
A higher score on the scale suggests that less brain function has been lost. A score of eight or less often means that someone is in a relatively deep coma.
While someone in a deeper coma generally has a poorer outcome, the cause of the coma is important in determining their recovery. For example, a young person who took an alcohol or drug overdose may be deeply comatose to begin with, but may make a very good recovery with the appropriate medical care.
A person in a coma may be unable to maintain normal body function. For example, they may not be able to breathe unaided and their blood pressure may be unstable.
Caring for a person in a coma involves ensuring that their condition is stable and their body functions, such as breathing and blood pressure, are supported while the underlying condition is treated.
Healthcare staff will try to prevent infections, provide good nutrition and prevent bedsores by moving the person's position regularly.
In the early stages, most people in a coma will be cared for in an intensive care unit (ICU).
What you can do as a visitor
The experience of being in a coma differs from person to person, and also depends on how deep the coma is.
Some people remember events that happened around them while they were in a coma, while others don't. Most memories are likely to relate to the period when the person comes out of the coma.
Some people have reported feeling enormous reassurance from the presence of a loved one when coming out of a coma.
When visiting a friend or loved one in a coma, you may find the advice below helpful.
when you arrive, announce who you are and try to always speak positively
talk to them about your day as you normally would
be aware that everything you say in front of them might be heard
show them your love and support – even just sitting and holding their hand can be a great comfort
you could play them their favourite music through headphones
Recovering from a coma
A coma can last hours, days or even months. Some people remain in a coma for years, although this is unusual.
Recovery depends on how much of the person's brain has been affected by the underlying condition or injury. Generally, the longer the person has been in a coma, the poorer the outlook.
People don't usually suddenly "wake up" from a coma, but tend to come round gradually and regain brain function over time. When a person comes out of a coma, they may be agitated and confused. They may need to be sedated for their own safety.
Some people will make a full recovery and be completely unaffected by the coma. Others may not be able to do some of the things they used to do and may need to have physiotherapy, occupational therapy and psychotherapy during a period of rehabilitation. They may need care for the rest of their lives.
Some people who recover from a coma will be in a vegetative state. They may be able to open their eyes and appear to be awake, and they may recover basic functions, such as breathing unaided and controlling their blood pressure. However, someone who is in a vegetative state will have lost a substantial amount of brain function and be unaware of their surroundings.
Further information and support
For further information and support from healthcare professionals and the families of people in a coma, you may find the following resources helpful:
Headway: the brain injury association
ICUsteps: the intensive care patient support charity
A person in a coma will often be unresponsive to their environment
One man's account of being in a coma
"For much of the time I knew what was going on. I couldn't see, but I could feel and hear. I knew what was in the news and, when I awoke, could repeat anecdotes that had been recounted to my apparently deaf ears.
"I remember being told what the doctors thought was wrong and consciously setting out to fight it. I once overheard a discussion about how seriously ill I was.
"The nurses would say that they were going to give me an injection or take my blood pressure before I felt the needle going in or the tourniquet tightening.
"I could also feel my dear wife's hand in mine, our fingers entwined. I could hear her telling me that the children were all right and that their schools and my office were being supportive. I couldn't work out what she was doing in the strange world I now inhabited, but her presence was enormously reassuring."
(This is an edited version of an original account that appeared in The Independent, September 2006.)