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What is a Coma?

What does it mean for someone to be in a coma? What causes a coma? What is the test for coma? Can a person in a coma be an organ donor? We’re here to answer your questions.

A coma is a prolonged state of unconsciousness where the brain is functioning at its lowest level of alertness. While in a coma, a person will not respond to voices or any activity in their surroundings. A person in a coma is alive and looks like they are sleeping. However, the person cannot be shaken awake, and does not respond to any stimulation, including pain.

Coma is a medical emergency. Immediate action is needed to preserve life and brain function. A coma rarely lasts longer than several weeks but recovery from coma is gradual. People who are unconscious for longer than several weeks might transition to what is called a persistent vegetative state or even brain death.

What Causes a Coma?

Comas are caused by an injury to the brain. Some things that could cause a coma are:

  • traumatic head injury
  • stroke or seizure
  • brain tumor
  • infections involving the brain
  • brain damage caused by a prolonged lack of oxygen
  • an overdose (taking too much) of medicine or other drugs
  • chemical imbalances caused by an underlying illness

Testing for Coma

Identifying when a person is in a coma requires thorough testing. This will often involve three types of test: physical examination, laboratory tests, and brain scans.

Physical examination checks things such as reflexes, response to pain, vocal noises and observing eye reactions. For example, physicians might squirt cold water into the patient’s ear canal and monitor for eye movement or a reflexive response.

Laboratory tests will check blood for things like glucose, liver and kidney function, carbon monoxide poisoning and drugs or alcohol. A spinal tap may also be given to find infections in the nervous system.

Brain scans give physicians images of the brain to help identify the areas that are injured. Tests might include a CT scan to get a detailed image of the brain; MRI to see if there is tissue damage and EEG to detect activity in the brain.

Can a Person in a Coma Be an Organ Donor?

No. A person in a coma cannot be an organ donor.

Only when a person is on ventilated support, has experienced brain death and the time of death has been noted can they be considered for organ donation.


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