- The human brain functions at many
levels of consciousness. In the most basic terms, it is
"consciousness" that allows one to be aware of his world and
the world around him. Consciousness is fluid in nature, and
contains what we call "the mind", consisting of chains of
- Every day, our senses (touch,
sight, smell, taste, hearing) transfer information from the
outside world to the brain, using a cascade of electrical
impulses and chemical interactions. Yet despite such
observable functions, "the mind" as we know it is really
more a mental construct or idea that we loosely assign to a
series of phenomenon, than a definable concrete organ, like
the heart, liver, or lungs.
- Using previously recorded data
(i.e., memories, desires, fears, habits, language, past
response to pain, etc.), this entity known as "the mind"
attempts to make sense of the stream of incoming stimuli by
painting a picture on the "canvas of consciousness", from
which we may draw meaning, and form a "construct" (i.e., of
a tree, pain, love, etc.) of what we perceive, so that we
may react accordingly.
- Coma, quite simply, is a state of
prolonged "unconsciousness", in which one is not able to
respond appropriately to the incoming stimuli by reacting.
It is characterized by various stages of alertness and
function, with the deepest level nearly shut down. This is
the last step before so-called death and, interestingly,
resembles a deep sleep state from which one cannot be
aroused (even though some have).
- However, brain waves measured
during coma differ from those typical of deep sleep. And
while in coma, one may experience varying degrees of
awareness, but not be able to respond.
- Coma is also different from
stupor, a state in which an unconscious individual
eventually responds to repeated
- Depends on the stage
- How fast the coma develops depends
on the cause (e.g., in drug overdose it may develop
- Lack of self-awareness
- Unable to open eyes
- Unable to respond to painful
- Unable to speak
- Lack of purposeful movement
- There may be jerky movements of muscles, limbs,
- There may be tremors of muscles or limbs.
- There may be abnormal eye movements.
- Lack of normal sleep-waking cycle
- Impaired breathing
- May be unable to breath without
- Coma may last for months or years.
- Most patients die within the first
few weeks of hospital admission with
- Coma results from an insult or
injury to the brain that affects the structure or metabolic
activities of the brain. Damage is divided into two kinds --
those that occur inside the brain, and those that occur
- Intracranial (within the brain)
- Infections -- Meningitis, Encephalitis, Abscess
- Bleeding within the skull affecting the structure of
the brain -- intracerebral, subdural, subarachnoid,
- Tumors and brain swelling also have a mass effect on
- Stroke -- infarction or death of an
area of the brain
- Head Injury that leads to internal swelling, bleeding,
or hypoxia (depletion of oxygen)
- Cardiac Arrest -- deprives the
brain of oxygen
- Blood sugar variations -- Hypoglycemia or
- End stage liver disease -- Ammonia build up affects
- Kidney failure or uremia -- build up of toxic waste
normally excreted by the kidneys may affect the brain
- Endocrine deficiencies -- disorders of
hormone-producing glands, such as thyroid, adrenals, and
- Drug overdose -- alcohol, sedatives
- Diabetic Ketoacidosis -- build up
of ketones may affect the brain
- Electrolyte imbalances
- Carbon Monoxide Poisoning
- Very low or high body temperatures -- hypo- or
- Electrocution -- accidental exposure to high voltage
- Lead Poisoning, pesticide
- A medical history of medications,
diseases, past surgeries, injuries, psychiatric history,
occupation, habits, social history, and recent travels are
important in diagnosis -- family members may need to be
contacted for a full history.
- A physical examination from head to
toe is done to assess the stage and severity of the coma.
- The Glasgow Coma Scale (assigns a
score) describes the response to stimuli. The parameters
tested include the ability to open the eyes, response to
pain (movements or motor response), the presence or absence
of speech (verbal response), and its appropriateness. This
scale is more useful if done serially to assess progress,
rather than only once on admission.
- Breathing patterns, pupil size (e.g., pinpoint in heroin-induced coma), neurological findings (e.g., if one side of the body is paralyzed, there is a structural brain lesion), abnormal posturing of limbs, and fruity Breath Odor (as in
ketoacidosis) -- all of which may give clues to the cause of
- Labs include:
- Blood chemistries -- liver and kidney functions, Electrolytes (including Magnesium and Calcium), glucose,
Ammonia level, and toxicology screen
- Complete blood count and differential
- Blood gas analysis
- Urine for glucose and ketones
- May include a spinal tap
- CT scan or MRI of head
- Cerebral Angiography
- Coma is an emergency
- The first step is to support and
stabilize the vital signs, such as blood pressure,
breathing, and temperature.
- Intravenous (IV) fluids are started
immediately, and all patients receive Dextrose (glucose
solution), Naloxone (antagonist to opiate drugs such as
heroin) and Thiamine (B vitamin), unless contraindicated.
- Oxygen is given to all patients in
coma. Respiratory support using mechanical ventilation may
be needed if the patient is not breathing.
- Patient is transferred to an
intensive care unit to be monitored.
- Measures must be taken to prevent complications of prolonged immobility (e.g., Bed Sores, limb
- In patients who do not recover from
coma, family members, physicians, psychologists, and social
workers may need to meet and discuss "quality of life
issues" (e.g., should the patient be resuscitated if the
heart suddenly stops).
- Family members and friends of the
patient should ask the doctors they know for any new
treatments or ongoing clinical trials.
- See causes
- Psychiatric illnesses such
- Conversion reactions
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