Coma (cont.)
Hypoglycemic coma
All cells in the body need glucose and oxygen to perform their functions by
aerobic metabolism (aerobic= with oxygen). While other parts of the body can
continue for short periods of time anaerobically (an=without + aerobic+oxygen),
the brain cannot. Without glucose, the brain stops.
Hypoglycemia (hypo=low + glyc=glucose + emia= blood) most often occurs in
people with diabetes who have given themselves too much insulin or have not
taken in enough food.
In normal physiology, the pancreas makes insulin and balances the amount it
produces with the amount of glucose in the blood stream. Diabetics need
to inject insulin into their body, or take medication to stimulate the pancreas
to make insulin. Monitoring blood sugars is critical to avoid hypoglycemic coma.
Poisons
There are two sources of poisons that can affect the brain, those that we
take in (through ingestion or inhaling) and those that the body generates and cannot
dispose of in some way.
If the body can be considered a factory, it needs to have the ability to get
rid of the waste products that are made when the body generates energy. These
waste products can cause different organs in the body to fail, including the
brain.
The liver performs many functions including glucose and protein
manufacturing. It also breaks down and metabolizes chemicals in the body. When
the liver fails different chemicals like ammonia can accumulate and can cause
brain cells to stop functioning. Hepatic encephalopathy (hepatic=liver +
encephalo=brain + pathy=disease) or hepatic coma occurs when the liver fails
because of an acute or chronic injury. The most common is
cirrhosis due to
alcoholism.
The kidneys filter blood to rid the body of waste products. When the kidneys fail, a variety of waste products can accumulate in the bloodstream and cause
direct or indirect damage to the brain. An example of indirect causes would be
an elevated potassium level affecting heart electrical activity. Direct causes
include uremia, where blood urea levels rise and are directly toxic to brain
cells. Common causes of kidney failure include poorly controlled diabetes and
high blood pressure.
The thyroid acts as the thermostat for the body and regulates the speed at
which the body functions. If thyroid levels drop too low, gradually, over a period
of time myxedema coma can occur because of profound hypothyroidism.
Ingestions can cause the brain to slow down, speed up or alter its perception
of the world. Some ingestions may cause coma in an indirect way. Acetaminophen
is a prime example, an overdose may cause the
liver to fail and few days
later subsequent hepatic coma occurs.
Alcohol is probably the most common cause of ingested poison or toxin,
leading to altered mental status and coma. In acute alcohol intoxication, the
brain is directly poisoned. Blood alcohol levels fall when metabolized
by the liver, but depth of intoxication can be so great it shuts off
many of the involuntary brain activities that control breathing and maintain
muscle function. Opiates like pain pills or heroin can cause similar slowing of
brain function.
Cocaine and amphetamines are the common "uppers" or brain stimulants. These
brain stimulants
cause an adrenaline-like body response, thus blood pressure and heart rate
spiral out of control and the risk of
heart attack, heart
rhythm disturbances, or bleeding in the brain occur.
Next: How is coma assessed? »
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