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Fluids &
Electrolytes
The
electrolyte panel is used to detect, evaluate, and
monitor electrolyte imbalances. It may be ordered as
part of a routine exam or to help evaluate a chronic or
acute illness. It may be ordered at intervals to help
monitor conditions, such as kidney disease and
hypertension, and to monitor the effectiveness of
treatment for known imbalances.
As part of routine health
screening, when your doctor suspects that you have an
excess or deficit of one of the electrolytes (usually
sodium or potassium), or if your doctor suspects an
acid-base imbalance.
Electrolytes are electrically charged minerals that are
found in body tissues and blood in the form of dissolved
salts. They help move nutrients into and wastes out of
the body’s cells, maintain a healthy water balance, and
help stabilize the body’s pH level. The electrolyte
panel measures the main electrolytes in the body: sodium
(Na+), potassium (K+), chloride (Cl-), and carbon
dioxide (total CO2).
The Fluids & Electrolytes Panel includes:
Sodium, Serum - One of
the major salts in the body fluid; sodium is important
in the body's water balance and the electrical activity
of nerves and muscles.
Sodium is a mineral that is vital to normal body
function. It is an electrolyte, a positively charged
molecule that works with other electrolytes, such as
potassium, chloride and total carbon dioxide ( CO2), to
help regulate the amount of fluid in the body. Sodium is
present in all body fluids but is found in the highest
concentration in the blood and in the fluid outside of
the body’s cells. We get sodium in our diet, from table
salt (sodium chloride or NaCl), and to some degree from
most of the foods that we eat. Most people have an
adequate intake of sodium. The body uses what it
requires and the kidneys excrete the rest in the urine
to maintain sodium concentration within a very narrow
range. It does this by: producing hormones that can
increase (natriuretic peptides) or decrease (aldosterone)
sodium losses in urine, producing a hormone that
prevents water losses (antidiuretic hormone [ADH]), and
controlling thirst. (Even a 1% increase in blood sodium
will make you thirsty and cause you to drink water,
returning your sodium level to normal.)
Abnormal blood sodium is usually due to some problem
with one of these systems. When the level of sodium in
the blood changes, the water content in your body also
changes. These changes can be associated with
dehydration or excess fluid (edema), especially in the
legs.
Chloride, Serum - Similar
to sodium, it helps to maintain the body's electrolyte
balance.
Chloride is an electrolyte, a
negatively charged molecule that works with other
electrolytes, such as potassium, sodium, and total
carbon dioxide (CO2), to
help regulate the amount of fluid in the body and
maintain the acid-base balance.
Chloride is present in all body fluids but is found in
the highest concentration in the blood and in the fluid
outside of the body’s cells. Most of the time, chloride
concentrations mirror those of sodium, increasing and
decreasing for the same reasons and in direct
relationship to sodium. When there is an acid-base
imbalance, however, blood chloride levels can change
independently of sodium levels as chloride acts as a
buffer. It helps to maintain electrical neutrality at
the cellular level by moving into or out of the cells as
needed.
Chloride is taken into the body through food and table
salt, which is made up of sodium and chloride molecules.
Most of the chloride is absorbed by the gastrointestinal
tract, and the excess is excreted in urine. The normal
blood level remains steady, with a slight drop after
meals (because the stomach produces acid after eating,
using chloride from blood).
Potassium - Helps to
control the nerves and muscles. Potassium is an
electrolyte, a positively charged molecule that works
with other electrolytes, to help regulate the amount of
fluid in the body, stimulate muscle contraction, and
maintain a stable acid-base balance. Potassium is
present in all body fluids, but most potassium is found
within your cells. Only about two percent is present in
fluids outside the cells and in the liquid part of the
blood (called serum or plasma). Because the blood
concentration of potassium is so small, minor changes
can have significant consequences. If potassium levels
go too low or too high, your health may be in
considerable danger: you are at risk for developing
shock, respiratory failure, or heart rhythm
disturbances. An abnormal concentration can alter the
function of neuromuscular tissue; for example, the heart
muscle may lose its ability to contract.
CO2 -
The CO2 test measures the total amount of carbon dioxide
in the blood, mostly in the form of bicarbonate (HCO3-).
Bicarbonate is a negatively charged electrolyte that is
excreted and reabsorbed by the kidneys. It is used by
the body to help maintain the body’s acid-base balance
(pH) and secondarily to work with sodium, potassium, and
chloride to maintain electrical neutrality at the
cellular level. Since the CO2 test measures all three
forms of carbon dioxide in the blood (bicarbonate, H2CO3
[also known as carbonic acid], and dissolved CO2) as a
total CO2, it will give a rough estimate but not an
exact determination of the bicarbonate concentration.
When
CO2 levels are higher or lower than normal, it suggests
that your body is having trouble maintaining its
acid-base balance or that you have upset your
electrolyte balance, perhaps by losing or retaining
fluid. Both of these imbalances may be due to a wide
range of dysfunctions.
Some
drugs may increase blood carbon dioxide levels
including: fludrocortisone, barbiturates, bicarbonates,
hydrocortisone, loop diuretics, and steroids.
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