Dehydration occurs when the total body water
is less than normal. Usually it involves loss of both water
and electrolytes, which are minerals such as sodium, chloride
and potassium. During illness, dehydration may be caused by an
inadequate fluid intake. Fever increases the loss of water.
When there is not enough body water, fluid shifts out of the
body cells to compensate, leaving the cells deficient in
necessary water. This leads to dehydration. The severity of
the dehydration is based on the magnitude of these body water
shifts. Dehydration is caused by either a lack of food or
water intake or an increase in water loss through illness or
injury.
What to Watch For
Signs of dehydration include:
Loss of skin elasticity
Lethargy
Depression
Sunken eyes
Dry gums
Increased heart rate
Slow capillary refill time
Diagnosis
Physical examination findings can help determine if
dehydration is present. A common but inaccurate way to
diagnose dehydration is based on skin elasticity. When the
skin along the back is gently lifted, it should immediately
return to the normal position. In a dehydrated animal, the
skin does not return to normal quickly. The speed of return to
normal position can help determine the severity of the
dehydration.
Blood tests such as a complete blood count and biochemistry
profile are important to try to find the underlying cause of
the dehydration but may not reveal if dehydration is present.
The most important tests are a packed cell volume and total
blood protein test. These tests are done on a blood sample and
can help reveal if dehydration is present.
If the packed cell volume and total protein are elevated,
dehydration is present. Determining the concentration of the
urine can also help determine if the pet is dehydrated and if
the kidneys are affected.
Treatment
The treatment for dehydration is to supplement the body with
fluids. It is often not possible for an ill pet to ingest
sufficient water to correct dehydration. Fluids are typically
administered as an injection. The most efficient method of
rehydration is through intravenous fluids. This requires
hospitalization as well as an intravenous catheter.
Fluid replacement is done slowly to allow the body to
compensate and slowly replenish tissues starved of fluid.
Home Care and Prevention
There is no home care for dehydration. If you suspect that
your pet is dehydrated, prompt veterinary care is recommended.
Some animals can be treated with subcutaneous fluids at home,
after an initial diagnosis and treatment. Ask your
veterinarian if this is an option and have him/her show you
how to administer injectable fluids at home.
Make sure your cat eats and drinks normally. The best way to
prevent dehydration is to have your pet examined and treated
early if an illness occurs. For sick pets, preventing
dehydration may be difficult but if promptly treated, can
result in recovery.
Information In-depth
Dehydration can be caused by numerous illnesses or
abnormalities and can be divided into two main categories:
reduced fluid intake or increased fluid losses.
Reduced Fluid Intake
The body relies on a steady intake of fluid to maintain
hydration. When the ingestion does not meet the body demands,
dehydration occurs. If your pet is not eating or drinking
adequately because of disease or illness, dehydration is
likely to occur. Reduced fluid intake can also occur if there
is either accidental or deliberate deprivation of food or
water. If you leave your pet unattended for several days and
he spills his water bowl, he may be without water for several
days.
Increased Fluid Losses
In some diseases or illnesses, your pet may be able to consume
enough fluid to meet body demands. The most common cause of
this is vomiting and diarrhea or kidney disease. With vomiting
and diarrhea, excess fluids are lost. In kidney disease, the
kidneys are unable to conserve fluids and they excrete excess
fluid in the urine. Other causes of increased fluid losses
include fever, large wounds or burns that ooze fluid or severe
prolonged drooling.
Veterinary Care In-depth
How To Detect Dehydration
There is no single test that can accurately determine the
presence or severity of dehydration. The diagnosis is
generally based on history, physical examination findings and
laboratory tests.
The recent history is very important and can determine if
dehydration is possible and may help determine the underlying
cause. Be prepared to answer questions about:
Your pet’s eating and drinking habits
The presence of vomiting or diarrhea
Whether your pet is urinating more frequently
The presence of excessive drooling
How long the signs have been present
The severity of dehydration is listed as a percentage. This
percentage indicates the amount of fluid the body is lacking.
The maximum amount of dehydration that can be present in a
live animal is 15 percent. Any dehydration beyond that is
incompatible with life.
Care must be taken on interpreting these results in obese or
very thin patients. In obese pets, underestimating the
severity of dehydration can occur easily because the skin
returns to normal due to excessive skin fat. In emaciated or
extremely thin pets, the skin is not as elastic as a normal
pet so the degree of dehydration can be overestimated.
If the pet is less than 5 percent dehydrated, the skin will
immediately return to normal. This mild dehydration is rarely
detected on physical examination. Pets that are 5 percent
dehydrated have a subtle loss of skin elasticity. The skin
will return to normal but does so a little slower than a
normal pet.
Pets with 6 to 9 percent dehydration have a noticeable delay
in the skin returning to normal. The eyes may also appear
sunken and the gums dry.
Pets with 10 to 12 percent dehydration have skin that does not
return to normal position. It will stay in the tented position
until it is physically returned to the normal position. The
eyes are significantly sunken, the heart rate is elevated and
the pulses are weak.
Pets with 12 to 15 percent dehydration are in a life
threatening situation. The pet is typically collapsed,
severely depressed and in shock. Death is imminent if
aggressive and immediate treatment is not provided.
In addition to physical exam findings, lab tests are needed to
determine the presence and severity of dehydration.
A packed cell volume (PCV) and total protein test are
the most important tests. The packed cell volume is the
percentage of red blood cells currently in circulation.
Normal PCV ranges from 35 to 50 percent. In dehydration,
the fluid in the blood is inadequate and the blood becomes
more concentrated. This results in an increase in the PCV.
The total protein is the amount of large protein
molecules in the blood. As with red blood cells, in
dehydration, the concentration of the protein increases
due to a lack of fluid. In a dehydrated animal, both the
PCV and total protein are elevated.
A urinalysis can also help reveal dehydration and may
even help determine an underlying cause. In dehydration,
the concentration of the urine is higher than normal. If a
known dehydrated animal has dilute urine, kidney disease
is the suspected underlying cause of the dehydration.
Complete blood counts and biochemistry profiles can help
determine the overall health of the animal as well as
determine possible underlying causes for dehydration.
Unfortunately, these blood tests do not always diagnose
dehydration and can be normal even in a severely
dehydrated animal.
Treatment
The treatment for dehydration is to rehydrate with fluids.
Since the animal is unable to meet the fluid demands by
consuming sufficient food or water, injectable fluids are
used. The fluids may be given subcutaneously or intravenously.
Intravenous (IV) fluids are preferred since the rehydration is
hastened and can be more appropriately monitored.
Once your pet is diagnosed with dehydration, the amount of
fluid needed must be determined. The volume of fluid that
needs to be replaced is based on the percentage of dehydration
and the animal's body weight. A rough calculation can be made
based on one of the following formulas:
The number of liters of fluid required is equal to
percentage of dehydration multiplied body weight in
kilograms.
The number of milliliters of fluid required is equal to
500 multiplied by the percentage of dehydration multiplied
by the body weight in pounds.
In addition to rehydrating, fluids are also needed to
maintain hydration and meet ongoing fluid needs if the
underlying cause of the dehydration has either not been found
or has not been treated.
There are multiple different types of injectable fluids. The
type of fluid used in based on the concentrations of sodium,
chloride and potassium as well as any other patient needs.
Follow-up
After rehydration, the underlying cause of the dehydration
must be addressed. Additional testing as well as examinations
may be required to find the underlying cause.
Make sure your pet eats and drinks normally. If dehydration is
suspected, prompt veterinary assistance is essential to
prevent further dehydration.
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