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When treated promptly, oral rehydration
solutions generally can rehydrate and restore the chemical balance. However,
when severely dehydrated, about 8 percent or more, they need intravenous
fluid therapy from a veterinarian. To help make that judgment call, use
the chart below of visual signs of dehydration.
Assessment of Hydration: Skin turgor
(elasticity), known as the skin pinch test, is informative after three
to five percent dehydration, but varies with the amount of subcutaneous
fat present. Mucous membrane refill and moisture can be helpful, but are
somewhat subjective.
Total body water is approximately
60% of body weight, less in old or obese animals and up to 80% in young
animals
| DEHYDRATION |
ASSESSING HYDRATION
Chart/excerpts
from Assessing hydration by J.Tyler, DVM, MPVM, PhD
Dehydration
of less than 6% of body weight cannot be reliably detected by physical
examination. When dehydration exceeds 12% of body weight, it is generally
fatal. Clinical signs that suggest dehydration include prolonged
skin tenting of the upper eyelid or skin over the neck, sunken eyes, dry
or tacky mucus membranes and generalized depression.
DEMEANOR
|
SKIN
TENTING |
| 0
- 6 % |
Normal
to mildly depressed, decreased urine output. |
-
|
| 6
- 8 % |
+
sunken eyes, tight skin, depression but still standing, dry mouth and nose,
further reduction in urine output. |
+/-
|
| 8
-10 % |
Signs
listed above have worsened, legs and ears are cold, unable to stand. Comatose.
++
sunken eyes. |
2-5
seconds
|
| 10
-12 % |
Shock.
Comatose. +++ sunken eyes |
5-10
seconds |
| >
12% |
Comatos.
Dead. ++++ sunken eyes. |
>10
seconds |
NOTE: fat animals
appear less dehydrated than they truly are, and emaciated animals appear
more dehydrated than they truly are. Obesity results in tight skin which
will not "tent" even when the patient is dehydrated. In addition, the excessive
subcutaneous fat in obese animals results in more skin "pliability." The
converse is true with thin animals.
Fluids may be administered
SQ or IV to any animal with >5% dehydration.
The amount of electrolyte solution
needed each day to correct dehydration is calculated by multiplying
the weight by the percentage of dehydration plus the daily maintenance
(36 ml/lb/day). To maintain hydration = 10% of their body weight each day.
Fluids may be given full bore to
a total volume of 80 ml/kg to any animal that has not had any type of cardiac
manipulation if it is in shock.
The
subcutaneous (SQ, SC) route: SQ
fluids are good for maintenance or mild dehydration.
| Advantages: |
Disadvantages: |
|
Easy to do, you can inject fluids at
any rate, the absorption is slow, and multiple sites are available.
|
Fluids used must be isotonic,
sterile, and non-irritating.
The SQ route is not good if there is
an immediate need (shock).
SQ fluids may not be absorbed if peripheral
perfusion is poor (moderate-severe dehydration).
They are also not indicated if SQ edema
is present.
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Update
May 21, 2002
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