Page 356 - Fluid, Electrolyte, and Acid-Base Disorders in Small Animal Practice

346 FLUID THERAPY

approximate daily fluid requirements. Daily fluid
requirements of anorexic dogs and cats in a hospital envi-
ronment and the relationship of these fluid requirements
to the daily urinary solute load are areas deserving future
clinical study.
At the Ohio State University Veterinary Teaching
Hospital, the maintenance fluid requirement for dogs
and cats is determined from reference charts that use
the above formulas to calculate accurate daily fluid
requirements based on caloric needs. Although estimates
of 40 to 60 mL/kg/day frequently are used to calculate
maintenance fluid requirements, it is important to recog-
nize that such estimates are only accurate for some veteri-
nary patients. Cats, very small dogs, and very large dogs
are not well served by the use of such estimates, and these
patients likely will benefit from more accurate assessment
of their fluid requirements. Approximately two thirds of
the maintenance requirement represents sensible (i.e.,
easy to measure) losses of fluid (urine output), and one
third represents insensible (i.e., difficult to measure)
losses (primarily fecal and respiratory water loss). Thus
daily maintenance for a 10-kg dog may be 600 mL, with
400 mL representing sensible loss and 200 mL
representing insensible loss.
Some clinicians multiply maintenance fluid
requirements by some factor between 1 and 3 to estimate
a patient’s 24-hour fluid needs. Assuming 60 mL/kg/
day to represent the maintenance rate of fluid administra-
tion, the information in Table 14-9 can be used to quickly
determine the implied hydration deficit and actual rate of
fluid administration using this approach.
In addition to the hydration deficit (replacement
requirement) and maintenance requirement, contempo-
rary (ongoing) losses must be considered. These are not
always easily determined or quantitated in small animals
but can be very important in fluid therapy. An attempt
should be made to estimate ongoing losses, which may
include losses related to vomiting, diarrhea, polyuria,
large wounds or burns, drains, peritoneal or pleural
Figure 14-6 Buretrol device. (From Chew DJ. Parenteral fluid losses, panting, fever, and blood loss. During surgical
therapy. In: Sherding RG, editor. The cat: diseases and clinical procedures, careful attention should be given to the
management. New York: Churchill Livingstone, 1989: 53.) amount of blood lost, drying of exposed tissues, and
effusions removed by suction. Blood lost at surgery
where W is body weight in kilograms. This relationship is should be estimated, and 3 mL of crystalloid solution
plotted in Figure 14-7 so that BER may be determined should be administered for each milliliter of blood lost.
from body weight. Each 4 4-inch gauze sponge, when saturated with
The maintenance energy requirement (MER) is that blood, represents a blood loss of 15 mL. 28 Contempo-
of a moderately active adult animal in a nonthermoneutral rary losses must be estimated and carefully replaced along
environment. The MER in sedentary animals is approxi- with the maintenance volume of fluid. Box 14-1
mately 1.5 to 2.0 BER. summarizes the components of fluid therapy and their
In domestic cats, the relationship of basal heat produc- calculation.
tion to body weight is almost linear because of the small
size and relatively narrow normal range of body weight in FAILURE TO ACHIEVE REHYDRATION
this species. 25 Based on available data, BER in cats may be Repeated assessment of the patient by observation of clin-
estimated as 50 to 60 kcal/kg/day. However, the ques- ical signs and determinations of body weight, urine out-
tion remains whether daily energy requirements put, PCV, TPP, and USG is mandatory in making