Page 672 - Fluid, Electrolyte, and Acid-Base Disorders in Small Animal Practice

Fluid Therapy with Macromolecular Plasma Volume Expanders 659

measured RTS, whereas administering artificial colloids primary and secondary hemostasis may be affected by col-
to an animal with an initial RTS concentration less than loid administration. For primary hemostasis, platelet
4.5 g/dL should increase the measured RTS toward function defects have been documented in dogs 178 so it
4.5 g/dL. However, in vitro addition of either of these is likely that buccal mucosal bleeding times may also be
colloid preparations (in an amount corresponding to a prolonged. Increases in partial thromboplastin time
22-mL/kg dose in a patient) to a 2.5% solution of human may also be seen, presumably due to colloid-induced
serum albumin (initial RTS concentration, <2.5 g/dL) reductions in factor VIII and direct interference in clot
led to minimal increases in the RTS concentration despite formation. Finally, colloids have been reported to
an increase in measured COP. 30 As more artificial colloid increase plasma viscosity, 22 and hydroxyethyl starch can
was added to the albumin solution, the RTS concentra- produce predictable but potentially misleading results
tion did increase, but the amount of colloid necessary in blood typing and crossmatching. 50
to cause this change was greater than the volume likely
to be used in clinical patients. ACKNOWLEDGMENTS
The in vivo situation is more complicated because of
other effects such as extravasation, excretion of colloid, The authors gratefully acknowledge Dr. Lisa Smart BVSc,
and osmotic fluid shifts into the vascular space after DACVECC for her assistance with the sections on
administration. In the authors’ experience, most patients treatment complications and adverse effects and labora-
with preinfusion RTS concentration of 5 g/dL have a tory tests and interpretation, clinical evaluation, and
decrease in RTS concentration after colloid administra- monitoring.
tion. Conversely, increases in RTS after colloid adminis-
tration seem to be uncommon, regardless of the initial
RTS. The clinician should anticipate the dilutional effect
caused by intravascular volume expansion that occurs REFERENCES
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