Page 404 - Fluid, Electrolyte, and Acid-Base Disorders in Small Animal Practice

394 FLUID THERAPY

hyperlactatemia has been noted in dogs with lymphosar- marketed) compared with crystalloids. 3 Some of the
coma receiving lactated Ringer’s solution. concerns for the use of colloids are coagulopathy, renal
Because of the calcium content of lactated Ringer’s injury and edema.
solution, blood transfusions should not be given through
the same fluid administration set. Lactated Ringer’s solu- Coagulopathy
tion will result in microscopic clot formation in blood A clinical study evaluating the safety and efficacy of
products. 69 hetastarch after a total dosage of between 9 and 59 mL/
Acetated polyionic solutions (Plasma-Lyte 148, kg in dogs with varying problems and associated
Plasma-Lyte A, Baxter Corp, Mississauga, Ontario, hypoalbuminemia reported minor hetastarch-associated
Canada) (Normosol-R, Abbott Laboratories Ltd., changes in coagulation tests that were of little clinical rele-
Montreal, Quebec, Canada) contain acetate as the vance. 77 However, none of these dogs had preexisting
alkalinizing component. Acetate is metabolized in muscle coagulopathies. A potential complication of colloid
cells, and therefore specific organ dysfunction (e.g., kid- administration is hemorrhage, if a preexisting condition
ney disease, liver disease) is not a contraindication for its exists in a patient with a moderate coagulopathy. Hemor-
use. It has been suggested that these solutions not be rhage associated with administration of synthetic colloids
4
administered to animals with diabetic ketoacidosis has been reported in some human patients. A recent vet-
(DKA) because acetate is a ketone precursor and may pro- erinarystudyidentifiedaprolongedplateletclosuretimein
mote ketone production. This concern appears to be the- healthy dogs administered 20 mL/kg of hetastarch (670/
oretical because concurrent treatment for DKA with 0.75).Theconclusionsofthisstudywerethatthepotential
insulin prevents further ketone production. Many platelet dysfunction, in addition to the effects of hemodi-
76
patients with DKA are acidemic, and crystalloid solutions lution, may increase the risk of bleeding.
containing acetate have been my choice for fluid therapy
for several years. Rapid administration of polyionic ace- Renal Injury
tate solutions may precipitate vasodilatation and hypo- Synthetic colloids are eliminated primarily by renal excre-
tension in animals that already are hypovolemic. 65 tion, and caution must be used when administering these
Although this is likely a rare event, with no prospective products as rapid volume expanders to patients with
studies investigating this in veterinary medicine, monitor- oliguria unless oliguria is determined to be caused by
ing blood pressure during administration of acetated hypovolemia or hypotension. These products should
crystalloid solutions is recommended. Hypertonic saline not be administered to patients with anuric renal failure
solutions have been recommended for various conditions or congestive heart failure because of concern about vol-
and have several positive attributes. However, rate of ume overload. Interference with renal function has been
infusion is important, and rapid infusions may result in reported in human patients receiving synthetic colloids,
bronchoconstriction and shallow breathing. 72 and most commonly this observation has been associated
with use of dextran 40. 16 A reduction in the GFR also has
Colloid Solutions been noted in human surgical and trauma patients receiv-
6
Syntheticcolloidsolutionsarerecommendedformanyclin- ing synthetic colloids. A recent Cochrane review, how-
ical situations, and the commonly used synthetic colloid ever, concluded that in surgical and trauma patients
solutions are formulated in 0.9% sodium chloride. The pri- there was no difference with respect to risk of kidney fail-
mary acid-base effect of the colloid solutions on plasma is ure or need for dialysis between patients treated with
acidification. The electrolyte preparations that accompany HES and other fluids, however, it was noted that there
thesemacromolecules(e.g.,0.9%saline)alsohaveanimpor- were too few studies to absolutely conclude association
tant effect on acid-base equilibrium after infusion. 46 of risk. On the other hand, administration of HES to sep-
Considering the frequency of use of these products in tic patients revealed a 55% increased risk of developing
veterinary practice, very little has been published with kidney failure and a 59% increased risk of requiring dialy-
regard to complications after their administration. A very sis. Products with lower molecular weight and degree of
recent review on the use of colloids in humans states that substitution are reported to have better safety profiles;
“crystalloids in general, and albumin in many conditions however, insufficient evidence exists in the literature at
except in patients with closed head injury (SAFE), have this time to support this. 11
been shown to be safer than older starches in critically Where oncotic pressure is normal, caution is warranted
ill patients. They should therefore be considered the gold with colloid administration because a high oncotic pressure
standard for future safety trials”. The review summarizes may result in renal dysfunction. Based on the observation
that synthetic colloids are without superior effect in criti- that renal dysfunction was shown to parallel an increase in
cally ill adults and children but must be considered harm- plasma oncotic pressure, which was sufficient to oppose
ful depending on the cumulative dose administered. This hydraulic filtration pressure within Bowman’s capsule, the
review also comments on the lack of evidence for the concept of hyperoncotic renal failure has been proposed
superiority of 6% HES/0.4 (the most recent colloid in human medicine. 68 This syndrome has been reported