Page 671 - Fluid, Electrolyte, and Acid-Base Disorders in Small Animal Practice

658 SPECIAL THERAPY

transfusion requirements were significantly reduced in renal function related to the older high MW HES should
the group receiving HES 130/0.4. 89 not be extrapolated to the new low MW products. 19,177
In veterinary medicine, administration of hetastarch In people, there is growing evidence that there is a dose-
670/0.75 as compared with 0.9%NaCl has been shown related association between the use of slowly degradable
to affect canine platelet function both in vitro 178 and in hydroxyethyl starch solutions and acute kidney injury in
vivo 148 in clinically healthy dogs. A single dose of HES certain subsets of patients, such as in sepsis. 29,141 Glomer-
670/0.75 at 20 mL/kg IV causes platelet dysfunction ular filtration of a high concentration of small colloid
in dogs for at least 5 hours after injection. The clinical molecules is postulated to cause obstruction of the renal
impact of platelet dysfunction induced by HES solutions tubules or osmotic nephrosis. 59,96 Another concern in
in veterinary medicine remains to be established but it is patients with oliguric or anuric renal failure is that the
reasonable to assume that it could be of clinical signifi- kidneys are the major route of excretion for all artificial
cance. Assessing platelet function by performing a buccal colloids; a situation analogous to the pharmacokinetics
mucosal bleeding time (or other platelet function analysis of mannitol. There is no other rapid excretion route for
if available) following colloid infusion would seem pru- colloids, so animals with renal failure and reduced glomer-
dent in select at-risk patients. ular filtration rate will be at much greater risk of volume
It seems prudent to supplement clotting factors in overload. Although published evidence is lacking in veter-
animals at risk by use of fresh frozen plasma. In addition, inary medicine, it is prudent to limit or avoid artificial col-
desmopressin has been shown to increase factor VIII:C loid therapy in patients with documented renal failure and
activity after hydroxyethyl starch infusion and should be in those at high risk of renal tubular injury/renal failure. If
considered as adjunctive therapy along with fresh frozen use of colloids is deemed necessary in these patients, urine
41
plasma administration. outputandrenalfunctionshouldbemonitoredcloselyand
The observation that colloids impair the action of the dose of colloid (both total cumulative and duration)
endothelial adhesion molecules also raises the possibility should be minimized.
that colloids may reduce neutrophil adhesion in sepsis 37
and explain the higher neutrophil counts observed after ANAPHYLAXIS
dextran 70 infusion in endotoxic shock. 105 Anaphylactic or anaphylactoid reactions have been
reported in people following the administration of
INTRAVASCULAR VOLUME dextrans, hydroxyethyl starches, and gelatins, 125 but
OVERLOAD the incidence of serious complications is extremely

Because colloids are retained within the vascular system to low. 126 Hydroxyethyl starch was associated with pruritus
a greater extent than are crystalloids, there is a greater in up to 33% of patients treated with long-term
likelihood of volume overload with injudicious adminis- infusions. 66 Deposits of hydroxyethyl starch in cutaneous
tration of colloids. Most clinicians are more familiar with nerves 101 and histiocytic skin infiltrates 43 were thought
crystalloid than with colloid infusion rates, and a helpful to be responsible. Interestingly, pruritus also has been
method to ensure a safe colloid infusion rate is to estimate reported after infusion of lactated Ringers solution. 24
the equivalent crystalloid infusion rate. Approximately Several studies have raised concerns about the potential
20% to 25% of crystalloid remains within the intravascular effects of plasma substitutes on reticuloendothelial func-
space 1 hour after infusion compared with 100% of the tion. 140 Decreased concentrations of the opsonic plasma
volume of infused colloid. Therefore multiplying the col- factor, fibronectin, have been reported with use of
loid infusion rate by four allows one to conceptualize the hydroxyethyl starch 165 and gelatins. 26
volume expansion effects of the colloid in terms of an
equivalent crystalloid volume: 20 mL/kg/hr of colloid LABORATORY TESTS AND
is equivalent to 80 mL/kg/hr of crystalloid. Animals INTERPRETATION, CLINICAL
with heart, lung, or brain disease or oliguria/anuria
should be closely monitored during colloid administra- EVALUATION, AND
tion, ideally by direct monitoring of central venous pres- MONITORING
sure. Cats are more likely to develop volume overload
than dogs. This is due in part to their smaller blood vol- Refractometry does not accurately reflect the concentra-
ume as a percentage of body weight, but also to inadver- tion or the osmotic effect of synthetic colloids. 30 The
tently administering the canine dose to a cat. older forms of hydroxyethyl starch and dextran 70 avail-
able in the United States both yield refractometric total
EFFECTS ON THE KIDNEY solids (RTS) readings of 4.5 g/dL. As plasma volume is
Thelowmolecular weightdextranssuchasdextran40have replaced by artificial colloid, the measured RTS should
been reported to cause acute renal failure. 59,96 Renal dys- approach that of the artificial colloid. Theoretically,
function has also been associated with HES solutions administering artificial colloid to an animal with an initial
although recent reports suggest that concerns regarding RTS concentration greater than 4.5 g/dL will reduce the