Page 567 - Problem-Based Feline Medicine

25 – THE CAT WITH POLYCYTHEMIA 559

pulmonary edema. Use a syringe pump or infu- ● Haemaccel® is a colloid solution available in
sion pump because cats are very sensitive to the Europe and Australasia that is comprised of 3.5%
volume expansion effects of colloids, and manual polygeline, a gelatin-based colloid.
administration increases the risk of adverse effects
To achieve a very rapid increase in intravascular vol-
such as pulmonary edema. Hypothermic cats are
ume using low volumes of infused fluids, colloids and
particularly sensitive to colloids, and administering
hypertonic saline can be combined. Replacement or
hypertonic saline or colloids to cats with undiag-
maintenance crystalloids are administered concurrently
nosed and asymptomatic hypertrophic cardio-
to maintain or replenish interstitial and intracellular
myopathy may precipitate pulmonary edema.
fluid levels, and are administered at 50% of the volume
Colloid solutions include dextran, hydroxyethyl that would be required if they were used alone.
starch (HES) and hemoglobin-based oxygen-carrying Examples of combinations used are:
solutions such as Oxyglobin®. They are contraindi- ● Combine 1.3 ml/kg of 23.4% NaCl with 2.7 ml/kg
cated for use in very dehydrated, oligouric patients of 6% hetastarch, and administer slowly over 10–15
because the possibility of renal damage is increased. minutes. Mixing the solutions together results in a
The fluid attracted intravascularly comes from within 7.5% NaCl solution.
cells, exacerbating intracellular dehydration. ● 20% NaCl at 1.5 ml/kg combined with Dextran 70
● Colloid osmostic pressure (COP) and volume- at 3 ml/kg and administer slowly over 10–15 min-
expanding capacity varies with the colloid as fol- utes. Mixing results in approximately 7% NaCl.
lows:
Plasma can be used as a colloid, but it is best used
● 6% hetastarch has a COP of 30 mmHg, and expands
when there is a specific indication such as pancreatitis
the volume by 1–1.3 ml per ml of colloid infused,
or a coagulation disturbance. It is not the preferred
and stays in the vascular space for 12–48 h.
method of replacing albumin or improving the oncotic
● 10% dextran 40 has a COP of 40 and expands the
pressure, because the volume of plasma required to
volume by 1–1.5 ml per ml of colloid infused, and
measurably increase serum albumin concentration is
stays in the vascular space for 4–8 h.
very large. However, it can be used as a component of
● 6% dextran 70 has a COP of 40 and expands the
fluid therapy to help increase plasma oncotic pressure
volume by 0.8 ml per ml of colloid infused, and
in a hypoproteinemic cat, and to decrease the tendency
stays in the vascular space for 4–8 h.
for loss of intravascular fluid. Plasma can be adminis-
● Dextran is made from high-molecular-weight lin-
tered at 20 ml/kg over 4 h in place of 1/3 of the calcu-
ear glucose polymers produced by bacteria, and is
lated crystalloid fluid volume to be administered.
available as Dextran 40 and 70, but Dextran 40 is
rarely used in veterinary medicine because of its The intravenous route of fluid administration is pre-
association with acute renal failure. The dose rate is ferred for correction of severe dehydration, major elec-
5–10 ml/kg, beginning with the lower dose. trolyte and acid–base imbalances, and shock. While the
● Hydroxyethyl starch is composed primarily of jugular, cephalic, femoral and saphenous veins are
amylopectin, and is a branched polysaccharide available for IV catheter placement, the cephalic vein is
closely resembling glycogen. It is available as the site of choice as the catheter is most readily secured
Hetastarch and Pentastarch. The standard dose rate at that site and less commonly soiled with urine and
is 10–15 ml/kg/day, but administer 2–5 ml/kg ini- feces than in caudal limb sites.
tially and re-evaluate the cat.
Fluid rates administered depend on the requirement of
● Oxyglobin® is used primarily for its oxygen-
the animal.
carrying capacity, but can be used for its colloidal
effect. However it is expensive to use solely for vol- If the cat has insufficient plasma volume to maintain
ume expansion. The COP of Oxyglobin is 37 mmHg, tissue perfusion, intravascular volume must be restored
thus, it has slightly more colloidal pull than rapidly.
Hetastarch, and retains oxygen-carrying capacity ● Inadequate tissue perfusion is indicated by:
for up to 40 h. The dose rate in cats is 1–2 ml/kg/h – Tachycardia and tachypnea, and sometimes
with a total dose of 15 ml/kg. bradycardia.