Page 11 - 2013 AAHA/AAFP Fluid Therapy Guidelines for Dogs and Cats

2013 AAHA/AAFP Fluid Therapy Guidelines for Dogs and Cats

hypertonic saline are 4–5 mL/kg for the dog and 2–4 Patients with body fluid content changes include those with
mL/kg for the cat. Direct effects of hypertonic saline last electrolyte disturbances, blood glucose alterations, anemia, and
30–60 min in the vascular space before osmotic forces polycythemia. Patient assessment will dictate patient fluid content
equilibrate between the intra and extravascular space. Once needs. It is acceptable, and often desirable, to initiate fluid therapy
the patient is stabilized, continue with crystalloid therapy with an isotonic balanced crystalloid solution while awaiting the
to replenish the interstitial fluid loss. electrolyte status of the patient. Tailor definitive fluid therapy as
y In conjunction with synthetic colloids to potentiate the the results of diagnostic tests become available.
effects of the hypertonic saline. 28,29
y Do not use hypertonic saline in cases of either Hyperkalemia
hypernatremia or severe dehydration. Suspect hyperkalemia in cases of obvious urinary obstruction,
uroabdomen, acute kidney injury, diabetic ketoacidosis (DKA), or
Treating hypovolemia due to blood loss changes on an electrocardiogram. If life-threatening hyperkalemia
The decision of when to use blood products instead of balanced is either suspected or present (K  6 mmol/L), begin fluid therapy
electrolyte solutions is based on the severity of estimated blood immediately along with medical therapy for hyperkalemia. 35
loss. Use of blood products is addressed elsewhere. 32,33 If blood There are several benefits associated with administering
products are not deemed necessary, note that patients with low K-containing balanced electrolyte solutions pending labora-
vascular volume (due to either vasodilation or hemorrhage) will tory test results. Volume expansion associated with the fluid
benefit more from the use of colloids than crystalloids. Following administration results in hemodilution and lowering of serum
15 mL/kg of hemorrhage, even 75 mL/kg of crystalloid will not K concentration. The relief of any urinary obstruction results in
return blood volume to prehemorrhage levels because crystalloids kaliuresis that offsets the effect of the administered K. The relative
are highly redistributed. Large volumes may be needed to achieve alkalinizing effect of the balanced solution promotes the exchange
blood volume restoration goals, and large volumes may be det- of K with hydrogen ions as the pH increases toward normal.
rimental to patients with normal whole body fluid volume but Most K-containing balanced electrolyte solutions contain
decreased vascular volume resulting from acute blood loss. 34 lower K concentrations than those typically seen in cats with ure-
thral obstruction, so the use of such solutions does not affect blood
Hypervolemia K in those cats. LRS contains 4 mmol/L, which is typically much
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Hypervolemia can be due to heart failure, renal failure, and/or lower than the serum K levels in cats with urethral obstruction.
iatrogenic fluid overload. Hypertension is not an indicator of
hypervolemia. Treatment is directed at correcting underlying Hypokalemia
disease (e.g., chronic renal disease, heart disease), decreasing or Charts are available in many texts to aid in K supplementation of flu-
stopping fluid administration, and (possibly) use of diuretics. ids and determination of administration rate. It is essential to mix
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Consider using hypotonic 0.45% sodium chloride as maintenance added KCl thoroughly in the IV bag as inadvertent K overdoses can
fluid therapy in patients susceptible to volume overload (such as occur and are often fatal. Do not exceed an IV administration rate
those with heart disease) due to the decreased Na load. of 0.5 mmol/kg/hr of K. If hypophosphatemia exists along with
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hypokalemia (e.g., DKA), use potassium phosphate instead of KCl.
Hyperthermia
Increased body temperature can rapidly lead to dehydration. Hypernatremia
Treatment includes administering IV replacement fluids while Hypernatremia may be common, yet mild and clinically silent.Causes
monitoring for overhydration. Subcutaneous fluids are not ade- of hypernatremia include loss of free water (e.g., through water depri-
quate to treat hyperthermia. vation), and/or iatrogenically (through the long-term use [ 24 hr]
of replacement crystalloids). Another cause of hypernatremia is salt
Changes in Fluid Content toxicity (through oral ingestion of high salt content materials).
Provide for ongoing losses and (in hypotensive patients) vol-
ume deficits with a replacement fluid having a Na concentration
Examples of Common Disorders Causing close to that of the patient’s serum (e.g., 0.9% saline). Once volume
Changes in Fluid Content
needs have been met, replace the free water deficit with a hypotonic
Diabetes solution (e.g., D5W). Additionally, for anorexic patients, provide
Renal disease maintenance fluid needs with an isotonic balanced electrolyte
Urinary obstruction solution. The cause and duration of clinical hypernatremia will
dictate the rate at which Na levels can be reduced without causing

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