Page 6 - 2013 AAHA/AAFP Fluid Therapy Guidelines for Dogs and Cats

2013 AAHA/AAFP Fluid Therapy Guidelines for Dogs and Cats

provide limited usefulness at low IV infusion rates. It is not pos- Alternatively, fluid made up of equal volumes of replacement solu-
sible to provide sufficient heat via IV fluids at limited infusion tion and D5W supplemented with K (i.e., potassium chloride
rates to either meet or exceed heat losses elsewhere. 1 [KCl], 13–20 mmol/L, which is equivalent to 13–20 mEq/L)
would be ideal for replacing normal ongoing losses because of the
Fluids for Maintenance and Replacement lower Na and higher K concentration. Another option for a main-
Whether administered either during anesthesia or to a sick patient, tenance fluid solution is to use 0.45% sodium chloride with 13–20
fluid therapy often begins with the maintenance rate, which is the mmol/L KCl added. Additional resources regarding fluid therapy
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amount of fluid estimated to maintain normal patient fluid bal- and types of fluids are available on the AAHA and AAFP websites.
ance (Table 3). Urine production constitutes the majority of fluid
loss in healthy patients. Maintenance fluid therapy is indicated Fluids and Anesthesia
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for patients that are not eating or drinking, but do not have vol- One of the most common uses of fluid therapy is for patient
ume depletion, hypotension, or ongoing losses. support during the perianesthetic period. Decisions regarding
Replacement fluids (e.g., LRS) are intended to replace lost body whether to provide fluids during anesthesia and the type and
fluids and electrolytes. Isotonic polyionic replacement crystalloids volume used depend on many factors, including the patient’s
such as LRS may be used as either replacement or as maintenance signalment, physical condition, and the length and type of the
fluids. Using replacement solutions for short-term maintenance procedure. Advantages of providing perianesthetic fluid therapy
fluid therapy typically does not alter electrolyte balance; however, for healthy animals include the following:
electrolyte imbalances can occur in patients with renal disease or y Correction of normal ongoing fluid losses, support of
in those receiving long-term administration of replacement solu- cardiovascular function, and ability to maintain whole
tions for maintenance. body fluid volume during long anesthetic periods
Administering replacement solutions such as LRS for mainte- y Countering of potential negative physiologic effects associated
nance predisposes the patient to hypernatremia and hypokalemia with the anesthetic agents (e.g., hypotension, vasodilation)
because these solutions contain more sodium (Na) and less potas- y Continuous flow of fluids through an IV catheter prevents
sium (K) than the patient normally loses.Well-hydrated patients clot formation in the catheter and allows the veterinary
with normal renal function are typically able to excrete excess team to quickly identify problems with the catheter prior
Na and thus do not develop hypernatremia. Hypokalemia may to needing it in an emergency
develop in patients that receive replacement solutions for mainte- When fluids are provided, continual monitoring of the
nance fluid therapy if they are either anorexic or have vomiting or assessment parameters is essential (Table 1). The primary risk of
diarrhea because the kidneys do not conserve K very well. 4 providing excessive IV fluids in healthy patients is the potential for
If using a replacement crystalloid solution for maintenance vascular overload. Current recommendations are to deliver  10
therapy, monitor serum electrolytes periodically (e.g., q 24 hr). mL/kg/hr to avoid adverse effects associated with hypervolemia,
Maintenance crystalloid solutions are commercially available. particularly in cats (due to their smaller blood volume), and all
patients anticipated to be under general anesthesia for long periods
of time (Table 4). 6–8 In the absence of evidence-based anesthesia
TABLE 1 fluid rates for animals, the authors suggest initially starting at 3
mL/kg/hr in cats and 5 mL/kg/hr in dogs. Preoperative volume
Evaluation and Monitoring Parameters that May loading of normovolemic patients is not recommended.
Be Used for Patients Receiving Fluid Therapy The paradigm of “crystalloid fluids at 10 mL/kg/hr, with
higher volumes for anesthesia-induced hypotension” is not evi-
y Pulse rate and quality y Packed cell volume/total solids dence-based and should be reassessed. Those high fluid rates may
y Capillary refill time y Total protein actually lead to worsened outcomes, including increased body
y Mucous membrane color y Serum lactate weight and lung water; decreased pulmonary function; coagula-
y Respiratory rate and effort y Urine specific gravity tion deficits; reduced gut motility; reduced tissue oxygenation;
y Lung sounds y Blood urea nitrogen increased infection rate; increased body weight; and positive fluid
y Skin turgor y Creatinine balance, with decreases in packed cell volume, total protein con-
y Body weight y Electrolytes centration, and body temperature. 9,10 Note that infusion of 10–30
y Urine output y BP mL/kg/hr LRS to isoflurane-anesthetized dogs did not change
y Mental status y Venous or arterial blood gases either urine production or O2 delivery to tissues. A fluidconsum-
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y Extremity temperature y O saturation
2 ing “third space” has never been reliably shown, and, in humans,
BP, blood pressure. blood volume was unchanged after overnight fasting. 12

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