Page 344 - Fluid, Electrolyte, and Acid-Base Disorders in Small Animal Practice

336 FLUID THERAPY

TABLE 14-5 Interpretation of Hematocrit and Total Plasma Protein Concentrations
PCV (%) Total Plasma Proteins (g/dL) Interpretation

Increased Increased Dehydration
Increased Normal or decreased Splenic contraction
Polycythemia
Dehydration with preexisting hypoproteinemia
Normal Increased Normal hydration with hyperproteinemia
Anemia with dehydration
Decreased Increased Anemia with dehydration
Anemia with preexisting hyperproteinemia
Decreased Normal Nonblood loss anemia with normal hydration
Normal Normal Normal hydration
Dehydration with preexisting anemia and hypoproteinemia
Acute hemorrhage
Dehydration with secondary compartment shift
Decreased Decreased Blood loss
Anemia and hypoproteinemia
Overhydration
From Muir WW, DiBartola SP. Fluid therapy. In: Kirk RW, editor. Current veterinary therapy VIII. Philadelphia: WB Saunders, 1983: 34.

solute, are present. Furthermore, previous administration factor. Careful reduction of fluid administration and
of corticosteroids or furosemide can decrease urinary subsequent observation are warranted in such patients.
concentrating ability. After fluid therapy has been
initiated, USG falls into the isosthenuric range if rehydra- WHAT TYPE OF FLUID
tion has been achieved. SHOULD BE GIVEN?

CAN THE PATIENT CONSUME A fluid is said to be balanced if its composition resembles
AN ADEQUATE VOLUME OF that of extracellular fluid (ECF; e.g., lactated Ringer’s solu-
tion, Normosol-R [Abbott Laboratories, Abbott Park, Ill.],
WATER TO SUSTAIN NORMAL Plasma-Lyte 148 [Baxter Healthcare, Deerfield, Ill.]) and
FLUID BALANCE? unbalanced if it does not (e.g., normal saline).
Fluid preparations may be further classified as crystalloids
Hospitalized patients that have been volume resuscitated orcolloids.Crystalloidsaresolutionscontainingelectrolyte
and rehydrated may not have recovered to the extent that and nonelectrolyte solutes capable of entering all body fluid
appetite and ability to consume water have returned to compartments (e.g., 5% dextrose, 0.9% saline, lactated
normal. Such patients require administration of adequate Ringer’s solution). Crystalloids exert their effects primarily
amounts of fluid to meet their needs. The needs of par- on the interstitial and intracellular compartments. Colloids
tially or completely anorexic hospitalized dogs and cats are large-molecular-weight substances that are restricted
are not well understood. Most predictions about mainte- to the plasma compartment in patients with an uncompro-
nance fluid requirements are extrapolated from studies of mised intact endothelium and include plasma, dextrans,
normal nonanorexic animals. Absorption of nutrients hydroxyethyl starch (hetastarch), and hemoglobin-based
into the bloodstream and their subsequent metabolism oxygen-carrying (HBOC) fluids. Colloids exert their
produces solutes that must be excreted in urine. Sensible primary effect on the intravascular compartment.
fluid losses and urine production are decreased during Some types of colloids may be used in patients with
fasting in normal animals because less solute requires shock and in those with severe hypoalbuminemia (i.e.,
excretion. Thus the maintenance fluid requirements of albumin <1.5 g/dL). A major limitation to the use of
partially or completely anorexic patients are difficult to plasma as a colloid is the rapid disappearance of albumin
predict. Typically fluids are administered to veterinary from the vascular space. Dextran 70 is a polymer of glu-
patients in volumes predicated on the needs of animals cose that has an average molecular weight of 70,000. Its
that are not anorexic. Careful observation of urine pro- use in humans has been associated with coagulopathies.
duction in such patients is warranted. If the patient is Hetastarch has an average molecular weight of
expected to have normal urinary concentrating ability 480,000. In humans, coagulopathies also have been
and is urinating large volumes of dilute urine frequently, associated with the use of hetastarch but typically only
excessive fluid administration may be a contributing when standard dosage recommendations have been