Page 420 - Fluid, Electrolyte, and Acid-Base Disorders in Small Animal Practice

410 FLUID THERAPY

HYPERGLYCEMIA delivery to tissues because of inadequate circulating vol-
ume, correction of the volume deficit may reverse acidosis
Hyperglycemia typically occurs in diabetic dogs and cats,
without the need for further therapy. Dogs and cats with
and in stressed cats. Hyperglycemia itself may not be dan-
diabetic ketoacidosis rarely require exogenous alkali if
gerous; however, if blood glucose concentration exceeds
fluid therapy and insulin administration are managed
400 mg/dL, it may contribute to a hyperosmolar diuresis
appropriately. In cases in which the underlying condition
with subsequent dehydration. With diabetic animals, it is
is difficult to reverse (e.g., hypoxemia related to airway
ideal if anesthesia can be postponed until blood glucose
pathology, heart failure, pheochromocytoma), it is
concentration can be better regulated. If this is not feasi-
important to manage the acidosis before anesthesia. This
ble, the animal should be treated with insulin and glucose
to stabilize blood glucose concentration between 200 is normally done using sodium bicarbonate, but
and 300 mg/dL. In patients with brain trauma or those Carbicarb and tromethamine may also be used (see
suffering from focal or global brain ischemia during sur- Chapter 10). Sodium bicarbonate usually is available as
gery, hyperglycemia may be detrimental to the neurologic an 8.4% solution with 1 mEq bicarbonate per milliliter
outcome. 36,165,166,191 In animal models, blood glucose and an osmolality of 2000 mOsm/L. In animals that
are hyperosmolar or hypernatremic, it may be advisable
concentrations as low as 150 to 200 mg/dL have been
to dilute bicarbonate to an isosmotic solution to prevent
shown to have negative effects on outcome, but the
further exacerbation of the animal’s condition. An osmo-
threshold for cerebral damage seems to be approximately
200 mg/dL. 115,166 In a study of dogs, dextrose adminis- lality of 300 mOsm/L can be achieved by diluting
1.5 mL of the 8.4% solution in 8.5 mL of sterile water.
tration was associated with greater renal damage after an
ischemic insult than lactated Ringer’s solution (LRS). 128 Sodium bicarbonate also should not be administered
through the same intravenous line as catecholamines
It is thought that increased intracellular glucose
contributes to lactic acidosis in the cell, decreasing the because it inactivates them (Table 17-1). Care should
chance of cell survival. be taken when administering sodium bicarbonate to
patients with respiratory depression because it increases
the production of CO 2 . If the animal is unable to increase
METABOLIC ACIDOSIS its ventilation in response to increased production of
Dogs and cats generally tolerate moderate acidosis CO 2 , there may be little overall change in pH.
reasonably well. However, severe acidosis is likely to lead
to reduced activity of enzyme systems in the body with METABOLIC ALKALOSIS
subsequent alterations in energy production and metab- Conditions that cause metabolic alkalosis may be
olism of drugs. Acidosis also may alter the activity of some associated with a high mortality rate, and 10 of 20 dogs
anesthetic drugs because more of the un-ionized active with primary alkalemia died in one study. 151 Induction of
form of anionic drugs is available at lower pH values. anesthesia in an alkalotic patient may be associated with
In patients with acidosis arising from insufficient oxygen an increased dose requirement because of a decreased

TABLE 17-1 Compatibility of Intravenous Solutions with Other Drugs That Might Be

Administered During Anesthesia
Solution Comments

5% Dextrose The pH of the solution ranges from 3.5 to 6.5, so alkaline solutions may precipitate.
Lactated Ringer’s Slightly acidic and contains calcium. Do not administer with blood products. Sodium bicarbonate may also
react with the calcium and form calcium carbonate.
Acetated polyionic If it contains no calcium, can be used with blood products and sodium bicarbonate.
Sodium chloride 0.9% Usually slightly acidic but is compatible with most intravenous solutions; may cause precipitation if added to
mannitol.
Sodium bicarbonate Alkaline solution—incompatible with dobutamine, dopamine, isoproterenol, norepinephrine, and
epinephrine. May react with calcium in solution (e.g., lactated Ringer’s, acetated Ringer’s, some
polygelatins).
Dextrans Slightly acidic—may degrade acid-labile drugs and may form drug complexes but appear to be compatible
with most intravenous solutions.
Hetastarch May be incompatible with some antibiotics—crystals formed with amikacin, cefamandole, cefoperazone, and
tobramycin.
Polygelatins Some preparations contain calcium, and these should not be used with blood products or sodium
bicarbonate.
Blood and plasma Do not administer through the same line as calcium salts.