Page 289 - Problem-Based Feline Medicine

16 – THE CAT WITH ACUTE DEPRESSION, ANOREXIA OR DEHYDRATION 281

Polydipsia, page 231). Dehydrated animals with Monitor for changes in respiratory pattern and
such a condition will appear to be in renal failure auscultate lungs frequently for evidence of pul-
because of concurrent azotemia and poorly concen- monary edema. Observe extremities and inter-
trated urine (SG < 1.035). mandibular space for subcutaneous edema.
● Cats with hypovolemia from hypoadrenocorticism ● Normal saline, lactated Ringer’s or other balanced
may also present with pre-renal azotemia, hyper- electrolyte solutions.
phosphatemia and poorly concentrated urine. – Rehydration. The goal of initial fluid therapy is
to correct dehydration and achieve 3–5% vol-
Post-renal azotemia. The conditions will result in
ume expansion. Replace fluid deficits over 4–6
azotemia, hyperkalemia and reduced urination.
hours. An initial fluid bolus may be given in an
● Urethral obstruction. A painful turgid bladder is
effort to overcome renal arteriolar vasoconstric-
palpable. Rarely the obstruction has spontaneously
tion. Use 10 ml/kg over 10 minutes in cats with
resolved by the time the cat is presented for exami-
anuria or rapidly progressive oliguria, and 7–10
nation. In the latter case, diagnosis is established by
ml/kg/h for 4–6 hours if there is increased
history, preputial crystal deposits, urinalysis and
concern for pulmonary edema or oliguria is less
azotemia. Note that prolonged urethral obstruction
severe.
may rarely lead to acute renal failure.
● Ruptured bladder. The bladder is not palpable or, The goal of fluid therapy after rehydration is to main-
rarely, is palpable but small, and abdominal fluid is tain 3–5% volume expansion above normal hydra-
present. Creatinine or potassium concentrations tion. More aggressive fluid therapy will not “flush out”
higher in the abdominal fluid than that of serum are or “open up” the kidneys, and overzealous treatment
strongly suggestive of uroperitoneum. A ruptured will result in pulmonary edema. Fluid rate must be
bladder may be confirmed by a positive contrast adjusted based on body weight, central venous pres-
cystogram. See page 464, The Cat With Abdominal sure, PCV and total protein levels and urine output.
Distention or Abdominal Fluid. ● In cats with anuria or oliguria, place a urinary
catheter and attach to a closed collection bag.
Always palpate the bladder whenever checking
Treatment
urine production because the catheter may kink.
Remove or correct the primary cause. Avoid any The urine should be cultured periodically to
nephrotoxic drugs. monitor for urinary tract infection.
● In cats with polyuria, while a urinary catheter may
Administer intravenous fluid therapy.
be used, frequent palpation of the bladder and meas-
● Weigh the cat prior to fluid therapy and monitor
urement of voided urine by weighing the litter pan is
weight throughout treatment. Weight is one of the
usually adequate to estimate urine production.
most important markers of hydration status. Daily
weight loss of 0.5–1% is expected in anorexic Monitor electrolytes and acid–base status (initially
animals, and this should be taken into account three times daily) and adjust fluids accordingly.
when judging hydration based on weight. ● Hyperkalemia is a potentially life-threatening
● Establish a jugular catheter if possible. This will complication of acute renal failure. Signs of signif-
facilitate fluid therapy, repetitive blood sampling icant hyperkalemia include bradycardia and weak-
and measurement of central venous pressure. ness, which may progress to shock and a moribund
– If direct measurement of central venous pressure state. ECG findings include loss of P waves, spiked
is not possible, observe the jugular veins. T waves, and shortened Q–T interval.
Progressive distention of these veins and/or ● Mild hyperkalemia (above reference range to 6.5
increase in the jugular pulse indicates rising cen- mEq/L) may not require immediate treatment. If no
tral venous pressure. The medial saphenous clinical signs are present, one or more of the fol-
veins may also be observed while the hind legs lowing treatments will usually suffice: reducing
are raised and lowered. Decreased emptying potassium concentration in the fluids, changing flu-
and increased refilling of the medial saphe- ids to a more alkalinizing fluid, adding 5% dextrose
nous veins indicates volume expansion. to the fluids, and furosemide (see below).