Page 955 - Small Animal Internal Medicine, 6th Edition

CHAPTER 53 Electrolyte Imbalances 927

cat administered once weekly after a strict 12-hour fast,
BOX 53.6 immediately followed by 6 mL of water taken orally and
VetBooks.ir Nonspecific Therapy for Control of Hypercalcemia placement of butter on the nose to promote salivation and
swallowing. The cat should not be fed for 2 hours or longer
after administration of alendronate. Food interferes with
Acute Therapy
1. Correct fluid deficits absorption of the medication, and alendronate can cause
2. Physiologic saline diuresis, 60-180 mg/kg/day IV esophageal erosions. Serum ionized calcium concentration
3. Furosemide, 1-2 mg/kg IV, PO q6-12h should be measured initially 2 to 3 weeks after treatment is
4. Once diagnosis has been established: prednisone, begun and the blood sample obtained just before the next
1-2 mg/kg q12h PO or dexamethasone 0.1-0.2 mg/ treatment is given, to assess efficacy and to monitor for hypo-
kg IV q12h calcemia. Increasing the dose to 20 mg once a week should
Additional Therapy if Above Fails be considered if minimal improvement in hypercalcemia is
1. Calcitonin-salmon, 4-6 IU/kg SC q8-12h noted after 6 to 8 weeks of treatment.
2. Pamidronate, 1-2 mg/kg in 150 mL of 0.9% NaCl IV If prolonged supportive therapy is required (e.g., in
over 2-4 hours an animal with nontreatable malignancy), furosemide,
3. Peritoneal dialysis, hemodialysis corticosteroids, and a low-calcium diet (consult with a
board-certified veterinary nutritionist for current options)
Long-Term Therapy can be used to help control the hypercalcemia. Non–calcium-
1. Furosemide (see above) containing intestinal phosphorus binders (e.g., aluminum
2. Prednisone (see above) hydroxide) should be administered if hyperphosphatemia
3. Low-calcium-containing diet is present. Oral or IV administration of bisphosphonates, as
4. Intestinal phosphate binders if hyperphosphatemia needed to control hypercalcemia, may also be considered.
present (see Chapter 41)
5. Bisphosphonates (pamidronate [see previous];
etidronate, 5-15 mg/kg once to twice daily PO) HYPOCALCEMIA
IV, Intravenous; IM, intramuscular; PO, by mouth; SC, Etiology
subcutaneous.
Hypocalcemia is present if the serum total calcium concen-
include anorexia and vomiting. Although the onset of action tration is less than 9 mg/dL in adult dogs and less than 8 mg/
of calcitonin may be rapid, its effect may be short-lived dL in adult cats, or if the serum ionized calcium concentra-
(hours), and resistance often develops within a few days, tion is less than 1.0 mmol/L, although reference ranges may
presumably because of downregulation of calcitonin recep- vary between laboratories. Hypocalcemia develops with
tors. The transitory effect of calcitonin and its expense have increased demands of reproduction (e.g., preparturient or
limited its usefulness for treating hypercalcemia. puerperal tetany), decreased calcium resorption from bone
Bisphosphonates inhibit bone resorption by decreasing or kidney (e.g., primary hypoparathyroidism), decreased
osteoclast activity and function and inducing osteoclast calcium absorption from the gastrointestinal tract (e.g., mal-
apoptosis. Pamidronate has been used to treat dogs and cats assimilation syndromes), or increased precipitation-chelation
with a variety of disorders causing hypercalcemia, including of serum calcium (e.g., ethylene glycol toxicity, acute pancre-
cholecalciferol rodenticide toxicosis, hypercalcemia caused atitis). The acute onset of hyperphosphatemia can also cause
by lymphoma, myeloma, osteosarcoma, primary hyperpara- hypocalcemia. The most common causes of hypocalcemia in
thyroidism, and nocardiosis. The IV administration of pami- dogs and cats are hypoalbuminemia, puerperal tetany, acute
dronate has a rapid onset of action and is effective in lowering and chronic kidney disease, malassimilation syndromes,
serum total and ionized calcium concentrations. The only critical illness (e.g., sepsis, systemic inflammatory response
adverse reaction reported with pamidronate is renal toxicity, syndrome [SIRS]), and primary hypoparathyroidism (espe-
which appears to be uncommon. Factors that affect onset of cially after thyroidectomy in hyperthyroid cats; see Table
renal toxicity in humans include type of bisphosphonate 47.3). The serum total calcium concentration is typically
administered, rate of infusion, and hydration status of the decreased in animals with concurrent hypoalbuminemia for
patient. Administration of pamidronate before a definitive reasons discussed in the section on hypercalcemia. Depend-
diagnosis has been obtained should not adversely affect ing on the underlying cause, the serum ionized calcium con-
establishing the cause of the hypercalcemia. centration may or may not be decreased. Serum ionized
The oral bisphosphonate alendronate has been used to calcium should be measured before a diagnosis of hypocal-
treat idiopathic hypercalcemia in cats that have failed to cemia is rendered in an animal, especially if a decreased
respond to changes in diet and oral prednisolone. Alendro- serum albumin concentration is present.
nate is not recommended until the serum calcium concen-
tration exceeds 13 mg/dL. Oral alendronate is not as effective Clinical Features
as injectable. The currently recommended treatment proto- Animals with hypocalcemia range from being asymptomatic
col developed by Dr. Dennis Chew is one 10-mg capsule per to showing severe neuromuscular dysfunction. Serum total