Page 956 - Small Animal Internal Medicine, 6th Edition

928 PART VII Metabolic and Electrolyte Disorders

calcium concentrations between 7 and 9 mg/dL are usually
clinically silent; dogs and cats with clinical signs usually have BOX 53.7
VetBooks.ir serum calcium values less than 7 mg/dL (ionized calcium Treatment of Hypocalcemia in Dogs and Cats
<0.8 mmol/L), but severity of hypocalcemia and the pres-
ence of clinical signs are unpredictable and depend on the
magnitude, rapidity of onset, and duration of hypocalcemia. Immediate Treatment of Symptomatic Hypocalcemia
Calcium gluconate 10% solution
The most common clinical signs are directly attribut- Dosage: 0.5-1.5 mL/kg IV slowly to effect
able to a hypocalcemia-induced increase in neuronal excit- Monitor for bradycardia and arrhythmias
ability and include nervousness, behavioral changes, focal Goal: to resolve clinical signs of hypocalcemia
muscle twitching (especially ear and facial muscles), muscle Parenteral Treatment to Prevent Symptomatic
cramping, stiff gait, tetany, and seizures. Seizures are not Hypocalcemia
usually associated with loss of consciousness or urinary
incontinence. Early indicators of hypocalcemia, especially Continuous IV infusion of 10% calcium gluconate
Initial dosage: 60-90 mg elemental calcium/kg/day
in cats, include lethargy, anorexia, intense facial rubbing, 10 mL of 10% calcium gluconate provides 93 mg of
and panting. Exercise, excitement, and stress may induce elemental calcium
or worsen clinical signs. Additional physical examination Administer via syringe pump in separate IV line
findings may include fever, a “splinted” abdomen, cardiac Do not add to fluids containing lactate, acetate,
abnormalities (e.g., weak femoral pulses, bradycardia, tachy- bicarbonate, or phosphates
cardia), and cataracts. Monitor serum ionized or total calcium q8-12h, and
adjust infusion rate accordingly
Diagnosis Goal: to avoid clinical signs of hypocalcemia while
Hypocalcemia should be confirmed before diagnostic tests correcting the cause and/or waiting for oral
are begun to identify the cause, preferably by measuring the calcium and vitamin D therapy to take effect
serum ionized calcium concentration. The list of differential Oral Vitamin D and Calcium Treatment for Hypocalcemia
diagnoses for hypocalcemia is relatively short, and the 1,25-Dihydroxyvitamin D 3 (calcitriol) is preferred because
history, physical examination findings, CBC, serum bio- of its fast onset of action
chemistry panel, urinalysis, and tests for pancreatitis (e.g., Available as 0.25-µg and 0.50-µg capsules
canine pancreatic lipase immunoreactivity [cPLI], abdomi- Initial dosage: 0.02-0.03 µg/kg/day
nal ultrasound) usually provide the clues necessary to Monitor serum ionized or total calcium q12-24h, and
establish the diagnosis (see Table 47.3, p. 765). Primary adjust dosage or frequency of administration
hypoparathyroidism is the most likely diagnosis in the non- accordingly
azotemic, nonreproductive dog or cat with clinical signs of Goal: to avoid clinical signs of hypocalcemia and
hypocalcemia and normal serum magnesium concentration. development of hypercalcemia; target total calcium
The finding of a low or undetectable baseline serum PTH concentration is between 9 and 10 mg/dL
concentration confirms this diagnosis. Hypermagnesemia Oral calcium gluconate, calcium lactate, or calcium
carbonate tablets
and hypomagnesemia can impair the secretion of PTH and Various tablet strengths available, ranging from
PTH actions on its receptor, so measurement of serum mag- 30-500 mg calcium/tablet
nesium (preferably ionized magnesium) is important, espe- Initial dosage: approximately 25-50 mg of Ca/kg
cially in animals with refractory hypocalcemia. q24h, dose often divided
Typically used in conjunction with vitamin D
Treatment Dosage and frequency of administration adjusted on
Therapy should be directed at eradicating the underlying the basis of serum ionized or total calcium
cause of the hypocalcemia. Administration of calcium may concentration
not be indicated if the patient is stable, no clinical signs of
hypocalcemia are noted, and the serum calcium concentra- IV, Intravenous.
tion is stable. Vitamin D, calcium, or both are indicated if
clinical signs of hypocalcemia are present, if the serum total should be stopped briefly. Calcium-rich fluids should be
calcium concentration is less than 7.5 mg/dL, if the serum infused with caution in dogs or cats with hyperphosphate-
ionized calcium concentration is less than 0.8 mmol/L, or if mia because these fluids can increase the probability of min-
hypocalcemia has developed quickly and is progressively eralization of soft tissues, most notably in the kidney.
decreasing. If hypocalcemic tetany is present, calcium should Once signs of hypocalcemic tetany have been controlled
be administered intravenously slowly to effect (Box 53.7). with IV calcium, oral vitamin D, oral calcium, or both may
Calcium gluconate is the preferred agent because it is not be needed to prevent the recurrence of clinical signs. If the
caustic if administered outside of the vein, unlike calcium cause of hypocalcemia is readily reversible and the hypocal-
chloride. Auscultation and electrocardiographic monitoring cemia is anticipated to be short-lived (e.g., weaning puppies
are advisable during calcium administration; if bradycardia from a bitch with puerperal tetany), oral calcium combined
or shortening of the QT interval occurs, the IV infusion with IV calcium gluconate as needed may be all that is