Page 185 - Fluid, Electrolyte, and Acid-Base Disorders in Small Animal Practice

Disorders of Calcium: Hypercalcemia and Hypocalcemia 175

kg of elemental calcium (0.5 to 1.5 mL/kg of 10% cal- indicate cardiotoxicity resulting from the calcium infu-
cium gluconate) over a 10- to 20-minute sion. Not all clinical signs abate immediately after acute
period. 115,179,446,447 The calcium content of different correction of hypocalcemia; some may persist for 30 to
calcium salts varies considerably (Table 6-5). There is 60 minutes. Nervousness, panting, and behavioral
no difference in effectiveness of calcium salts changes may persist despite return of normocalcemia dur-
administered intravenously to correct hypocalcemia when ing this period, perhaps reflecting a lag in equilibration
the dose is based on elemental calcium content. Calcium between cerebrospinal fluid and ECF calcium
gluconate is often the calcium salt of choice because it is concentrations. 179,297,504 Hyperthermia that resulted
nonirritating if the solution is inadvertently injected from increased muscle activity or seizures may also take
perivascularly. In contrast, calcium chloride is extremely time to dissipate.
irritating to tissues but provides more elemental calcium
in each milliliter of solution (see Table 6-5). Subacute Management of Hypocalcemia
The heart rate and electrocardiogram should be mon- The initial bolus injection of elemental calcium can be
itored during acute infusions of calcium salts. Bradycardia expected to decrease signs of hypocalcemia for as little
may signal the onset of cardiotoxicity arising from exces- as 1 hour to as long as 12 hours if the underlying cause
sively rapid infusion of calcium. Sudden elevation of the of hypocalcemia has not been corrected. Vitamin D
ST segment or shortening of the QT–interval also may metabolites should be administered as soon as possible

TABLE 6-5 Treatment of Hypocalcemia

Drug Preparation Calcium Content Dose Comment

Parenteral Calcium*
Calcium gluconate 10% solution 9.3 mg of Ca/mL a. Slow IV to effect Stop if bradycardia or shortened
(0.5-1.5 mL/kg IV) QT–interval occurs
b. 5-15 mg/kg/hr IV Infusion to maintain
normal Ca
c. SQ diluted calcium SQ calcium salts can cause
salts severe skin necrosis/
mineralization; no longer
recommended as safe
Calcium chloride 10% solution 27.2 mg of Ca/mL 5-15 mg/kg/hr IV Only given IV because
extremely caustic
perivascularly
Oral Calcium {
Calcium carbonate Many sizes 40% tablet 25-50 mg/kg/day Most common calcium
supplement
Calcium lactate 325- and 650-mg 13% tablet 25-50 mg/kg/day
tablets
Calcium chloride Powder 27.2% 25-50 mg/kg/day May cause gastric irritation
Calcium gluconate Many sizes 10% 25-50 mg/kg/day
Time for maximal Time for toxicity
Vitamin D effect to occur: effect to resolve:
Vitamin D2 (ergocalciferol) Initial: 4000-6000 5-21 days 1-18 weeks
U/kg/day;
Maintenance:
1000-2000
U/kg once daily
to once weekly
1,25-(OH) 2 D 3 (calcitriol) Initial: 20-30 1-4 days 2-14 days
ng/kg/day for
3-4 days
Maintenance:
5-15 ng/kg/day
*Do not mix calcium solutions with bicarbonate-containing fluids because precipitation may occur.
{
Calculate dose on elemental calcium content. IV, Intravenous; SQ, subcutaneous.