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Hypocalcemia

SX: muscle cramp; & tetany, paresthesia, confusion, convulsion, stridor & drypsnea, diplopia, abd.cramps, urin. frequency, Chvostek's sign (1-2 contractions of the facial muscles in response to percussion at the top of the cheek) & Trousseau's sign (carpal muscular spasm on pressure over brachial arteries x 3 min with BP pressure cuff ).  EKG prolonged QT interval.

RX:
Acute management for symptomatic hypocalcemia should be on an emergency basis with
2 g calcium gluconate (180 mg elemental calcium or 20 ml 10% calcium gluconate)  diluted in 150 ml D5W IV infusion over 10 minutes, followed by infusion of 6 g calcium gluconate in 500 ml D5W over 4-6 hours (10 ml 10% calcium gluconate = 1 g).

Serum calcium should be measured q4-6h. The infusion rate should be adjusted to avoid recurrent symptomatic hypocalcemia and to maintain the serum calcium level at between 8 and 9 mg/dl. The underlying cause should be treated or long-term therapy started, and the IV infusion then should be gradually tapered.

[ CaCl2 10 ml = 272 mg = 13.6 meq Ca++)]

Later on, PO Oscal 500 mg tab 2-4 tab tid as indicated.

Hypomagnesemia, if present, must be treated to correct hypocalcemia. In patients taking digoxin, the ECG should be monitored as hypocalcemia potentiates digitalis toxicity. Calcium and bicarbonate are not compatible IV admixtures.

Long-term management of hypoparathyroidism and pseudohypoparathyroidism

The objective is to maintain serum calcium levels slightly below the normal range (8-9 mg/dl), which usually prevents manifestations of hypocalcemia and minimizes hypercalciuria. While the dose of vitamin D is being titrated, serum calcium should be measured twice weekly. When a maintenance dose is achieved, serum and 24-hour urinary calcium levels should be monitored every 3-6 months, because unexpected fluctuations may occur. If urine calcium exceeds 250 mg/24 hours, the dose of vitamin D should be reduced. If hypercalciuria develops at serum calcium levels of less than 8.5 mg/dl, hydrochlorothiazide (50 mg PO qd) can be used to reduce urinary calcium excretion.

  1. Oral calcium supplements.
    Calcium carbonate (Os-Cal, 250 or 500 mg elemental calcium per tablet; Tums Extra-Strength, 400 mg elemental calcium per 5 ml; or various generic formulations) is the least expensive compound.
    The usual dosage is 1-2 g elemental calcium PO tid.
  2. Vitamin D. Dietary deficiency can be corrected by 400-1000 IU/day, but treatment of other hypocalcemic disorders requires much larger doses of vitamin D or use of an active metabolite.
    In patients with severe hyperphosphatemia, serum phosphorus should be lowered to less than 6.5 mg/dl with oral phosphate binders before vitamin D is started.
    Calcitriol (Rocaltrol, 0.25 or 0.5 mug per capsule)     has a rapid onset of action. The initial dose is 0.25 mug PO qd, and most patients are maintained on 0.5-2.0 mug PO qd. The dose can be increased at 2- to 4-week intervals. Calcitriol is much more expensive than vitamin D, but its lower risk of toxicity makes it the best choice for most patients.
    Vitamin D (50,000 IU or 1.25 mg per capsule)     requires weeks to achieve full effect. The initial dose is 50,000 IU PO qd, and usual maintenance doses are 25,000-100,000 IU PO qd. The dose can be increased at 4- to 6-week intervals.

Diff. Diagnosis of Hypocalcemia:

Ref:
Washington Manual of Medical Therapeutics, 29th ed., Copyright © 1998

     

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