As hypocalcemia is most commonly caused by an underlying condition, treating that condition often resolves the hypocalcemia. This includes correction of magnesium or vitamin D levels with supplementation, correction of nutritional status, correction of acid-base disorder, and treatment of underlying liver or kidney disease.
Patients with severely acute or symptomatic hypocalcemia require emergent treatment to raise calcium levels. Acute drop to below 7.5 mg/dL should be treated, with or without symptoms. Initially, 1-2 g of IV calcium gluconate in dextrose should be infused over 10-20 minutes. Calcium chloride can also be used, however calcium gluconate is preferred because it is less likely to cause tissue necrosis if extravasated. This initial bolus must be followed by a slow infusion of 10% calcium in normal saline or dextrose.
Calcium has a direct effect on cardiac membrane potential and excitability, acting to stabilize the cardiac membrane. This effect can be cardioprotective in cases of impaired neuromuscular transmission and alterations in membrane potential, such as hyperkalemia. On the other side, an excess of calcium can also cause cardiac dysfunction. For this reason, IV calcium must be given slowly due to the risk of serious cardiac dysfunction and arrest with more rapid infusion.
Mild or chronic hypocalcemia is defined as a total serum corrected concentration of 7.5-8.0 mg/dL, or an ionized calcium level above 3.0mg/dL, with little to no symptoms. In these cases, oral calcium repletion is preferred. Initially, 1500-2000 mg of elemental calcium given as calcium carbonate or calcium citrate is given daily.
Calcium citrate is a more expensive supplement than calcium carbonate, but it is better tolerated by patients when taken on an empty stomach. Both are equally efficacious as oral medications.
Vitamin D is often needed in conjunction with calcium supplementation. Correction of vitamin D deficiency will correct hypocalcemia if it is the sole underlying cause. Treatment consists of 50,000 international units of ergocalciferol (vitamin D2) or calcitriol (vitamin D3) given once per week for six to eight weeks. In the case of impaired vitamin D metabolism (renal or hepatic dysfunction), calcitriol must be used as the body cannot activate the vitamin D precursors itself.
Low serum magnesium concentration should be corrected with a total of 2g of magnesium sulfate, infused as a 10% solution over 10-20 minutes. This bolus should be followed by a 1 g/hr maintenance dose. Repletion should be continued until serum magnesium level is corrected to >0.8 mEq/L. Persistent or chronic hypomagnesemia can be treated with a daily dose of 300-400 mg of oral magnesium.
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