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A 70-year-old man with multiple myeloma presents for emergency surgery. His serum calcium is 14 mg/dL. Which of the following treatments will be MOST effective at acutely decreasing the serum calcium level?
A. Hydrochlorothiazide X
B. Isotonic saline ✔
C. Zoledronic acid X
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Calcium is essential for many functions, including cellular signaling, neuromuscular junction activity, and blood coagulation. It is also a vital component of the skeletal system. Severe hypercalcemia (>14 mg/dL) can result from multiple disease processes, but is most commonly related to cancer (eg, multiple myeloma). Other causes include vitamin D intoxication, increased calcium absorption through the gastrointestinal tract, renal insufficiency, hyperparathyroidism, and hyperthyroidism. Patients with severe hypercalcemia may experience symptoms such as nausea, anorexia, constipation, lethargy, and confusion. Hypercalcemia can also result in pancreatitis and renal calculi. If hypercalcemia is longstanding, calcifications can form in the heart, brain, and vasculature.
Patients with significant hypercalcemia typically present with severe intravascular volume depletion and require urgent and aggressive therapy, including rehydration with isotonic saline. Intravascular volume replacement increases the glomerular filtration rate and calcium excretion through the urine, as well as diluting the calcium level in the blood. Rehydration is combined with other therapies such as calcitonin, a calcium-lowering hormone that increases calcium excretion and slows bone resorption of calcium. Bisphosphonates may be administered in patients with cancers associated with increased osteoclastic bone resorption. Bisphosphonates such as zoledronic acid reach peak effect about 48 hours after administration and are therefore not the best first-line treatment for life-threatening hypercalcemia. Other treatments that can be used in patients with diseases associated with increased osteoclastic bone resorption include glucocorticoids and mithramycin. However, intravascular fluid administration is the most effective and efficient way to replenish volume and decrease the adverse effects of hypercalcemia. Once the intravascular volume is repleted, diuresis with furosemide can further assist in calcium excretion. Phosphate levels should be monitored, as hypophosphatemia decreases calcium uptake into bone.
Hydrochlorothiazide reduces urinary calcium excretion and may worsen hypercalcemia.
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Date of last update: March 25, 2024
