Hypercalcemic crisis

Hypercalcemia of malignancy develops quickly and is associated with anorexia, nausea and vomiting, constipation, polyuria, polydipsia, and nocturia. Hypercalcemic crisis is characterized by acute elevation of serum calcium to greater than 15 mg/dL, acute renal failure, and obtundation. Untreated hypercalcemic crisis can progress to oliguric renal failure, coma, and life-threatening ventricular arrhythmias. 

Hypercalcemic crisis and symptomatic hypercalcemia are medical emergencies requiring immediate treatment. Rehydration with normal saline followed by loop diuretics can be used in patients with normal to moderately impaired renal function. Initiate treatment with calcitonin in patients in whom saline hydration is contraindicated (Table 78-3). 

Hypercalcemia causes central nervous system depression, including coma, and is potentially lethal. Its major causes (other than thiazide therapy) are hyperparathyroidism and cancer with or without bone metastases. Less common causes are hypervitaminosis D, sarcoidosis, thyrotoxicosis, milk-alkali syndrome, adrenal insufficiency, and immobilization. With the possible exception of hypervitaminosis D, these latter disorders seldom require emergency lowering of serum calcium. A number of approaches are used to manage the hypercalcemic crisis. 

Once the hypercalcemic crisis has resolved, or in patients with milder calcium elevations, longterm therapy can be initiated. Parathyroidectomy remains the definitive therapy for primary hyperparathyroidism. As described below, a Ca mimetic that stimulates the CaSR is a promising therapy for hyperparathyroidism. If the hypercalcemia results from malignancy, therapy ideally is directed at the underlying cancer. When this is not possible, intermittent dosing of parenteral bisphosphonates has been used to keep serum Ca within an acceptable range. 

In chronic renal failure treated by renal transplantation, hyperparathyroidism may persist, as discussed above. In most cases, the parathyroid glands involute to normal within 3 years (11,59,M,, 66). However, since severe or prolonged hypercalcemia impairs renal function and may cause permanent renal graft injury, subtotal parathyroidectomy must be considered for patients with persistent hypercalcemia or acute hypercalcemic crisis. 

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