[Treatment for the electrolytic disorders in cancer patients]

The most frequent electrolytic disorders associating with tumors are hypercalcemia and hyponatremia, which should often be dealt with on an emergency basis. Hypercalcemia is observed in around 10% of metastatic solid tumors including lung, breast, head and neck and renal cancers. In hematological malignancies, hypercalcemia is observed with a relatively high incidence in malignant lymphoma. Hypercalcemia is caused by bone metastasis or PTH-rP secreted from tumors. In other cases, it is induced by calcitriol produced from tumor. Hypercalcemia sometimes results in a fatal outcome, and should be carefully monitored. Hyponatremia presented as SIADH is sometimes caused by arginine vasopressin derived from tumors. In other cases, SIADH is induced with chemotherapeutic drugs such as cyclophosphamide and cisplatin. Neither hypercalcemia nor hyponatremia has any specific symptoms. Delayed treatment often results in severe condition, such as unconsciousness or even death. Therapy for hypercalcemia is started by infusion of normal saline, and a patient with severe hypercalcemia should be treated with bisphosphonates. Zoledronic acid is the best bisphosphonate among them at this present. Treatment of SIADH is started by water restriction. In an emergency, treatment with hypertonic saline(3-5%)should be considered together with loop diuretics. Demethyl chlorotetracycline is considerable in poor response cases, and mozavaptan hydrochloride is applicable in case of vasopressin-producing tumors. In any case, inappropriate rapid correction of hyponatremia could induce severe brain damage called CPM without careful management.