[Palliative therapy in cancer. 4. Palliation of the symptoms from a malignant tumor. (2)]

Patients suffering from malignant disease will probably develop some metabolic abnormality of electrolytes. Hypernatremia is defined as an elevation of serum natrium over 150 mEq/l and caused by decrease of water intake, low level of ADH secretion and impaired response of kidney to ADH. Hyponatremia below 135 mEq/l of serum natrium is caused by SI-DAH, sick cell syndrome and increased loss of natrium from the kidney. On the other hand, hyperkalemia is defined as an elevation of serum kalium over 5.0 mEq/l and caused by acute tumor cell lysis syndrome, adrenal and renal insufficiency. Hypokalemia is caused by kalium loss from kidney and hypersecretion of mineral corticoid. Hypercalcemia is found in the high frequency among patients with malignant disease. Hypercalcemia is defined as an elevation of serum calcium over 11.0 mg/dl, although the most important aspect is the level of ionized calcium. The excess calcium causes defective urinary concentration with polydipsia, nausea and vomiting leading to volume depletion. At serum calcium levels about 13.8 mg/dl, there may be rapid deterioration or renal function, dehydration, coma and cardiac arrhythmias. Hypercalcemia is rarely the first manifestation of cancer. There are three principle pathogenic causes of malignant hypercalcemia, 1) hypercalcemia is a feature of several hematological cancers, including Burkitt's lymphoma, T cell leukemia, but most commonly with myeloma. The hypercalcemia in these myeloma patients is due to the secretion of an osteoclast activator, a lymphokine by the myeloma cells. 2) all patients with bony metastases have biochemical evidence of increased bone resorption. However, not all patients with bony metastases develop hypercalcemia. Probably the hypercalcemia is due partially to increased renal tubular reabsorption of calcium, mediated by a humoral factor, with activity similar to that of parathormone. 3) hypercalcemia in the patients without bony metastases is due to increased bone resorption caused by the ectopic secretion by the tumor. Mildly symptomatic patients will benefit from modest salt loading. They are dehydrated and replacement of the extracellular fluid is the first line of treatment. This may require 4-10 l normal saline/24 h. In addition, frusemide will increase calcium excretion. Calcitonin may be given subcutaneously or intravenously to refuse the mobilisation of calcium from bone. Glucocorticoids are unhelpful, but will prolong the effect of calcitonin. A diphosphonate is also useful.