Tumor-Related Hyponatremia

Abstract

Hyponatremia is an important and common electrolyte disorder in tumor patients and one that has been reported in association with a number of different primary diagnoses. The correct diagnosis of the pathophysiological basis for each patient is important because it significantly alters the treatment approach. In this article, we review the epidemiology and presentation of patients with hyponatremia, the pathophysiologic groups for the disorder with respect to sodium and water balance and the diagnostic measures for determining the correct pathophysiologic groups. We then present the various treatment options based on the pathophysiologic groups including a mathematical approach to the use of hypertonic saline in management. In cancer patients, hyponatremia is a serious co-morbidity that requires particular attention as its treatment varies by pathophysiologic groups, and its consequences can have a deleterious effect on the patient's health.

Diagnosis and Management of Hyponatremia in Cancer Patients

“…SIADH has been reported in ϳ3% of patients with head and neck cancer (HNC) [34], most often in patients with lesions in the oral cavity and less frequently in those with lesions in the larynx, nasopharynx, hypopharynx, or other sites [35]. SIADH has also been identified in patients with a wide variety of other solid tumors and hematological malignancies, but at lower rates than those found with SCLC or HNC [2,10]. Besides cancer, SIADH may be caused by a variety of other conditions, including central nervous system (CNS) disorders (e.g., inflammatory or demyelinating diseases, subarachnoid hemorrhage, head trauma), pulmonary disorders (e.g., tuberculosis, pneumonia, acute respiratory failure, positive-pressure ventilation), HIV infection, and prolonged strenuous exercise [3,28].…”

“…Most cases reflect impaired water excretion, in which the capacity of the kidneys to eliminate water does not keep up with water intake, but in a minority of cases hyponatremia is driven by excessive water intake. Hyponatremia is often caused by SIADH in cancer patients [2,10]. In this setting, ectopic secretion of AVP (also known an antidiuretic hormone [ADH]) by tumor cells appears to be important in driving the hyponatremic state.…”

“…These salt wasting syndromes are often difficult to distinguish from SIADH because each is characterized by low plasma and sodium osmolality, high urine sodium concentration, and higher urine than plasma osmolality. However, the distinction is important because their management differs, and choosing the wrong management approach can lead to worsening of the hyponatremia, with potential adverse consequences [2].…”

“…Hyponatremia is an electrolyte abnormality commonly encountered in oncology practice and is usually defined by a serum sodium level Ͻ135 mEq/L [1,2]. Although many cases are asymptomatic, hyponatremia may cause neurological symptoms, particularly when serum sodium declines rapidly or by a substantial extent [3].…”

Symptomatic Hyponatremia as the Initial Presentation of Small Cell Lung Carcinoma: A Case Report of Delayed Diagnosis

“…3 SIADH is a diagnosis of exclusion caused by an increased amount of ADH or an increased renal sensitivity to the hormone. 8 The following criteria, known as the Bartter-Schwartz criteria, can be used to help differentiate SIADH from other causes of hyponatremia and includes: [4][5][6][7] • Euvolemia • Natriuresis (urine Na+ >20mEq/L)…”