Hyponatremia is a medical term which defines low blood or serum sodium level. Serum sodium level is considered low when it reaches below 135 mEq/liter. Hyponatremia is the most common electrolyte abnormality observed in cancer patients. According to a study from a comprehensive cancer center, 47% of cancer patients who are admitted to hospitals experience hyponatremia. Patients with hyponatremia may experience many morbidities including nausea, vomiting, headache, fatigue, falls, confusion and even seizures in severe cases. Studies also show that survival in cancer patients who have hyponatremia is poorer than cancer patients with normal serum sodium levels. Therefore, it is crucial that hyponatremia in cancer patients is treated by an expert in a timely fashion.
Hyponatremia is commonly seen in patients with lung, head and neck, gastrointestinal, breast, kidney cancers and lymphoma. Hyponatremia is caused by disequilibrium between body salt and water; either from loss of body salt or from relative or absolute excess of body water. In cancer patients hyponatremia can be due to cancer itself or due to chemotherapy. Several types of cancers cause excessive production of antidiuretic hormone (ADH) leading to a condition called SIADH (syndrome of inappropriate ADH release). The major role of ADH hormone is to retain water in the body, so when its production is increased, excessive water retention dilutes salt concentration resulting in hyponatremia. ADH hormone production can also be increased due to chemotherapy. Vincristine, Vinblastine, Ifosfamide, Cisplatin, Melphalan and Cyclophosphamide are among the chemotherapeutic agents known to cause SIADH and hyponatremia. Newer cancer treatments such as immunotherapy (Ipilimumab, Nivolumab, Pemrolizumab, etc.) can also lead to hyponatremia through disruption of other hormones such as ACTH and cortisol which also have roles in balancing blood sodium levels. Moreover, nausea and pain which are commonly seen in cancer patients can stimulate ADH hormone production and lead to hyponatremia.
Treatment of hyponatremia requires management by an expert as both hyponatremia itself and rapid correction of hyponatremia can yield to severe medical conditions. Nephrologists are the experts that treat electrolyte abnormalities including hyponatremia.
