Side Effect: Low Blood Sodium (hyponatremia)

What is Low Blood Sodium (hyponatremia)?

Low blood sodium level, also known as hyponatremia, is a medical condition characterized by a lower than normal concentration of sodium (Na⁺) ions in the blood.

• The normal range for blood sodium levels is typically between 135 - 145 mEq/L.
• Low sodium (hyponatremia) is defined as a blood sodium level that is lower than 135 mEq/L.

What does Low Blood Sodium (hyponatremia) look like?

Hyponatremia can cause a wide range of symptoms, including nausea, vomiting, dizziness, weakness, muscle cramps, headache, confusion, seizures, and even coma. In severe cases, it can be life-threatening. Symptoms may depend upon how quickly the Na⁺ levels in the blood drop, and how low they get.

Who gets Low Blood Sodium (hyponatremia)?

There are several risk factors for hyponatremia in cancer patients. In many cases, several risk factors are present in patients who experience hyponatremia. Risk factors include:

• Syndrome of inappropriate antidiuretic hormone secretion (SIADH). A paraneoplastic syndrome that can often be seen in patients with lung cancer.
  • This can cause severe hyponatremia (very low sodium levels)
• Metastasis to the brain or adrenal glands
• Certain chemotherapy treatments
• Use of certain diuretics, opioid pain medications, antibiotics, non-steroidal anti-inflammatory drugs (NSAIDs), antipsychotics, antidepressants, and seizure medications
• Concomitant diseases such as heart failure, kidney failure, liver cirrhosis, increased thyroid or cortisol levels, and pneumonia
• Patients who receive maintenance IV fluid in the hospital may experience low sodium levels if they receive too much, or if the sodium in the fluid is not balanced with what their body needs.
  • 0.9% NaCl solution (also known as NS or “normal saline”), is often infused in the hospital to rehydrate patients when they are dehydrated.
  • Another common IV solution is known as D5NS, which is saline with 5% dextrose
    • If a solution containing less sodium, for example D5 ½ NS, is given in large amounts or for a long period of time, some patients may experience a lowering of sodium levels.

How to prevent Low Blood Sodium (hyponatremia)

The prevention of hyponatremia in cancer patients involves careful monitoring of fluid intake and output, IV fluid type, treating underlying medical conditions, and adjusting any possible contributing medications.

How to treat Low Blood Sodium (hyponatremia)

The treatment of hyponatremia in patients with cancer starts with addressing the underlying cause. Additional treatment approaches include fluid restriction, concentrated intravenous saline solutions, salt tablets taken by mouth, careful use of diuretics, or medications such as tolvaptan (Samsca®) and conivaptan (Vaprisol®).

If Na⁺ are very low, raising the sodium levels in the blood must be done slowly over time as rapid increases can cause seizures, or life-threatening neurological damage.