Electrolytes are chemicals in the body that regulate important physiological functions. Examples of electrolytes are sodium, chloride, magnesium, potassium and calcium. Electrolyte imbalance causes a variety of symptoms that can be severe. Electrolyte imbalance is commonly caused by loss of body fluids through prolonged vomiting, diarrhea, sweating or high fever. The most serious forms of electrolyte imbalance in cancer patients include high blood calcium levels, called hypercalcemia, or a disorder called tumor lysis syndrome that results in electrolyte imbalance from the killing of cancer cells. Both of these can be life-threatening if not managed appropriately.
- What are electrolytes?
- What causes electrolyte imbalance?
- What are the symptoms of electrolyte imbalance?
- Which electrolyte disorders are most serious for cancer patients?
Electrolytes are chemicals in the body that regulate important physiological functions and include sodium, chloride, magnesium, potassium and calcium. When dissolved in water, electrolytes separate into positively and negatively charged ions. Nerve and muscle function are dependent upon the proper exchange of these ions in and out of the cells.
Electrolytes must exist in the body within a narrow concentration range in order to effectively serve a variety of critical functions (see table 1). The normal range is measured per liter of blood. Electrolyte imbalance refers to a value higher or lower than the normal range and can cause a variety of symptoms.
Table :1 Functions of electrolytes and their normal ranges
|Electrolyte||Functions in the body||Normal adult range*|
|Calcium||Necessary for muscle contraction, nerve function, blood clotting, cell division, healthy bones and teeth||4.5-5.5 mEq/L|
|Chloride||Maintains fluid balance in the body||97-107 mEq/L|
|Potassium||Regulates heart contraction, helps maintain fluid balance||3.5-5.3 mEq/L|
|Magnesium||Necessary for muscle contraction, nerve function, heart rhythm, bone strength, generating energy and building protein||1.5-2.5 mEq/L|
|Sodium||Maintains fluid balance and necessary for muscle contraction and nerve function||136-145 mEq/L|
*Values may vary from laboratory to laboratory.
Electrolyte imbalance is commonly caused by loss of body fluids through prolonged vomiting, diarrhea, sweating, or high fever. All of these may be side effects of chemotherapy treatment.
The kidneys play a critical role in regulating electrolytes. They control the levels of chloride in your blood and “flush out” potassium, magnesium and sodium. Therefore, a disturbance in blood levels of these electrolytes may be related to kidney function.
An electrolyte imbalance may lead to a number of symptoms that depend on which electrolyte is out of balance and whether the level is too high or too low. If you have altered potassium, magnesium, sodium or calcium levels, you may experience one or more of the following symptoms:
Hypercalcemia: A high level of calcium in the blood, called hypercalcemia, may become a medical emergency. This disorder is most commonly caused by cancer or parathyroid disease. Hypercalcemia resulting from cancer is particularly common in conjunction with breast cancer, lung cancer or multiple myeloma and often results from the destruction of bone due to bone metastases.
Signs and symptoms of hypercalcemia may include:
These many signs and symptoms are commonly attributed to either the cancer treatment or the cancer itself and may make it difficult for doctors to detect hypercalcemia when it first occurs. This disorder can be severe and difficult to manage. Severe hypercalcemia is a medical emergency requiring immediate treatment.
Tumor lysis syndrome: When cancer cells are killed by therapy, they may spill their inner (intracellular) contents, which accumulate in the body faster than can be eliminated. These excess intracellular contents cause the metabolic and electrolyte disturbances that result in tumor lysis syndrome (TLS). TLS can result in life-threatening complications if not managed appropriately. If TLS is untreated, its progression may cause acute kidney failure, cardiac arrhythmias, seizures, loss of muscle control or death.
Some patients with TLS may have initial symptoms including:
Other patients feel no symptoms of TLS in its early stages, but have abnormal laboratory results. Laboratory results indicative of TLS show high potassium, uric acid and phosphorous levels and low calcium levels in the blood.
Patients at a high risk of developing TLS typically have acute leukemia or lymphoma that is very responsive to chemotherapy. Patients with pre-existing kidney dysfunction are also at an increased risk of developing TLS. Patients who are considered to be at risk of developing TLS are typically treated with preventive measures prior to and during their treatment for cancer. Preventive measures typically include intravenous hydration, medications including allopurinol or Elitek® (rasburicase), and alkalinization of the urine with sodium bicarbonate.
Once TLS has actually developed, a patient is also treated for the specific medical abnormality that is present, which typically includes one of the following:
- High uric acid (hyperuricemia)
- High potassium (hyperkalemia)
- High phosphate (hyperphosphatemia)
- Low calcium (hypocalcemia)
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