Serum Electrolytes

Electrolytes occur in the blood and are frequently measured during serum biochemistry. The most common electrolytes are sodium, potassium, magnesium, calcium, chloride, bicarbonate and phosphate.

Why are electrolytes important?

They are involved in most of the body's important functions. For example, electrolytes are required for proper nerve production and skeletal muscle contraction and for maintenance of correct water balance in the body.

Will the sample have to be sent away?

This depends upon the particular electrolytes. Today, most of the tests can often be done at the practice.

Why are these electrolyte concentration levels important?

Changes often occur secondarily to certain diseases or conditions. For example, increased serum calcium concentrations are often seen in cases of inflammation, cancer or a glandular (endocrine) condition known as hyperparathyroidism. If the patient has kidney problems excess phosphorus and potassium may not be eliminated in the urine. The increased levels will then be reflected in the blood tests. As a result of diarrhoea there is a loss of sodium and bicarbonate from the gastro- intestinal tract. This in turn will be reflected with low results for these electrolytes in the blood test. Sometimes the electrolyte change may be sufficiently specific to point to a particular disease. An example of this is the alteration in ratio of sodium to potassium which occurs with a condition known as hypoadrenocorticism (Addisons disease) in dogs.

If the electrolyte changes are unlikely to indicate the reason of my pet's condition, is it worth measuring them?

Due to their role in efficient functioning of the body, particularly in respect of muscle contraction, nerve conduction and water balance, electrolyte imbalance can have very profound effects. For example increased serum potassium can lead to serious heart abnormalities. Loss of sodium and chloride can quickly lead to dehydration and shock. In the diabetic animal, a serious fall in phosphorus concentration may lead to blood cell rupture (haemolysis) and profound anaemia. Therefore it is important that we are aware of any changes in electrolyte balance as soon as possible in order that the situation can be rectified before it becomes severe or life threatening. Once under control we can then investigate the underlying disease more fully.