Cat & Dog - Serum Electrolytes

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

Why are electrolytes important?

They are involved in many of the body's important functions.  For example, electrolytes are required for the working of the nerves, muscles, and for maintenance of correct fluid balance in the body.

Will the sample have to be sent away?

This depends upon the particular tests required.  Today, many of the tests can be done at the practice.

What do these electrolyte measurements indicate?

Changes in electrolyte balance often occur with certain diseases or conditions.  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 noted in the blood tests.  Diarrhoea results in a loss of sodium and bicarbonate from the gastro-intestinal tract (gut).  This results in low values for these ions (electrolytes) in the blood tests.  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 (Addison's disease) in dogs.

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

Due to their role in the efficient functioning of the body, particularly with respect to 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.