Serum Electrolytes

By Tammy Hunter, DVM; Kristiina Ruotsalo, DVM, DVSc, Dip ACVP & Margo S. Tant BSc, DVM, DVSc

What are electrolytes?

Electrolytes are the salts and metallic components that are dissolved within the blood serum (serum is the liquid portion of blood).

The negatively charged electrolytes are balanced by the positively charged electrolytes.


What are the most commonly measured electrolytes?

The electrolytes of greatest clinical importance are sodium, potassium, chloride, bicarbonate, phosphorus, and calcium.


Why are electrolytes important?

Electrolytes are involved in most of the body's daily functions. For example, electrolytes are required for proper nerve conduction, for heart and skeletal muscle contraction, for maintenance of proper hydration status, and for maintenance of proper blood pH.


What samples are required for electrolyte determination?

A single blood sample is all that is required. This sample may be analyzed in the veterinary clinic or sent to a veterinary referral laboratory for electrolyte determination.

What do changes in electrolyte concentrations mean?

In most instances, changes in electrolyte concentrations do not indicate any one specific disease. Rather, changes in electrolyte concentrations occur as secondary changes caused by certain diseases or conditions. Serum calcium concentrations may become elevated from inflammation, cancer, or a condition called hyperparathyroidism. Diseased kidneys may be unable to eliminate excess phosphorus and potassium through the urine and result in an increase in one or both of these electrolytes. Diarrhea may cause an increased loss of sodium and bicarbonate from the gastrointestinal tract.

Occasionally the pattern of electrolyte change may point to a specific disease. As an example, an alteration in the ratio of sodium to potassium may suggest hypoadrenocorticism (Addison's disease) in dogs.


If electrolyte changes don't indicate what the disease process is, why bother measuring them?

Alterations in electrolyte concentrations may have significant consequences, because of their role in muscle contraction, nerve conduction, and water balance. Markedly elevated serum potassium concentrations can lead to cardiac arrhythmias (abnormal heartbeats). Excessive loss of sodium and chloride may result in dehydration and shock. A depleted phosphorus concentration in the diabetic patient may lead to red blood cell rupture and anemia.

"Alterations in electrolyte concentrations may have significant consequences, because of their role in muscle contraction, nerve conduction, and water balance."

It is important therefore to detect changes in electrolyte concentrations so that these alterations can be treated prior to the situation becoming severe or life threatening. Often these electrolyte changes must be attended to first, before the underlying disease condition is controlled or treated.

Related Articles