Electrolyte balance - Overview: Nursing

Electrolytes are charged molecules, or ions, that have many essential functions throughout the body, including transmission of nerve impulses, facilitating muscle contraction, and maintaining fluid osmolality. Because of their critical functions, maintaining electrolyte homeostasis is essential for normal functioning of the body.

Okay, let’s review the major electrolytes and their functions. They can be categorized as either cations, which are positively charged, like sodium; or anions, which are negatively charged, like phosphate. Electrolytes can be measured in the urine, cerebrospinal fluid, and blood, and they’re usually expressed as milliequivalents per liter of fluid, mEq/L.

So, first, there’s sodium, or Na+, which is the main cation in the extracellular fluid.  

It’s responsible for maintaining the extracellular fluid’s osmolality, or the concentration of the particles dissolved in the fluid, so it determines blood volume and blood pressure.  

Sodium also works closely with potassium, or K+, to maintain the cell’s resting membrane potential, which is the distribution of ions on either side of the cellular membrane. Sodium’s normal value is 135 to 145 mEq/L. Now, potassium is the main cation in the intracellular fluid, and it’s responsible for maintaining intracellular osmolality. Potassium is also essential for normal neuromuscular and cardiac function, and its normal range is between 3.5 and 5 mEq/L. 

Then there’s calcium, or Ca2+, which helps with releasing neurotransmitters from neurons, as well as releasing hormones from endocrine glands. It influences the excitability of nerve and muscle cells and is essential for muscle contraction. It’s also involved in blood clotting and maintaining strong bones and teeth. Calcium’s normal range is between 8.5 and 10.5 mg/dL.

Now, magnesium, or Mg2+, influences the function of both cardiac and skeletal muscles through its actions in the neuromuscular junction, which is where muscles and nerves meet. It also acts as a cofactor in lots of enzyme reactions during carbohydrate metabolism; and it helps maintain a normal calcium level. Magnesium normally ranges between 1.3 and 2.1 mEq\L.