Electrolyte balance - Overview: Nursing

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ELECTROLYTE BALANCE - OVERVIEW

KEY POINTS
NOTES
DEFINITION
  • Charged molecules, or ions
  • Many essential functions
    • Transmission of nerve impulses
    • Facilitating muscle contraction
    • Maintaining fluid osmolality
  • Maintaining electrolyte homeostasis essential for normal body functioning

ELECTROLYTES AND THEIR FUNCTIONS
  • Electrolytes are charged particles in body fluids 
    • Cations are positive
    • Anions are negative 
  • Measured in urine blood and cerebrospinal fluid 
  • Usually expressed in mEq per liter of fluid (mEq/L)
  • Sodium Na+ 
    • Main cation in extracellular fluid 
    • Maintains osmolality blood volume and pressure 
    • Works with potassium for membrane potential 
    • Normal range is 135 - 145 mEq/L 
  • Potassium K+ 
    • Main cation in intracellular fluid 
    • Maintains intracellular osmolality 
    • Supports neuromuscular and cardiac function 
    • Normal range 3.5 - 5 mEq/L
  • Calcium Ca2+ 
    • Helps release neurotransmitters and hormones 
    • Influences nerve and muscle excitability 
    • Supports muscle contraction and blood clotting 
    • Maintains strong bones and teeth 
    • Normal range 8.5 - 10.5 mg/dL
  • Magnesium Mg2+ 
    • Supports cardiac and skeletal muscle function 
    • Acts at neuromuscular junction 
    • Cofactor in carbohydrate metabolism 
    • Helps maintain calcium levels 
    • Normal range 1.3 to 2.1 mEq/L
  • Phosphate PO43- 
    • Works with calcium to form bones and teeth 
    • Component of ATP for energy metabolism 
    • Part of DNA and RNA nucleotides 
    • Normal range 3 - 4.5 mg/dL

MAINTENANCE OF ELECTROLYTE BALANCE
  • Electrolytes move to maintain fluid and ion balance 
  • Movement occurs by diffusion or active transport 
  • Diffusion 
    • Passive movement with concentration gradient 
    • No energy required for movement 
    • Simple diffusion example oxygen leaves cell 
    • Facilitated diffusion uses channel proteins 
  • Active transport 
    • Uses ATP to move ions against gradient 
    • Movement is from low to high concentration 
      • Sodium potassium pump maintains balance 

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Content Reviewers

Lisa Miklush, PhD, RNC, CNS,Janine Eagon MS, APNP, CNS, RNC-OB

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.

Finally, phosphate, or PO43-, works with calcium to form bones and teeth. It is also an essential component of adenosine triphosphate, or ATP, which is the body’s main energy source for cellular metabolism; and nucleotides, which make up DNA and RNA. Phosphate’s normal range is between 3 and 4.5 mg/dL.

Sources

  1. "Fundamentals of nursing (11th ed.)" Elsevier (2023)
  2. "Fundamentals of nursing (10th ed.)" Elsevier (2021)
  3. "Fundamentals of nursing: Active learning for collaborative practice. (3rd ed.)" Elsevier (2022)
  4. "Fundamentals of nursing: Active learning for collaborative practice. (3rd ed.)" Elsevier (2022)