Electrolytes

Electrolytes are chemicals that dissolve in water and dissociate into their positive and negative ions (an element that carries an electrical charge).

Most electrolytes are inorganic salts, acids, and bases found in all body fluids. Organic compounds are usually non-electrolytes, meaning that they do not ionize in a solution.

Positive ions are called cations (sodium Na+, potassium K+, calcium Ca+2, magnesium Mg+2 , iron Fe+2 , and hydrogen H+ ). In intracellular fluid, the most abundant cation is potassium. In both tissue fluid and plasma, the most abundant cation is sodium.

Negative ions are called anions (chloride Cl¬, bicarbonate HCO₃-, sulfate SO₄-2, phosphate HPO₄-2, and protein anions). In intracellular fluid, the most abundant anion is HPO₄-2, along with protein anions. In both tissue fluid and plasma, the most abundant anion is chloride. Protein anions form a significant part of plasma, but not of tissue fluid.

Electrolytes help regulate the osmosis of water between water compartments. Some are involved in acid-base regulations. They can also be part of the structural components of tissues or enzymes.

Major electrolytes and their functions

Sodium (Na+) creates most of the osmotic pressure of extracellular fluid (ECF), and is the most abundant cation in ECF. It is essential for electrical activity of neurons and muscle cells. The primary mechanism regulating sodium concentration is aldosterone, which stimulates the distal tubule of the nephron unit to reabsorb sodium. Imbalances cause hypo- or hypernaturemia.
- Hyponaturemia is a consequence of excessive sweating, diarrhea, or vomiting causing dizziness, confusion, weakness, low BP, and shock.
- Hypernaturemia is a consequence of excessive water loss or sodium ingestion, causing a loss of ICF characterized by extreme thirst and agitation.
Potassium (K+) creates most of the osmotic pressure in intracellular fluid (ICF), and is the most abundant cation in ICF. It is essential for electrical activity of neurons and muscle cells. The primary substance regulating potassium concentration is aldosterone, which stimulates the distal tubule of the nephron unit to excrete potassium. Imbalances cause hypo- or hyperkalemia.
- Hypokalemia is a consequence of vomiting, diarrhea, or kidney disease causing fatigue, confusion, and possible cardiac failure.
- Hyperkalemia is a consequence of Addison's disease causing weakness, abnormal sensations, and cardiac arrhythmias with possible arrest.
Calcium (Ca+2) - 98% of the body’s calcium is found in bones and teeth. It maintains normal excitability of neurons and muscle cells and is essential for blood clotting. The primary regulator of plasma levels of calcium stems from the parathyroid hormone. Imbalances cause hypo- or hypercalcemia.
- Hypocalcemia is a consequence of hypoparathyroidism or decreased calcium intake, which results in muscle spasms leading to tetany.
- Hypercalcemia is a consequence of hyperparathyroidism resulting in muscle weakness, bone fragility, and possible kidney stones.
Magnesium (Mg+2) – 50% of the body’s magnesium is found in bone. It is the most abundant cation in ICF and essential for ATP production as well as activity of neurons and muscle cells, especially the heart.
Chloride (Cl¬) is the most abundant anion in ECF. It diffuses easily into and out of cells. It helps regulate osmotic pressure. Chloride is a part of HCl (hydrochloric acid) in gastric juices and tends passively to follow sodium.
Bicarbonate (HCO₃-) is an important anion of the bicarbonate buffer system. It is the form used to transport carbon dioxide in the blood. Excretion is controlled by the kidneys and can be reabsorbed, if the need arises.
Phosphate (HPO₄-2) – 85% of the body’s phosphate is found in bones and teeth. It is primarily an ICF anion. Phosphate is part of DNA, RNA, ATP, and phopholipids, as well as the phosphate buffer system.
Sulfate (SO₄-2) is part of some amino acids and proteins.

pH Changes: (change; cause; compensation)

Acidosis:
- Metabolic – kidney disease, ketosis, diarrhea, vomiting – increased respirations to exhale carbon dioxide
- Respiratory – decreased rate of efficiency, emphysema, asthma, pneumonia, paralysis of respiratory muscles – kidneys excrete hydrogen ions and reabsorb sodium ions and bicarbonate ions
Alkalosis:
- Metabolic – over-ingestion of bicarbonate medications, gastric suctioning – decreased respirations to retain carbon dioxide
- Respiratory – increased rate of respiration (hyperventilation), anxiety, high altitude – kidneys retain hydrogen ions and excrete sodium ions and bicarbonate ions

This page was updated in November 2005.