Electrolytes

Original Editor - Lucinda hampton

Top Contributors - Lucinda hampton and Kim Jackson  

Introduction

An electrolyte: Any of various ions, such as sodium, potassium, or chloride, required by cells to regulate the electric charge and flow of water molecules across the cell membrane[1].
Membrane potential ions (id).jpg

Electrolytes are essential for basic life functioning, such as:

  • Maintaining electrical neutrality in cells
  • Generating and conducting action potentials in the nerves and muscles.
  • Essential for keeping your nervous system and muscles functioning.
  • Ensuring that your body’s internal environment is optimal by keeping you hydrated and helping regulate your internal pH.
  • Sodium, potassium, and chloride are the significant electrolytes along with magnesium, calcium, phosphate, and bicarbonates.

Electrolytes come from our food and fluids.

  • These electrolytes can have an imbalance, leading to either high or low levels. High or low levels of electrolytes disrupt normal bodily functions and can lead to even life-threatening complications.[2]
  • Most people meet their electrolyte needs through a balanced diet, though imbalance may occur if you’re dehydrated due to illness or excess heat.[3]

The term electrolyte means that this ion is electrically-charged and moves to either a negative (cathode) or positive (anode) electrode:

  • Cations are positively charged
  • Anions are negatively charged[3]

Function

Kidney nephron molar transport diagram.png

Electrolytes are important because they are what your cells (especially nerve, heart, muscle) use to maintain voltages across their cell membranes and to carry electrical impulses (nerve impulses, muscle contractions) across themselves and to other cells. Your kidneys work to keep the electrolyte concentrations in your blood constant despite changes in your body.

Eg. When you exercise heavily, you lose electrolytes in your sweat, particularly sodium and potassium. These electrolytes must be replaced to keep the electrolyte concentrations of your body fluids constant[3].

Complications

  • Both hyponatremia and hypernatremia, as well as hypomagnesemia, can lead to neurological consequences such as seizure disorders.
  • Hypokalemia and hyperkalemia, as well as hypocalcemia, are more responsible for arrhythmias.
  • Bicarbonate imbalance can lead to metabolic acidosis or alkalosis[2].

Indication for Analysis

Indications to order serum electrolyte panel are numerous. Some of which include:

  • As a part of routine blood investigations
  • For in-patients and ICU patients, the monitoring of serum electrolytes often occurs daily or more frequently as they can be affected by the medications, fluid therapy, diet changes, and illnesses.
  • Any illness that can cause electrolyte derangement eg.malnutrition, gastrointestinal disorders, cardiac disorders, kidney dysfunction, endocrine disorders, circulatory disorders, lung disorders, acid-base imbalance
  • Arrhythmias, cardiac arrest
  • Use of diuretics or any medications that can interfere with fluid and electrolyte homeostasis[2]

Electrolyte Imbalances

The most common electrolyte imbalances are in sodium and potassium. Electrolyte imbalances are referred to with the prefixes "hypo" (low) and "hyper" (high), combined with the scientific name of the electrolyte.

Sodium.jpg

Hyponatremia (low sodium)

  • The most common electrolyte imbalance, is a symptom of kidney disease.
  • Caused by eg. other disorders, some medications or when a person drinks too much water without consuming enough salt (especially during hot weather, when more sweating occurs).
  • The first symptoms are headache, fatigue, weakness and nausea.
  • More severe cases can result in confusion, seizure, coma and death.
  • Low sodium is treated by giving sodium and water intravenously.

Hypernatremia (high sodium)

  • Can be caused by excessive fluid loss, diabetes, diarrhea, excessive vomiting and some medications.
  • Thirst is typically the first symptom, and many of the other symptoms are the same as low sodium.
  • Older hospitalized patients are particularly susceptible to hypernatremia.
  • Treatment involves slowly replenishing water loss, usually over 48 hours, through drinking or intravenous administration.

Hypokalemia (low potassium)

  • Is most commonly caused by some diuretics (medicines that help rid the body of excess sodium and water).
  • Other causes include diarrhea, dietary deficiency and excessive sweating.
  • Symptoms include irregular heartbeat, muscle pain, general discomfort or irritability, weakness and paralysis.
  • Treatment can include potassium supplements, foods rich in potassium, or intravenous potassium and water.
  • People who experience hypokalemia because of a diuretic may be given another type of diuretic that doesn't have potassium loss as a side effect.

Hyperkalemia (high potassium)

  • Much more serious than hypokalemia.
  • Usually caused by kidney failure or medications that reduce the amount of potassium excreted by the kidneys.
  • High potassium can cause dangerous changes in the heart's function eg Heart Failure.
  • Other symptoms include tingling in the extremities, weakness and numbness.
  • Treatment includes drugs that cause the body to eliminate potassium. In the case of severe or worsening hyperkalemia, treatment must be started [4]immediately.

Main Electrolytes

Sodium (Na+)

  • An osmotically active anion, is one of the most important electrolytes in the extracellular fluid. It is responsible for maintaining the extracellular fluid volume, and also for regulation of the membrane potential of cells. Sodium is exchanged along with potassium across cell membranes as part of active transport.
  • Among the electrolyte disorders, hyponatremia is the most frequent.

Potassium (K+)

  • Mainly an intracellular ion. The sodium-potassium adenosine triphosphatase pump has the primary responsibility for regulating the homeostasis between sodium and potassium, which pumps out sodium in exchange for potassium, which moves into the cells.
  • Potassium disorders are related to cardiac arrhythmias.
Milk.jpg

Calcium (Ca2+)

  • Has a significant physiological role in the body.
  • Involved in skeletal mineralization, contraction of muscles, the transmission of nerve impulse, blood clotting, and secretion of hormones.
  • The diet is the predominant source of calcium. It is mostly present in the extracellular fluid.
  • See also Hypercalcemia

Bicarbonate (HCO3-)

  • The acid-base status of the blood drives bicarbonate levels.
  • The kidneys predominantly regulate bicarbonate concentration and are responsible for maintaining the acid-base balance.
  • Diarrhea usually results in loss of bicarbonate, thus causing an imbalance in acid-base regulation.

Magnesium (Mg2+)

  • Magnesium is an intracellular cation.
  • Magnesium is mainly involved in ATP metabolism, contraction and relaxation of muscles, proper neurological functioning, and neurotransmitter release.
  • When muscle contracts, calcium re-uptake by the calcium-activated ATPase of the sarcoplasmic reticulum is brought about by magnesium.
  • See also Hypomagnesemia

Chloride (Cl 1-)

  • An anion found predominantly in the extracellular fluid.
  • The kidneys predominantly regulate serum chloride levels.

Phosphorus (P)

  • An extracellular fluid cation.
  • Eighty-five percent of the total body phosphorus is in the bones and teeth in the form of hydroxyapatite; the soft tissues contain the remaining 15%.
  • Phosphate plays a crucial role in metabolic pathways.
  • It is a component of many metabolic intermediates and, most importantly of adenosine triphosphate(ATPs) and nucleotides[2].

References

  1. Wordnik Electrolyte Available from: https://www.wordnik.com/words/electrolyte (last accessed 16.11.2020)
  2. 2.0 2.1 2.2 2.3 Shrimanker I, Bhattarai S. Electrolytes. InStatPearls [Internet] 2020 Jan 20. StatPearls Publishing.Available from:https://www.ncbi.nlm.nih.gov/books/NBK541123/ (last accessed 14.11.2020)
  3. 3.0 3.1 3.2 Howstuffworks Electrolytes Available from:https://health.howstuffworks.com/wellness/diet-fitness/information/question565.htm (last accessed 14.11.2020)
  4. How stuff works Electrolytes 101 Available from:https://health.howstuffworks.com/wellness/diet-fitness/information/electrolyte.htm (last accessed 14.11.2020)