Updated August 4, 2016
Electrolytes are found in various fluid containers such as sports drinks, car batteries and humans. These charged particles are atoms that have lost or gained an electron and are called ions. Recall that atoms in their neutral state have a core of positively charged protons that hold an equal number of negatively charged electrons in orbit.
If an atom loses electrons, it gets a positive charge as it has more positively charged protons in the core than negatively charged electrons in orbit, thus becoming a cation.
If the atom gains electrons, it gets a negative charge because it has more negatively charged electrons in orbit than positively charged protons in the core, thus becoming an anion.
For example, common salt dissolved in water splits into sodium and chloride ions. At separation, the sodium atom donates an electron to the chloride atom, forming positively charged sodium (Na+) cations and negatively charged chloride (Cl-) anions surrounded by water molecules.
If the water evaporates, the salt crystals will reform as the oppositely charged Na+ and Cl- ions get closer to each other and hook up to reform sodium-chloride (salt) crystals.
Human ions and function
We have common salt circulating in our body as Na+ and Cl- ions along with potassium (K+) bicarbonate (hydrogen-carbon-oxygen, or HCO3- ) and calcium (Ca++), which provide essential life functions.
Potassium and sodium are largely responsible for the cell membrane electrical charge (membrane potential) that conducts nerve signals to and from the brain and generates the brain’s electrical activity for interpretation of those signals producing recognition and reaction.
This electrical activity is why the green grass our eyes scan is the green grass our brain pictures for us, why the touch and temperature signal from a too-warm stove results in the muscle contraction required to move our hand away from harm and why our heart maintains a regular rhythm and effectively functions without conscious effort. These are just a few of the body functions accomplished with this electrical potential.
In addition to helping with the cell membrane charge, sodium is a key component for maintaining proper water balance in the body. You might have heard the “water follows sodium” rule referring to the renal regulation of body water by reabsorbing or excreting sodium during the formation of urine.
Hydrogen ions (H+) basically define an acid, and yes, water, or H2O, is mildly acidic. A base is the chemical opposite of an acid and can combine with the hydrogen ions to produce a neutral state. Bicarbonate is a base and, along with other acid neutralizers, maintains the body’s acid-base balance, or pH, within a very narrow range of normal.
Acids are formed during normal body functions, but excess acids need to be controlled, kind of like the devices on your car engine that help decrease emissions that over-pollute the air. The bicarbonate ion combines with acids to form carbon dioxide that is expelled by the lungs so we can maintain a normal pH. Although the kidneys will excrete some acid, more importantly they recover bicarbonate ions so we can recycle a steady supply to maintain proper acid-base balance.
Chloride ions are the major anion, or negative ion, in the body. Chloride helps regulate the body’s water balance along with sodium. You know that’s true any time you sweat and get that salty taste if a drop hits your lips. And those who drink urine (research it) will tell you it is a salty drink, again due to the sodium and chloride that go out with the water. The chloride ion also provides the stomach acid for digestion by combining with a positive hydrogen ion to form hydrochloric acid (H+ + Cl- = HCl).
Therapeutic uses
The same ions that circulate in our body become therapies for a variety of medical conditions. Normal saline (0.9 percent NaCl) is the fluid of choice for initial attack on hypotensive patients. Potassium chloride (KCL) is added to IV fluid to replace potassium in a patient with hypokalemia, sometimes called hypopotassemia. Sodium bicarbonate (NaHCO3) is given intravenously or added to IV fluid for treatment of severe acidosis or for hyperkalemia. Calcium chloride (CaCl2) may be used for treatment of hypocalcemia, hyperkalemia and hypermagnesemia.
Laboratory values
Electrolytes can be measured in the blood and are included in grouped tests like the basic metabolic panel, renal panel and comprehensive metabolic panel. Each laboratory has a normal range for their specific tests, but they will be close to the values noted below.
The levels are reported as milliequivalents, millimoles or milligrams depending on the lab. The important component is the numbers. Of course we like to see the numbers in the normal range, but a basic understanding of the problems that can occur when the results are out of bounds is obviously important.
Sodium
Na: 136-145millimoles/liter
Inadequate sodium intake or excessive loss through dehydration, sweating or urination may cause a low sodium level, or hyponatremia. In severe cases, this can result in life-threatening cerebral edema from inadequate circulating sodium to keep excess fluid out of the cells (recall that water follows sodium). Another cause for low sodium is the dilution of the sodium concentration from excessive body fluid.
Hypernatremia, or elevated plasma sodium levels, may occur when the body loses more water than sodium as with prolonged dehydration, excessive vomiting and some forms of diarrhea. Excessively high blood glucose levels induce large water losses via the kidneys and may result in elevated sodium levels. Less common is diabetes insipidus, a disorder of body water regulation resulting in life-threatening renal water loss.
Chloride
Cl: 98-107 millimoles/liter
Since chloride is so closely tied to sodium, many of the disorders that cause hyper- or hyponatremia cause the same increase or decrease in the level of chloride. Additionally, certain renal problems result in abnormal chloride levels.
Potassium
K: 3.5-5.1 millimoles/liter
Notice how the amount of potassium in our blood is much lower compared to the amount of circulating sodium. The reverse is true inside the cell, where most of our potassium is stored along with much less intracellular sodium. Again, it is the interaction with these two ions inside and outside of the cell membrane that produces the cell membrane potential.
Too much potassium in circulation alters the fine balance of the cell membrane charge, with the most serious effects on the heart rhythm, ranging from asymptomatic peaked T-waves to life-ending ventricular fibrillation. Hyperkalemia can develop from the ingestion of too much potassium, too little excretion through the kidneys or a combination of both. Renal disease patients and those on dialysis are at high risk for hyperkalemia.
One cause for abnormal potassium levels is not from a disease process but from errors in obtaining and/or handling the blood sample. The red blood cells rupture (hemolysis) and release their intracellular potassium in the blood draw tube or while the blood is being handled in the lab, causing a false elevation in the result.
Hypokalemia may come from over-excretion of potassium in the urine through diseased kidneys or with certain medications such as diuretics. Potassium loss may also come from the gastrointestinal tract (vomiting/diarrhea). Muscle weakness is a common complaint with significant hypokalemia, which may progress to paralysis or respiratory arrest.
Carbon dioxide (bicarb)
CO2(HCO3): 21-32 millimoles/liter
When you see CO2 on a metabolic or renal panel, think “bicarb” level in the venous blood, not the carbon dioxide gas or CO2 result you get from a blood gas machine. A low bicarbonate level tells us the body is using extra bicarbonate ions to neutralize an abnormal amount of body acid; thus we are acidotic. When the bicarb level is too high, we are alkalotic, the result of too much body bicarbonate. This condition occurs if excessive bicarbonate is ingested or infused or when an abnormally low internal acid level exists.
Abnormal acid loss may occur from increased renal acid excretion or with the loss of gastric acid from prolonged vomiting. This leaves more bicarbonate in the body than acid and produces alkalosis.
Calcium
Ca: 8.5-10.5 milligrams/deciliter (100ml)
Calcium is essential for muscle contraction and bone strength. Mild hypocalcemia is common and asymptomatic early on. Vitamin D deficiency and/or inadequate calcium intake is a common cause.
Severe hypocalcemia may cause irritable nerves and muscles that lead to muscle cramps, seizures and repeated muscle contractions called tetany. The most frequent cause of symptomatic low blood calcium is a malfunction of the calcium-regulating parathyroid glands.
Hypercalcemia, or too much calcium in circulation, may cause muscle weakness, altered mental status and kidney damage. The source for hypercalcemia is our own bones due to the effects of certain cancers, severe kidney disease or overactive parathyroid glands.
Summary
How something so small drives something as complex as life is hard to comprehend. Tiny electrically charged particles are ultimately responsible for our basic life functions, emotions, complex thought, physical movement and sensations of sight, smell, taste, touch and hearing.
But yet here we are, and to maintain how we are, for those who provide care wherever we are, it is important for us to understand the basics of how electrolytes light up our life.
Shocking, isn’t it?
