electrolyte

1. A chemical compound that ionizes when dissolved or molten to produce an electrically conductive medium.
2. Physiology. 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.

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A material that conducts an electric current when it is fused or dissolved in a solvent, usually water. Electrolytes are composed of positively charged species, called cations, and negatively charged species, called anions. For example, sodium chloride (NaCl) is an electrolyte composed of sodium cations (Na⁺) and chlorine anions (Cl⁻). The ratio of cations to anions is always such that the substance is electrically neutral. If two wires connected to a light bulb and to a power source are placed in a beaker of water, the light bulb will not glow. If an electrolyte, such as sodium chloride, is dissolved in the water, the light bulb will glow because the solution can now conduct electricity. The amount of electric current that can be carried by an electrolyte solution is proportional to the number of ions dissolved. Thus, the bulb will glow more brightly if the amount of sodium chloride in the solution is increased. See also Ion.

Any substance that produces ions when dissolved is an electrolyte. These substances include ionic materials composed of simple monatomic ions, such as sodium chloride, or substances composed of polyatomic ions, such as ammonium nitrate (NH₄NO₃). When these substances are dissolved, hydrated ions are generated, as in reactions (1) and (2).
1

2

A special type of electrolyte is an acid, in which the cation is H⁺. When acids are dissolved in water, H⁺ ions are produced along with an anion, which can be either a monatomic ion, as in hydrochloric acid (HCl), or a polyatomic ion, as in nitric acid (HNO₃) or acetic acid (HC₂H₃O₂), as in reactions (3)–(5).
3

4

5

Electrolytes such as sodium hydroxide (NaOH) that yield the hydroxyl (OH⁻) anion when dissolved in water are called bases [reaction (6)]. Some molecules that do not contain ions, such as
6
ammonia (NH₃), generate OH⁻ ions when dissolved in water as in reaction (7); these bases are also electrolytes. Polar covalent
7
molecules, such as ethanol, dissolve in water but do not generate any ions and are called nonelectrolytes.

Many electrolytic substances completely dissociate into ions when they are dissolved in water. In these cases, the reactions shown above would proceed completely to the right, leaving only dissolved ions and no associated, electrically neutral molecules. For example, when sodium chloride is dissolved in water, all of the dissolved material is present as Na⁺ and Cl⁻ ions, with no dissolved NaCl molecules. Substances that completely dissociate are called strong electrolytes, because every molecule dissolved generates ions that contribute to the electrical conductivity. Ionic substances, such as NaCl and NH₄NO₃, are strong electrolytes. Acids and bases that completely dissociate are called strong acids and strong bases, and these substances are also strong electrolytes. Hydrochloric acid (HCl) and HNO₃ are strong acids, so every molecule of HCl or HNO₃ that dissolves generates a H⁺ cation and a Cl⁻ or NO₃⁻ anion, respectively.

Some substances dissolve in water but do not dissociate completely. For example, when acetic acid is dissolved in water, some molecules dissociate to form H⁺ and C₂H₃O₂⁻ ions, while others remain associated as C₂H₃O₂H units, which contain polar O-H bonds and are therefore readily soluble in water. Acids such as acetic acid that do not dissociate completely are called weak acids. Similarly, the reaction of ammonia with water in reaction (7) proceeds to only a small extent. Thus, some molecules of ammonia react with water to generate OH⁻ and NH₄⁺ ions, but many simply remain as NH₃. Since each dissolved molecule of ammonia does not generate an OH⁻ anion, ammonia is said to be a weak base. See also Ionic equilibrium.

In biological systems, electrolytes play important roles in regulating kidney function and the retention of water. Electrolytes are also vital for providing the electric current needed for nerve impulses in neurons.

A liquid, gelatinous or solid material that contains ions. In a battery, the electrolyte is the material that allows electricity to flow from one plate to another (between positive and negative electrodes). See lithium polymer and batteries.

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Chemically salts that dissociate in solution and will carry an electric current; clinically used to mean the mineral salts of blood plasma and other body fluids, especially sodium and potassium.

A solution that conducts electricity by means of its ions.

Brand names: Colyte®, GoLYTELY®, MoviPrep®, NuLYTELY®, OCL® Solution, PEG 3350 and Electrolytes™, TriLyte™

Español:
• Solución oral de polietilenglicol; electrólitos

Polyethylene Glycol; Electrolytes oral solution

What is polyethylene glycol; electrolytes oral solution?

POLYETHYLENE GLYCOL; ELECTROLYTES solutions (CoLyte®, GoLytely®, NuLytely®, Moviprep®, or TriLyte™) are laxative solutions that are used to cleanse the bowel before colonoscopy, surgery or other procedures. The solution may also be used to treat other intestinal problems as determined by your health care professional. This laxative helps increase the water content of the stool and bowel movements become easier and more frequent. The electrolytes in the solution (like potassium) help prevent important mineral losses from the body. Generic solutions are available.

What should I tell my health care provider before I take this medicine?

They need to know if you have any of these conditions:
• a history of blockage of the stomach or intestine
• a history of seizure
• current abdomen distension or pain
• difficulty swallowing
• diverticulitis, ulcerative colitis, or other chronic bowel disease
• glucose-6-phosphate dehydrogenase (G6PD) deficiency
• phenylketonuria
• an unusual or allergic reaction to polyethylene glycol, other medicines, dyes, or preservatives
• pregnant or trying to get pregnant
• breast-feeding

How should I take this medicine?

Follow the directions for using this medicine provided by your doctor.

Before using this medicine you or your pharmacist need to fill the container with the amount of water indicated on the package label. Shake well before use and before each dose. Take this laxative solution by mouth. Take exactly as directed. Your health care professional will tell you when to start drinking this solution prior to your procedure. You will usually need to drink a certain amount of the solution every 10 minutes until the stool is all watery and clear, or alternatively, until the solution is gone. It is best to drink each portion quickly rather than sipping it. Do not take your medicine less often or more often than directed. You will usually have the first bowel movement about 1 hour after you begin drinking the solution. After that, you will have frequent bowel movements as your bowel is cleans out.

Follow your prescribers instructions for what is allowable in the diet. Do not eat any solid food for at least 2 hours, and preferably 3—4 hours, before you begin drinking this medicine. You usually must drink only clear, non-red colored liquids from the time you start this solution until the time your procedure is complete. Also, do not eat until after your surgery or procedure is complete.

Contact your pediatrician or health care professional regarding the use of this medicine in children. Special care may be needed.

What if I miss a dose?

What drug(s) may interact with polyethylene glycol; electrolytes solution?

No specific drug interactions have been reported. However, if you regularly take other medications, check with your prescriber before taking this solution. Usually, only certain medications should be taken prior to the procedure; follow your health care providers instructions.

Tell your prescriber or health care professional about all other medicines you are taking, including non-prescription medicines, nutritional supplements, or herbal products. Also tell your prescriber or health care professional if you are a frequent user of drinks with caffeine or alcohol, if you smoke, or if you use illegal drugs. These may affect the way your medicine works. Tell your prescriber or health care professional before stopping or starting any of your medicines.

What should I watch for while taking polyethylene glycol; electrolytes solution?

Do not use this solution for longer than prescribed without advice from your prescriber or health care professional. See your healthcare professional for any changes in bowel habits, including constipation, that are severe or last longer than three weeks.

Do not inhale dust from the solution powder. This can make breathing difficult or may cause sneezing or an allergic-type reaction.

Drink plenty of clear liquids before, during, and after using this preparation. Otherwise, you can become dehydrated.

What side effects may I notice from taking polyethylene glycol; electrolytes solution?

Side effects that you should report to your prescriber or health care professional as soon as possible:
• difficulty breathing (rare)
• itching of the skin, hives, or skin rash (rare)
• seizure
• severe bloating, pain, or distension of the stomach
• vomiting

Side effects that usually do not require medical attention (report to your prescriber or health care professional if they continue or are bothersome):
• diarrhea or a frequent need to move the bowels are expected effects of this medication
• lower abdominal discomfort or cramps
• minor bloating
• nausea
• passing gas

Where can I keep my medicine?

Keep out of the reach of children in a container that small children cannot open.

While you are taking this medicine, store the solution in the refrigerator to improve the taste, do not freeze. Throw away any unused liquid medicine after 48 hours.

Last updated: 7/1/2002

Important Disclaimer: The drug information provided here is for educational purposes only. It is intended to supplement, not substitute for, the diagnosis, treatment and advice of a medical professional. This drug information does not cover all possible uses, precautions, side effects and interactions. It should not be construed to indicate that this or any drug is safe for you. Consult your medical professional for guidance before using any prescription or over the counter drugs.

A substance (acid, base, or salt) that can be dissolved in water and conducts an electric current. See also electrolyte drink.

Electrolytes are molecules that, in solution, dissociate into positively charged ions (cations) and negatively charged ions (anions). Principal ions in body fluids are sodium, potassium, and chloride. A 70 kg adult has a body content of approximately 100 g sodium, 140 g potassium, and 95 g chloride. To maintain a stable body content, the amount of principal ions lost must equal the amount consumed. During growth and during pregnancy, the amount accreted for tissue formation also must be considered.

Physiological Functions

Sodium is the predominant cation in fluids outside the cells (extracellular fluid), whereas potassium is the predominant cation in the intracellular fluid. Chloride is the major anion of the extracellular fluid. Sodium plays a central role in regulating body fluid balance and distribution of fluid between the extracellular and intracellular compartments. As sodium is the major osmotically active particle in the extracellular fluid, sodium and its accompanying anion determines the osmolar concentration, or osmolarity, of this compartment. An increase in sodium concentration will increase the osmolarity of the extracellular fluid, thus causing water to move out of the cells into the extracellular compartment. It will also cause water retention by stimulating the thirst mechanism and by decreasing urine flow. The opposite occurs when sodium concentration is decreased. Thus, sodium plays a central role in regulating body fluid balance and the distribution of fluid between the extracellular and intracellular compartments.

Potassium is necessary for normal growth and plays an important function in cell metabolism, enzyme reactions, and synthesis of muscle protein. Both sodium and potassium are involved in maintaining proper acidity (pH) of the blood and in maintaining nerve and muscle functions. Normal resting membrane potentials of nerve and muscle cells range between –50 and 100 mV, with the inside of the cells negative with respect to the outside. These resting membrane potentials are maintained by the chemical gradient of potassium across cell membranes. Activation of excitable cells alters their membrane permeabilities to sodium and potassium, leading to changes in their membrane potentials. A weak stimulus causes a small depolarization (the inside of the cell is made less negative) as a result of sodium influx along its electrochemical gradient via the voltage-gated sodium channels in cell membranes. This is followed by repolarization, which is a manifestation of potassium efflux. If the stimulus is sufficiently strong, large changes in the membrane potential occur, during which the membrane potential may change from –70 mV to +30 mV, and then repolarize back to its resting membrane potential. This action potential, cause by alternation of potassium steady-state potentials with pulsed sodium potentials, gives rise to a traveling wave of depolarization that is conducted along the nerve fiber to exert an effect on the effector cells it innervates (supplies with nerves). In muscles, action potential leads to muscle contraction.

Dietary sodium chloride in foods and beverages is absorbed mostly in the small intestine. Active transport of sodium out of the small intestinal epithelial cells across their basolateral membrane provides an electrochemical gradient for the absorption of sodium across the luminal membrane. Entry of sodium through carrier proteins can either transport other solutes against their concentration gradient in the same direction (co-transport) or in an opposite direction (counter-transport). A number of transporters have receptor sites for binding sodium and glucose, galactose, or amino acids. Therefore, entry of sodium across the luminal membrane also brings in a solute. Counter-transport mechanisms operating in the kidneys allow excess hydrogen and potassium to be excreted in the urine.

Consumption of Sodium, Chloride, and Potassium

Consumption usually exceeds the needs of an individual, although the amount consumed varies widely with dietary habits. Most natural foods contain high potassium content but are lower in sodium content (Table 1). American adults consume an average of 2.5 to 3.5 g of potassium daily. Individuals consuming large amounts of fruits and vegetables may have a daily intake of as high as 11 g. Sodium is consumed mainly as sodium chloride (table salt). A small amount is consumed as sodium carbonate, sodium citrate, and sodium glutamate. Intakes of sodium vary, averaging 2 to 5 g/day of sodium or 5 to 13 g/day of sodium chloride. Only about 10 percent of sodium intake is from natural foods, the rest from sodium salts added during cooking and at the table, and from salts added during processing of foods. In regions where consumption of salt-preserved foods is customary, intake of sodium can be as high as 14 to 20 g/day.

Under normal circumstances, about 99 percent of dietary sodium, chloride, and potassium is absorbed. Absorption occurs along the entire length of the intestine, the largest fraction being absorbed in the small intestine and the remaining 5 to 10 percent in the colon. Potassium is also secreted in the colon. Various homeostatic regulatory mechanisms, the most important of which is aldosterone, modulate the absorption of sodium and secretion of potassium.

Loss of Sodium, Chloride, and Potassium

Obligatory loss of fluids through skin, urine, and feces invariably causes loss of these ions. Minimal obligatory loss for an adult consuming average intakes has been estimated to be 115 mg/day for sodium and 800 mg/day for potassium. Over 95 percent of loss is in the urine. Under most circumstances, loss of chloride parallels that of sodium. Loss of these ions can increase greatly in diuresis, vomiting, and diarrhea. Loss of sodium chloride can also increase greatly from profuse sweating.

Recommended Intake. Daily minimum needs can be estimated from the amount required to replace obligatory (Table 2). The need is increased in infants and children, and during pregnancy and lactation. Estimated safe minimum intake levels are higher than the minimum requirements to account for the various degrees of physical activity of individuals and environmental conditions. Average intakes in the United States are higher than the estimated safe minimum levels of sodium chloride (1.3 g/day) and potassium (2 g/day).

Table 1

Table 2

The association of high salt intake with hypertension and the beneficial effects of potassium in hypertension has led to recommendations that daily intake of salt should not exceed 6 g and that of potassium should be increased to 3.5 g. This can be achieved by increasing intake of dietary fruits and vegetables.

Regulation of Sodium, Chloride, and Potassium Balance

Various mechanisms regulate excretion of these ions by the kidneys to maintain homeostatic equilibrium of body fluids. Urinary sodium excretion is controlled by varying the rate of sodium reabsorption from the glomerular filtrate by tubular cells, whereas potassium excretion is controlled by varying the rate of tubular secretion of potassium.

Abnormally low blood volume (hypovolemia) in sodium deficit increases renal sodium chloride reabsorption by increasing sympathetic discharge to the kidneys, and by stimulation of two hormonal systems, the renin-angiotensin-aldosterone and the antidiuretic systems. This results in the production of low urine volume with low sodium and chloride contents. Hypovolemia also initiates the thirst mechanism and increases an appetite for salt (or salt cravings).The presence of salt appetite in animals is to ensure an adequate intake of salt to protect the extracellular fluid volume from excessive loss of sodium due to sweating, diarrhea, pregnancy, or lactation. The development of salt appetite is of significance in the successful adaptation to a terrestrial life, especially in herbivorous animals. The need for salt can be satisfied by providing cattle and sheep with salt licks. Humans and other carnivores are less dependent on separate supplies of salt because dietary salt can be obtained from meat. However, they may develop a craving for salt when they are sodium deficient. This deficit-induced salt craving may be mediated by hormones acting on the brain and by changes in gustatory response. Abnormally high blood volume (hypervolemia) in sodium excess increases renal excretion of sodium chloride by suppression of sympathetic discharge to the kidneys, suppression of the renin-angiotensin-aldosterone and antidiuretic systems, and stimulation of the secretion of atrial natriuretic peptides.

Aldosterone is the most important hormone regulating secretion of potassium. Aldosterone secretion is triggered by angiotensin II, by high plasma potassium concentration, or by low plasma sodium concentration. Plasma concentrations of potassium and hydrogen also affect directly the secretion of potassium by the distal nephrons. The rate of potassium secretion parallels the plasma potassium concentration. Secretion of potassium in response to changes in acid-base balance (which affects plasma pH) is complex. In general, acute acidosis decreases secretion of potassium, whereas acute alkalosis increases secretion and loss of potassium from the body. Response to chronic acid-base disorders is varied.

Sodium, Chloride, and Potassium Imbalance

Acute excessive intakes do not normally result in retention of sodium, chloride, and potassium because of the capacity of the kidneys to excrete these ions. Retention occurs when kidney function is compromised. Dietary deficiency does not normally occur because normal consumption usually exceeds body needs.

Since the extracellular fluid volume changes in parallel with its sodium concentration, sodium retention in renal failure or congestive heart failure results in edema and possibly hypertension (Table 3). Excessive loss of sodium resulting in hypovolemia and hypotension can occur through diuresis, Addison's disease, severe vomiting, or diarrhea.

Changes in plasma concentration of potassium affects the excitability of nerves and muscle cells (Table 3). Retention of potassium causes hyperkalemia (plasma potassium concentration exceeding 5.0 mmol/l), and depletion causes hypokalemia (plasma potassium concentration less than 3.5 mmol/l). Retention of potassium occurs when there is a lack of aldosterone secretion, or a lack of responsiveness of the kidney to aldosterone. An important clinical manifestation of hyperkalemia is cardiac arrhythmia, which can lead to cardiac arrest. Depletion of potassium can occur through hyperaldosteronism, diuresis, vomiting, or diarrhea. Manifestations of hypokalemia include depressed neuromuscular functions and, in more severe hypokalemia, cardiac arrhythmias.

Table 3

Nutritional Considerations

Epidemiological and experimental evidence has implicated habitual high dietary salt consumption in the development of hypertension, but controversy remains regarding the importance of sodium salts in the regulation of blood pressure and the mechanisms by which salt influences blood pressure (Stamler, 1977). Intervention studies of dietary salt restrictions to lower blood pressure have produced mixed results. Nevertheless, various clinical trials indicate some beneficial effects of dietary restriction of sodium on blood pressure, and it may also decrease the incidence of stroke and ischemic heart disease.

High consumption of potassium, found in foods like oranges, apricots, and dates, on the other hand, appears to have a protective action against cardiovascular diseases, although the mechanism of action is not known. Epidemiological studies have demonstrated an inverse relationship of potassium intake with blood pressure, incidence of stroke, and other cardiovascular diseases (Young, Huabao, and McCabe). A direct relationship between blood pressure and the ratio of sodium to potassium in the urine has also been found (Stamler).

Repeated intake over a long period of salt from salted and smoked products is associated with atrophic gastritis and gastric cancer. However, experimental evidence indicates that salt alone is not carcinogenic; the high dietary salt content may enhance the initiation of cancer by facilitating the action of any carcinogen, such as polycyclic aromatic hydrocarbons, present in the diet (Cohen and Roe, 1977), or potentiating Helicobacter pylori–associated carcinogenesis (Fox et al., 1999).

Diarrhea

Daily, about 8 to 10 l of water and large amounts of ions enter the gastrointestinal tract; about 1 to 2 l are from the diet, the rest from secretions of the alimentary tract. The greater part of this fluid is absorbed by the intestinal cells so that only about 150 ml of fluid are lost daily in the stool of an adult. Stools contain a low content of sodium and chloride but a high content of potassium so that the daily losses averages 6 mmol for sodium, 12 mmol for potassium, 3 mmol for chloride, and 5 mmol for bicarbonate. Loss of this water and ions can increase greatly in diarrhea, and if extreme, several liters of fluid can be lost, leading to dehydration and electrolyte and acid-base disturbances.

Diarrhea is defined as an increase in stool liquidity and a fecal volume of more than 200 ml/day in adults. Clinically, the most common and important causes of diarrhea are osmotic and secretory. Ingestion of a poorly absorbable solute, such as magnesium sulfate, or malabsorption or maldigestion of a specific solute because of enzyme deficiencies, as seen in lactase deficiency, can cause osmotic diarrhea. The presence of these solutes increases the intestinal luminal osmolarity, causing water to be retained in the lumen.

Various viral and bacterial infections can cause secretory diarrhea. Enteroinvasive bacteria such as Shigella and Salmonella invade intestinal mucosa to produce ulceroinflammatory lesions resulting in a failure of normal absorption. On the other hand, bacteria such as Vibrio cholerae release toxins that increase secretion of sodium chloride and water. If the cholera is severe, up to 18 l of watery stools can be passed in a day. These stools contain ionic concentrations similar to that of plasma, so that large amounts of sodium, chloride, and potassium can be lost.

Dehydration caused by diarrhea ranges from mild to severe. The severity of dehydration can be assessed clinically by examining the patient for sunken eyeballs, skin turgor, mental status, blood pressure, and urine output. Fluid replacement is of utmost importance, especially in severe dehydration, to prevent circulatory collapse. Although diarrhea causes losses of sodium as well as potassium and bicarbonate, the immediate concern in treating severe diarrhea is to replace sodium and water to restore the circulatory volume. Dehydration in diarrhea can be reversed by oral or, in emergency, intravenous rehydration therapy.

The World Health Organization has recommended the use of oral rehydration therapy for treatment of mild to moderate cases of diarrhea. This program has been very successful in reducing mortality from diarrheal diseases, particularly in infants in developing countries. Oral rehydration fluid contains 3.5 g of sodium chloride, 2.5 g of sodium bicarbonate, 1.5 g of potassium chloride, and 20 g of glucose in 1 l of water. An alternative household remedy is to make a solution containing three "finger pinches" of salt, a "fistful of sugar" and one quart of water. Addition of sugar to the oral rehydration fluid helps to increase the absorption of sodium chloride through the sodium-glucose transporter system in the small intestine.

Thermoregulation Through Perspiration

Heat is produced continuously by the body during metabolism, and it is also taken up by the body from the environment by radiation and conduction. Heat is lost from the body by radiation, conduction and convection, and evaporation. Even in the absence of perspiration, water is lost continuously from the body by evaporation from the upper respiratory tract and by passive evaporation from the skin. These insensible water losses amount to a total of about 0.6 l/day, of which slightly more than 50 percent is from the skin. For every liter of water that evaporates from the body, 580 kcal (2428 kJ) of heat is dissipated. During intense physical exertion or at a high ambient temperature, loss of heat from radiation, conduction, and insensible water loss are insufficient to prevent a rise in body temperature. Under these circumstances, heat loss is enhanced by the production and evaporation of sweat. Loss of heat by evaporation of sweat is an effective means of removing excess heat from the body, and it can be controlled by regulating the rate of sweating. When the body temperature rises above 98.6°F (37°C), stimulation of the temperature-regulating center in the hypothalamus causes sweating.

Sweat is produced by sweat glands by actively secreting into ducts a fluid similar in composition to that of plasma. As this primary secretion passes along the ducts of the sweat glands to the surface of the skin, sodium and chloride are absorbed in excess of water, resulting in the production of a dilute fluid that has a lower content of sodium and chloride. Sodium chloride content in sweat varies; it depends on the rate of flow. For a young adult, the average value is about 50 mmol/l for sodium and 30 mmol/l for chloride. The transport mechanisms for sodium and chloride are affected in patients suffering from cystic fibrosis so that their concentrations in the sweat are increased. For the purpose of diagnosis, the upper limit of the normal values for children and young adults are set at 70–80 mmol/l for sodium and 60–70 mmol/l for chloride (Lentner, ed.).

Rate of sweat production depends on the ambient temperature and humidity, and the degree of activity of the individual. For a 70 kg man doing light work at an ambient temperature of 84°F (29°C), daily loss is about 2 to 3 l. An unacclimatized individual who is performing hard physical activity in a hot, humid environment may lose, for a short time, up to 2 to 4 l/hour of sweat. As the duration of perspiration increases, the rate of production decreases to about 0.5 l/hour. Therefore, even at maximal sweating, the rate of heat loss may not be rapid enough to dissipate the excess heat from the body. Dehydration from excessive loss of water and sodium chloride stimulates the thirst mechanism, and if water intake is not increased, it can cause weakness and, if severe, circulatory collapse.

Adaptation to heat leads to physiological changes that include an increase in sweat production, an increase in plasma volume, and a decrease in concentration of sodium and chloride in the sweat and urine. These latter two effects are caused by an increase in aldosterone secretion as a result of dehydration and loss of sodium from the body. The decrease in the concentration of sodium and chloride in sweat and urine allows for better conservation of these ions in the body. An unacclimatized person who sweats profusely often loses as much as 13 to 30 g of salt per day for the first few days, but after four to six weeks of acclimatization the loss can be as low as 3 to 5 g a day.

There is a limit at which the body can lose heat even when perspiring maximally. The progressive rise in body temperature will affect the heat-regulating ability of the hypothalamus, resulting in a decrease in sweating. Therefore, a high body temperature tends to perpetuate itself unless measures are taken specifically to decrease the body temperature. When the body temperature rises beyond a critical temperature of 106°F (41°C), the person is likely to develop heat stroke. Symptoms include dizziness, abdominal distress, delirium, and eventually loss of consciousness. Some of these symptoms are exacerbated by a mild degree of circulatory shock as a result of sodium loss and dehydration.

Bibliography

Cohen, A. J., and F. J. Roe. "Evaluation of the Aetiological Role of Dietary Salt Exposure in Gastric and Other Cancers in Humans." Food and Chemical Toxicology 35 (1997): 271–293.

Fox, James G., et al. "High Salt Diet Induces Gastric Epithelial Hyperplasia and Parietal Cell Loss, and Enhances Helicobacter pylori Colonization in C57BL/6 Mice." Cancer Research 59 (1999): 4823–4828.

Lentner, Cornelius, ed. Geigy Scientific Tables. 8th ed., vol. 1. Basel: Ciba-Geigy Limited, 1981.

National Research Council. Recommended Dietary Allowances. 10th ed. Washington, D. C.: National Academy Press, 1989.

Palmer, Biff F., Robert J. Alpern, and Donald W. Seldin. "Physiology and Pathophysiology of Sodium Retention." In The Kidney: Physiology and Pathophysiology, edited by Donald W. Seldin and Gerhard Giebisch. 3d ed., Philadelphia: Lippincott Williams and Wilkins, 2000. Vol II, Chapter 54, pp. 1473–1517.

Rodriguez-Soriano, Juan. "Potassium Homeostasis and Its Disturbance in Children." Pediatric Nephrology 9 (1995): 364–374.

Stamler, Jeremiah. "The INTERSALT Study: Background, Methods, Findings, and Implications." American Journal of Clinical Nutrition 65 (1997): 626S–642S.

Toto, Robert D., and Donald W. Seldin. "Salt Wastage." In The Kidney: Physiology and Pathophysiology, edited by Donald W. Seldin and Gerhard Giebisch. vol. 2, 3d ed., pp. 1519–1536. Philadelphia: Lippincott Williams and Wilkins, 2000.

Young, David B., Huabao Lin, and Richard D. McCabe. "Potassium's Cardiovascular Protective Mechanisms." American Journal of Physiology 268 (1995): R825–R837.

—Hwai-Ping Sheng

A substance that can serve as a conductor for an electric current when it is dissolved in a solution. Electrolytes are found in the blood and tissue fluids of the body.

A chemical substance which, when dissolved in water or melted, dissociates into electrically charged particles (ions), and thus is capable of conducting an electric current. The principal positively charged ions in the body fluids (cations) are sodium (Na+), potassium (K+), calcium (Ca²+), and magnesium (Mg²+). The most important negatively charged ions (anions) are chloride (Cl⁻), bicarbonate (HCO³−), and phosphate (PO₄³−). These electrolytes are involved in metabolic activities and are essential to the normal function of all cells. Concentration gradients of sodium and potassium across the cell membrane produce the membrane potential and provide the means by which electrochemical impulses are transmitted in nerve and muscle fibers.
The concentration of the various electrolytes in body fluids is maintained within a narrow range. However, the optimal concentrations differ in the extracellular fluid and intracellular fluid. An electrolyte imbalance exists when the serum concentration of an electrolyte is either too high or too low.
Stability of the electrolyte balance depends on adequate intake of water and the electrolytes, and on homeostatic mechanisms within the body that regulate the absorption, distribution and excretion of water and its dissolved particles.
The effects of an electrolyte imbalance are not isolated to a particular organ or system. In general, however, imbalances in calcium concentrations affect the bones, kidney and gastrointestinal tract. Calcium also influences the permeability of cell membranes and thereby regulates neuromuscular activity. sodium affects the osmolality of blood and therefore influences blood volume and pressure and the retention or loss of interstitial fluid. potassium affects muscular activities, notably those of the heart, intestines and respiratory tract, and also affects neural stimulation of the skeletal muscles.

• e. clearance ratio — see fractional excretion tests.
• e. disturbances — include hyper- and hypo-potassemia, natremia, phosphatemia, calcemia, chloremia.
• e. fluid balance — balance between fluid and electrolytes.
• e. homeostasis — maintenance of the osmotic pressure of the blood and tissue fluids by the maintenance of a proper balance between the normal electrolytes in the fluid, and at the same time maintaining adequate concentrations of calcium and magnesium and the proper acid–base balance.
• e. solution therapy — see fluid therapy.

Electrically conducting liquid (wet) or paste (dry)

This article is about the ionic solution. For the R.E.M. song, see Electrolite.

In chemistry, an electrolyte is any substance containing free ions that make the substance electrically conductive. The most typical electrolyte is an ionic solution, but molten electrolytes and solid electrolytes are also possible.

Contents 1 Principles 2 Physiological importance 2.1 Measurement 2.2 Sports drinks 3 Electrochemistry 4 Dry electrolyte 5 See also 6 References

Principles

Electrolytes commonly exist as solutions of acids, bases or salts. Furthermore, some gases may act as electrolytes under conditions of high temperature or low pressure. Electrolyte solutions can also result from the dissolution of some biological (e.g., DNA, polypeptides) and synthetic polymers (e.g., polystyrene sulfonate), termed polyelectrolytes, which contain charged functional group.

Electrolyte solutions are normally formed when a salt is placed into a solvent such as water and the individual components dissociate due to the thermodynamic interactions between solvent and solute molecules, in a process called solvation. For example, when table salt, NaCl, is placed in water, the salt (a solid) dissolves into its component elements, according to the dissociation reaction

NaCl_(s) → Na⁺_(aq) + Cl⁻_(aq).

It is also possible for substances to react with water when they are added to it, producing ions, e.g., carbon dioxide gas dissolves in water to produce a solution which contains hydronium, carbonate, and hydrogen carbonate ions.

Note that molten salts can be electrolytes as well. For instance, when sodium chloride is molten, the liquid conducts electricity.

An electrolyte in a solution may be described as concentrated if it has a high concentration of ions, or dilute if it has a low concentration. If a high proportion of the solute dissociates to form free ions, the electrolyte is strong; if most of the solute does not dissociate, the electrolyte is weak. The properties of electrolytes may be exploited using electrolysis to extract constituent elements and compounds contained within the solution.

Physiological importance

In physiology, the primary ions of electrolytes are sodium(Na⁺), potassium (K⁺), calcium (Ca²⁺), magnesium (Mg²⁺), chloride (Cl⁻), hydrogen phosphate (HPO₄²⁻), and hydrogen carbonate (HCO₃⁻). The electric charge symbols of plus (+) and minus (−) indicate that the substance in question is ionic in nature and has an imbalanced distribution of electrons, which is the result of chemical dissociation.

All known higher lifeforms require a subtle and complex electrolyte balance between the intracellular and extracellular milieu. In particular, the maintenance of precise osmotic gradients of electrolytes is important. Such gradients affect and regulate the hydration of the body, blood pH, and are critical for nerve and muscle function. Various mechanisms exist in living species that keep the concentrations of different electrolytes under tight control.

Both muscle tissue and neurons are considered electric tissues of the body. Muscles and neurons are activated by electrolyte activity between the extracellular fluid or interstitial fluid, and intracellular fluid. Electrolytes may enter or leave the cell membrane through specialized protein structures embedded in the plasma membrane called ion channels. For example, muscle contraction is dependent upon the presence of calcium (Ca²⁺), sodium (Na⁺), and potassium (K⁺). Without sufficient levels of these key electrolytes, muscle weakness or severe muscle contractions may occur.

Electrolyte balance is maintained by oral, or in emergencies, intravenous (IV) intake of electrolyte-containing substances, and is regulated by hormones, generally with the kidneys flushing out excess levels. In humans, electrolyte homeostasis is regulated by hormones such as antidiuretic hormone, aldosterone and parathyroid hormone. Serious electrolyte disturbances, such as dehydration and overhydration, may lead to cardiac and neurological complications and, unless they are rapidly resolved, will result in a medical emergency.

Measurement

Measurement of electrolytes is a commonly performed diagnostic procedure, performed via blood testing with ion selective electrodes or urinalysis by medical technologists. The interpretation of these values is somewhat meaningless without analysis of the clinical history and is often impossible without parallel measurement of renal function. Electrolytes measured most often are sodium and potassium. Chloride levels are rarely measured except for arterial blood gas interpretation since they are inherently linked to sodium levels. One important test conducted on urine is the specific gravity test to determine the occurrence of electrolyte imbalance.

Sports drinks

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Electrolytes are commonly found in sports drinks. In oral rehydration therapy, electrolyte drinks containing sodium and potassium salts replenish the body's water and electrolyte levels after dehydration caused by exercise, diaphoresis, diarrhea, vomiting, intoxication or starvation. Athletes exercising in extreme conditions (for three or more hours continuously e.g. marathon or triathlon) who do not consume electrolytes, risk dehydration (or hyponatremia)^[1].

The regular and frequent use of sports drinks by men and women can potentially lead to increased dental decay and erosion. ^[2]

A simple electrolyte drink can be home-made by using the correct proportions of water, sugar, salt, salt substitute for potassium, and baking soda.^[3] However, effective electrolyte replacements should include all electrolytes required by the body, including sodium chloride, potassium, magnesium, and calcium that can be either obtained in a sports drink or a solid electrolyte capsule.^[4]

Electrochemistry

Main article: electrolysis

When electrodes are placed in an electrolyte and a voltage is applied, the electrolyte will conduct electricity. Lone electrons normally cannot pass through the electrolyte; instead, a chemical reaction occurs at the cathode consuming electrons from the anode, and another reaction occurs at the anode producing electrons to be taken up by the cathode. As a result, a negative charge cloud develops in the electrolyte around the cathode, and a positive charge develops around the anode. The ions in the electrolyte move to neutralize these charges so that the reactions can continue and the electrons can keep flowing.

For example, in a solution of ordinary salt (sodium chloride, NaCl) in water, the cathode reaction will be

2H₂O + 2e⁻ → 2OH⁻ + H₂

and hydrogen gas will bubble up; the anode reaction is

2H₂O → O₂ + 4H⁺ + 4e⁻

and oxygen gas will be liberated. The positively charged sodium ions Na⁺ will react towards the cathode neutralizing the negative charge of OH⁻ there, and the negatively charged chlorine ions Cl⁻ will react towards the anode neutralizing the positive charge of H⁺ there. Without the ions from the electrolyte, the charges around the electrode would slow down continued electron flow; diffusion of H⁺ and OH⁻ through water to the other electrode takes longer than movement of the much more prevalent salt ions.

In other systems, the electrode reactions can involve the metals of the electrodes as well as the ions of the electrolyte.

Electrolytic conductors are used in electronic devices where the chemical reaction at a metal/electrolyte interface yields useful effects.

• In batteries, two metals with different electron affinities are used as electrodes; electrons flow from one electrode to the other outside of the battery, while inside the battery the circuit is closed by the electrolyte's ions. Here the electrode reactions convert chemical energy to electrical energy.
• In some fuel cells, a solid electrolyte or proton conductor connects the plates electrically while keeping the hydrogen and oxygen fuel gases separated.
• In electroplating tanks, the electrolyte simultaneously deposits metal onto the object to be plated, and electrically connects that object in the circuit.
• In operation-hours gauges, two thin columns of mercury are separated by a small electrolyte-filled gap, and, as charge is passed through the device, the metal dissolves on one side and plates out on the other, causing the visible gap to slowly move along.
• In electrolytic capacitors the chemical effect is used to produce an extremely thin 'dielectric' or insulating coating, while the electrolyte layer behaves as one capacitor plate.
• In some hygrometers the humidity of air is sensed by measuring the conductivity of a nearly dry electrolyte.
• Hot, softened glass is an electrolytic conductor, and some glass manufacturers keep the glass molten by passing a large current through it.

Dry electrolyte

Dry electrolytes are essentially gels in a flexible lattice framework.^[5]

See also

• Strong electrolyte
• ITIES (Interface between Two Immiscible Electrolyte Solutions)

References

This article needs additional citations for verification. Please help improve this article by adding reliable references. Unsourced material may be challenged and removed. (October 2008)

1. ^ Template:Cite jornal
2. ^ "Sports drinks hazard to teeth". British Journal of Sports Medicine 31: 28-30. August 2006. http://bjsportmed.com/cgi/content/abstract/31/1/28. 
3. ^ http://www.webmd.com/hw/health_guide_atoz/str2254.asp?navbar=hw86827
4. ^ http://www.runnersweb.com/running/rw_news_frameset.html?http://www.runnersweb.com/running/news/rw_news_20060612_ERB_Electrolytes.html
5. ^ http://www.evworld.com/article.cfm?storyid=933

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Dansk (Danish)
n. - elektrolyt, akkumulatorvæske

Nederlands (Dutch)
elektrolyt (soort elektrische geleider)

Français (French)
n. - électrolyte

Deutsch (German)
n. - Elektrolyt (durch Strom zersetzbarer Stoff)

Ελληνική (Greek)
n. - (φυσ.) ηλεκτρολύτης

Italiano (Italian)
elettrolito

Português (Portuguese)
n. - eletrólito (m) (Quím.) (Fís.)

Русский (Russian)
электролит

Español (Spanish)
n. - electrólito

Svenska (Swedish)
n. - elektrolyt

中文（简体）(Chinese (Simplified))
电解物, 电解液, 电解质

中文（繁體）(Chinese (Traditional))
n. - 電解物, 電解液, 電解質

한국어 (Korean)
n. - 전해물

日本語 (Japanese)
n. - 電解液, 電解質

العربيه (Arabic)
‏(الاسم) الالكتروليت ( المنحل بالكهرباء)‏

עברית (Hebrew)
n. - ‮אלקטרוליט, נוזל הניתן לפירוק באמצעות זרם חשמלי, בייחוד נוזל בסוללה‬

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