Anne

  • November 2019
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Definition: Electrical conductivity is the measure of total concentration of dissolved salts in water. When salts dissolve in water, they give off electrically charged ions that conduct electricity. The more ions in the water, the greater the electrical conductivity it has. Because there are almost no ions in distilled water, it has almost no electrical conductivity. Hard water contains more salts, and therefore more ions, has a high electrical conductivity. Problems With Electrolyte Balance The level of any electrolyte in the blood can become too high or too low. The main electrolytes in the blood are sodium, potassium, calcium, magnesium, chloride, phosphate, and carbonate. Most commonly, problems occur when the level of sodium, potassium, or calcium is abnormal. Often, electrolyte levels change when water levels in the body change. Doctors refer to a low electrolyte level with the prefix "hypo-" and to a high level with the prefix "hyper-." The prefix is combined with the scientific name of the electrolyte. For example, a low level of potassium is called hypokalemia, and a high level of sodium is called hypernatremia. Older people are more likely to develop abnormalities in electrolyte levels for the same reasons that they are more likely to become dehydrated or overhydrated. The main reason is that as the body ages, the kidneys function less well. The use of certain drugs, including diuretics and some laxatives, can increase the risk of developing electrolyte abnormalities. Problems with walking can increase the risk of developing electrolyte abnormalities because getting fluids and food may be difficult. Many chronic disorders (such as Paget's disease) and any disorder that causes fever, vomiting, or diarrhea can result in electrolyte abnormalities. Electrolyte abnormalities can be diagnosed by measuring electrolyte levels in a sample of blood or urine. Other tests may be needed to determine the cause of the abnormalities. To treat a low level of some electrolytes, such as sodium or potassium, doctors usually advise eating foods rich in the electrolyte or taking supplements. If the level is very low, the electrolyte may be given through a tube inserted in a vein (intravenously). If the level is high, treatment consists of consuming more fluids. Sometimes fluids must be given intravenously. Sometimes treatment is more complex because the disorder causing the electrolyte abnormality must be treated. Sodium Hyponatremia: A low sodium level (hyponatremia) may result from not consuming enough sodium in the diet, excreting too much (in sweat or urine), or being overhydrated. The sodium level may decrease when a person drinks a lot of water without consuming enough salt (sodium chloride), typically during hot weather when a person also sweats more. The sodium level may decrease when large amounts of fluids that do not contain enough sodium are given intravenously. Diuretics help the kidneys excrete excess sodium and excess water. However, diuretics may cause the kidneys to excrete more sodium than water, resulting in a low sodium level. A low sodium level (and overhydration) can result when the body produces too much antidiuretic hormone, which signals the kidneys to retain water. Overproduction of this hormone can be caused by disorders such as pneumonia and stroke and by drugs, including anticonvulsants (such as carbamazepine) and a type of antidepressant called selective serotonin reuptake inhibitors (SSRIs—such as sertraline). Other disorders that can cause a low sodium level include poorly controlled diabetes, heart failure, liver failure, and kidney disorders.Having a low sodium level can cause confusion, drowsiness, muscle weakness, and seizures. A rapid fall in the sodium level often causes more severe symptoms than a slow fall. A low sodium level is restored to a normal level by gradually and steadily giving sodium and water intravenously. Hypernatremia: A high sodium level (hypernatremia) is usually caused by dehydration or use of diuretics. (Diuretics may also cause the kidneys to excrete more water than sodium.) Typically, thirst is the first symptom. A person with a high sodium level may become weak and feel sluggish. A very high sodium level can cause confusion, paralysis, coma, and seizures. If the sodium level is slightly high, it can be lowered by drinking fluids. If the sodium level is very high, fluids are given intravenously. Once the body's fluids are replaced, the high level of sodium returns to a normal level. Potassium Hypokalemia: A low potassium level (hypokalemia) is often caused by use of a diuretic. Many diuretics cause the kidneys to excrete more potassium (as well as more water) in urine. A low potassium level can also result from having diarrhea or vomiting for a long time. A slight decrease in the potassium level rarely produces symptoms. If the potassium level remains low for a long time, the body tends to produce less insulin. As a result, the level of sugar in the blood may increase. If the potassium level becomes very low, fatigue, confusion, and muscle weakness and cramps typically occur. A very low potassium level can cause paralysis and abnormal heart

rhythms (arrhythmias). For people who take digoxin (used to treat heart failure), abnormal heart rhythms tend to develop when the potassium level is even moderately low. Treatment involves taking potassium supplements by mouth as a tablet or liquid or eating foods rich in potassium. People who are taking a diuretic that causes potassium to be excreted are sometimes also given another type of diuretic, which reduces the amount of potassium excreted (potassium-sparing diuretic). Hyperkalemia: A high potassium level (hyperkalemia) is much more dangerous than a low potassium level. Most commonly, the cause is kidney failure or use of drugs that reduce the amount of potassium excreted by the kidneys. These drugs include the diuretic spironolactone and angiotensin-converting enzyme (ACE) inhibitors (used to lower blood pressure). When a person who takes one of these drugs also eats potassium-rich foods or takes a potassium supplement, the kidneys cannot always excrete the potassium. In such cases, the potassium level in the blood can increase rapidly. The first symptom of a high potassium level may be an abnormal heart rhythm. When doctors suspect a high potassium level, electrocardiography (ECG) may help with the diagnosis. This procedure can detect changes in the heart's rhythm that occur when the potassium level is high. People with a high potassium level must stop eating potassium-rich foods and stop taking potassium supplements. They may be given drugs that cause the body to excrete excess potassium, such as diuretics. If the potassium level is very high or is increasing, treatment must be started immediately. If the heart rhythm is abnormal, calcium is given intravenously. This treatment helps protect the heart. Then diuretics or drugs that prevent potassium from being absorbed are given to reduce the amount of potassium in the body. These drugs may be given intravenously, taken by mouth, or given as enemas. Calcium Hypocalcemia: A low calcium level (hypocalcemia) can result when a disorder such as a widespread infection in blood and other tissues (sepsis) develops suddenly. A low calcium level can also result when the body produces less parathyroid hormone, as may occur if the parathyroid glands are removed or damaged during neck surgery. A low level can also result from a deficiency of vitamin D. Vitamin D helps the body absorb calcium from foods. People may develop a vitamin D deficiency when they do not eat enough foods that contain vitamin D or when they do not spend much time outside. (Vitamin D is formed when the skin is exposed to direct sunlight.) Certain drugs, such as the anticonvulsants phenytoin and phenobarbital, can interfere with the processing of vitamin D, resulting in a deficiency of vitamin D. Several disorders, such as an underactive thyroid gland (hypothyroidism) and pancreatitis, can result in a low calcium level. A low calcium level makes a person weak and causes numbness in the hands or feet. It can cause confusion or seizures. Treatment involves taking calcium supplements by mouth. If a disorder is the cause, it should be treated. Hypercalcemia: A high calcium level (hypercalcemia) can result when bone is broken down and releases calcium into the bloodstream. Calcium may be released when cancer spreads to the bone or when Paget's disease (a bone disorder) becomes so severe that it makes a person unable to move around. Normally, parathyroid hormone helps the body control the level of calcium in blood. An abnormally high level of parathyroid hormone can result in a high calcium level. Usually, the cause is production of an excessive amount of hormone by a tumor in the parathyroid gland. But some cancers, including certain lung cancers, can also produce parathyroid hormone. A high calcium level can also result when the level of thyroid hormone is abnormally high. A slight increase in the calcium level may not cause any symptoms. A very high level can result in dehydration because it causes the kidneys to excrete more water. A very high level can also cause loss of appetite, nausea, vomiting, and confusion. A person may even go into a coma and die. If the calcium level is very high, rapid treatment is needed. Giving fluids intravenously helps. Often, drugs such as calcitonin and bisphosphonates must be given intravenously for short periods of time. These drugs decrease the amount of bone being broken down and thus the amount of calcium released into the bloodstream. Other treatments may be needed, depending on the cause of the high calcium level. When the cause is cancer or Paget's disease, bisphosphonates are often taken by mouth indefinitely. When the cause is a tumor in the parathyroid gland, surgery to remove the tumor or part of the parathyroid gland may be done. Introduction

Water is the main component of blood and cells. It fills most of the spaces around cells. To function normally, the body must keep the amount of water in these areas in balance and relatively constant. Too little water (dehydration) or too much water (overhydration) in the body can cause problems. The water in the body contains dissolved minerals called electrolytes. They include sodium, potassium, and calcium. The body must also keep levels of electrolytes in balance and relatively constant. The balance of electrolytes is closely tied to the balance of water in the body: If one changes, the other usually also changes. To maintain water and electrolyte balance, the body must replace water and electrolytes that are lost as the body performs its necessary functions. The body loses water and electrolytes primarily in urine, produced by the kidneys. Water and electrolytes are also lost in sweat, feces, and air that is breathed out. The body obtains water and electrolytes primarily from beverages and foods consumed. A healthy body can adjust the amount of water and electrolytes lost and consumed. Thirst, hunger, and the kidneys help with these adjustments. For example, a person who feels thirsty usually drinks more fluids. When a person becomes dehydrated, the brain releases a hormone called antidiuretic hormone. This hormone signals the kidneys to retain more water by making and excreting less urine. As the body ages, it changes in ways that make older people more likely to have problems with water and electrolyte balance. The older body contains less water. Water accounts for 60% of body weight in healthy young people but for only 45% in healthy older people. In older people, the kidneys are less able to regulate the excretion of water and to concentrate urine as needed. Therefore, more water may be lost in urine. Also, older people often do not drink enough water, especially on hot days, partly because they tend to be less thirsty. If older people have problems with walking, they may not be able to get themselves enough water to drink. Older people who have urinary incontinence may drink less because they are worried about getting to a bathroom in time. Many disorders, especially those that cause fever, vomiting, or diarrhea, can result in problems with water and electrolyte balance. These disorders may be short-lived (for example, pneumonia) or chronic (for example, kidney failure). Many drugs, especially diuretics, can also cause problems.

Dehydration Dehydration is not having enough water in the body. Sometimes people dismiss dehydration as a minor nuisance. However, without treatment, dehydration can have serious effects, including confusion (delirium), dizziness, falls, and death. When a person is dehydrated, blood pressure falls, the body's organs do not receive enough blood and nutrients, and the body cannot cool itself adequately. Also, the levels of many electrolytes tend to become abnormal. The body tries to keep blood pressure from falling by moving water from cells and the spaces around the cells into the blood vessels. Then, the tissues dry out. The kidneys try to conserve water by concentrating urine more or by not making any urine. Dehydration can occur at any age. But older people are prone to dehydration because of changes that occur as the body ages—for example, older people sense thirst less quickly and intensely, and the kidneys function less well. Other conditions that make dehydration more likely include the following:



Hot weather, because sweating is increased



Fever, because sweating is increased and breathing becomes more rapid (causing more water to be lost in the air that is breathed out)



Diarrhea, because water is lost in the stool



Vomiting, because water is lost in the vomit



Diabetes that is poorly controlled, because the body produces more urine



Kidney disorders, because the kidneys are less able to concentrate urine as needed



Problems with walking, because getting water is difficult



Dementia, because the sense of thirst is reduced and the ability to get water when needed is impaired



Use of diuretics, because these drugs increase the amount of water (and salt) excreted by the kidneys

Symptoms and Diagnosis When dehydration is mild, the skin and the membranes of the nose and eyes become dry. A dehydrated person may feel confused and sluggish. After standing up, the person may feel light-headed and may faint. As dehydration becomes more severe, the body makes less urine, and the urine becomes dark. Severe dehydration can lead to a fall in blood pressure that can be life threatening.

Blood and urine tests help doctors diagnose dehydration and determine how severe it is. Doctors measure levels of certain electrolytes and other substances that indicate how well the kidneys are functioning. Treatment Treatment involves replacing lost fluids. How rapidly they are replaced depends on how severe dehydration is. People who have mild dehydration are usually given about 2 to 3 liters of water to drink over a period of a few hours. People who have moderate dehydration are usually given a fluid that contains some salt (sodium) and other electrolytes. Dilute broths and rehydration formulas (available in pharmacies without a prescription) are a good choice. Some people must be given fluids through a tube inserted in a vein (intravenously). Such people include those who are severely dehydrated, those who cannot swallow, and those who are in a coma. If electrolytes must also be replaced, they are given intravenously with the fluids.

Overhydration Overhydration is having too much water in the body. When more fluid is consumed than can be excreted, overhydration occurs. The blood vessels overfill, and fluid moves from the blood vessels into the spaces around cells, causing swelling (edema). Overhydration has many causes. The most common is heart failure, which occurs when the heart cannot pump blood adequately. Kidney disorders can cause overhydration if the kidneys cannot excrete enough water. Overhydration can also occur when the body produces too much antidiuretic hormone (which signals the kidneys to retain more water). Overproduction of antidiuretic hormone may be caused by disorders such as pneumonia and stroke and by drugs such as carbamazepine (an anticonvulsant) and sertraline (an antidepressant). Some drugs, especially nonsteroidal anti-inflammatory drugs (NSAIDs), and foods that are high in sodium cause fluids to be retained and may lead to mild overhydration. People who are hospitalized can become overhydrated if they are given intravenous fluids or blood transfusions too rapidly. Symptoms and Diagnosis Overhydration often causes swelling in the legs or, if people are confined to bed, in the lower back. However, swelling in the legs is not always caused by overhydration. Often, it is caused or worsened by poor circulation due to a blood vessel disorder (such as chronic venous insufficiency), particularly in people who sit a lot. Overhydration can cause shortness of breath because fluid backs up in the lungs. Often, shortness of breath is worse when a person lies down, because fluid moves from the feet and legs into the abdomen and chest. The person may wake up shortly after lying down, gasping for air. If overhydration is suspected, a doctor looks for swelling and enlargement of organs, such as the heart and liver. The veins in the neck are examined to see whether they are overfilled. With a stethoscope, the doctor listens to the heart and lungs for any signs of heart failure. Other tests may be done to determine whether symptoms are due to overhydration or to poor circulation in the legs. Blood tests may be done to measure levels of electrolytes or other substances that indicate how well the kidneys are functioning. A chest x-ray can show the backup of fluid in the lungs. Tests may be needed to determine whether heart failure is present. Treatment For people who are overhydrated, treatment involves helping the body excrete the excess water. Diuretics are drugs that help the kidneys do just that. There are several types of diuretics. Thiazide diuretics are often used first, because they are mild and tend to have few side effects. However, more potent diuretics, such as furosemide, are often needed. Diuretics can be taken by mouth or given intravenously. Most diuretics cause the kidneys to excrete more potassium as well as more water. Therefore, most people who take diuretics have to take potassium supplements or eat foods rich in potassium. Some people are also given another type of diuretic, which reduces the amount of potassium excreted (potassium-sparing diuretic).

Taking a diuretic can cause or worsen urinary incontinence. Taking a diuretic can also worsen the need to urinate during the night (nocturia). However, a dose of a diuretic can usually be timed so that the diuretic's maximum effect does not occur when a bathroom is unavailable or when a person is sleeping. If edema due to overhydration is bothersome, support stockings can help reduce the amount of fluid that accumulates in the legs. Consuming less salt also helps. If edema is due to poor circulation rather than overhydration, increasing physical activity can help. Usually, the blood vessel disorder that is causing poor circulation is treated. If possible, the cause of overhydration is corrected. If the cause was giving intravenous fluids too rapidly, doctors give them more slowly. Heart failure and kidney disorders can be treated. If the cause is a drug, the drug may be discontinued. However, some older people need to take NSAIDs for arthritis or pain. Such people may have to tolerate a small amount of edema or take a diuretic. If the cause of overhydration is overproduction of antidiuretic hormone, the amount of fluids consumed each day may have to be limited. Fluid and Electrolyte Balance Electrolytes are minerals in your body that have an electric charge. They are in your blood, urine and body fluids. Maintaining the right balance of electrolytes helps your body's blood chemistry, muscle action and other processes. Sodium, calcium, potassium, chlorine, phosphate and magnesium are all electrolytes. You get them from the foods you eat and the fluids you drink. Levels of electrolytes in your body can become too low or too high. That can happen when the amount of water in your body changes. Causes include some medicines, vomiting, diarrhea, sweating or kidney problems. Problems most often occur with levels of sodium, potassium or calcium. It is important to keep a balance of electrolytes in your body, because they affect the amount of water in your body, blood acidity (pH), muscle action, and other important processes. You lose electrolytes when you sweat, and you must replace them by drinking fluids. Electrolytes exist in the blood as acids, bases, and salts (such as sodium, calcium, potassium, chlorine, magnesium, and bicarbonate). They can be measured by laboratory studies of the blood. Update Date: 8/14/2007 Electrolytes are minerals in your blood and other body fluids that carry an electric charge. See also: = When wires connected to a battery and light bulb are placed into granular sodium chloride, the bulb does not light. It does not conduct. = When wires connected to a battery and light bulb are placed into granular sugar, the light bulb does not light. Solid sugar does not conduct electricity. =When wires connected to a battery and light bulb touch granular zinc, the bulb lights brightly. Metallic zinc conducts electricity. =When a sample of wax touches wires connected to a battery and light bulb, the bulb does not light. Wax is not a conductor. =When a sodium chloride crystal touches wires connected to a battery and light bulb, the bulb does not light. It is not a conductor. =When wires connected to a light bulb and battery are placed into sugar water, the light bulb does not light. Sugar is a non electrolyte. =Aqueous sodium chloride lights the bulb brightly. Sodium chloride is a strong electrolyte. =Aqueous hydrochloric acid lights the bulb brightly. Hydrochloric acid is a strong electrolyte. Solution conductivity Electrons are not the only particles capable of carrying an electric current. Ions can do it, too. An ion is an atom or group of atoms with an electric charge. Suppose you dissolve a crystal of table salt (sodium chloride) in water. Salt crystals consist of positive sodium ions and negative chloride ions. In the solid state, these ions are not free to move around. Once they are dissolved in water, however, they become completely mobile. They are free to "swim" about in the water and to respond to an electric current from a battery. That current supplies electrons that cause positive sodium ions to flow in one direction and negative chloride ions to flow in the opposite direction. A good example of this effect can be seen in the conductivity of water. Pure water consists only of water molecules. The electrons in water molecules are held tightly by hydrogen and oxygen atoms and are not free to move. Attaching a battery to a container of water produces no electric current because pure water is an insulator. But a few grains of table salt added to the water changes things completely. Sodium ions and chloride ions are released from the salt, and the salt water solution becomes conductive.

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