Fluid and electrolyte disorders are abnormalities in the distribution of water and ions * in the body that result in health problems.
Electrolytes are charged particles (ions) that form when certain compounds are dissolved in water. Positively charged ions are called cations. Negatively charged ions are called anions. Some of the electrolytes that are important to maintaining health are sodium, potassium, calcium, magnesium, chloride, phosphate, bicarbonate, and sulfate.
Fluids and electrolytes are not evenly distributed in the body. About two-thirds of the fluid in the body is found inside cells and is called intracellular fluid. The remaining one-third is found in the spaces between cells, in the circulatory system, and in smaller amounts in the stomach, bladder, and a few other places. This fluid is called extracellular fluid. The distribution of fluid in the body is closely related to the distribution of electrolytes, particularly sodium and potassium. To understand this connection, it is necessary to understand what causes water to move in and out of cells.
Water follows electrolytes. Water passes easily across cell membranes. When fluid with two different concentrations of electrolytes is separated by a cell membrane, there is pressure (called osmotic pressure) for water to flow across the membrane from fluid that contains fewer electrolytes (less concentrated) into fluid that contains more electrolytes (more concentrated). If osmotic pressure were the only factor affecting the movement of water, water and electrolytes would be evenly distributed inside and outside of cells. However, chemical reactions in the cell membrane actively prevent this from happening. Different types of cells have membranes that allow some electrolytes to pass across them while blocking others. The cell uses energy to drive this selection process and to maintain different concentrations of electrolytes on either side of the membrane.
The concentration of electrolytes in the body is highly dependent on how much water is in the body. The kidneys are the main regulators of body fluids. As blood passes through the kidneys, water, electrolytes, glucose (sugar), and wastes are filtered out of the blood into many tiny collecting tubules. If there is too little water in the body, the pituitary * secretes a hormone * called antidiuretic hormone (ADH). ADH signals the cells of the collecting tubules to allow water to pass back into the blood. If there is too much water in the body, little or no ADH is secreted, and instead of water returning to the blood, it is removed from the body in urine * . Other hormones help the kidneys to regulate the amount of electrolytes that are returned to the blood. The filtering process helps rebalance the level of fluids and electrolytes in the body and maintain them within the narrow range needed for the body to function properly.
When the body is functioning correctly, it is able to perform the complex regulatory events that keep conditions within the body stable despite variations in the amount of food and water a person consumes. When there is an imbalance in electrolytes, many systems in the body are affected, and serious, even fatal, health problems can result.
Dehydration is the most common cause of a fluid and electrolyte imbalance. Dehydration occurs when more water is lost from the body than is taken in through food and drink. This condition is often temporary; however, a 20 percent loss of water can be fatal. The average adult man loses about 10 cups (2.5 L) of water daily through urine, bowel movements, sweating, and breathing out water vapor from the lungs, but many conditions increase the amount of water lost. The following are some examples:
A great many diseases can upset the balance of electrolytes and thus the functioning of the body. Often more than one electrolyte is affected. These diseases include the following:
Some medications selectively increase the excretion of certain electrolytes, cause the body to retain excess water, or stimulate the kidneys to produce excess urine. Diuretic drugs (water pills) are the most widely used drugs to affect fluid and electrolyte balance. These drugs rid the body of water, but at the same time, they often cause excess loss of electrolytes (most often potassium) in the urine. By contrast, corticosteroid * drugs generally cause fluid retention (edema). Many chemotherapy * drugs also affect fluid and electrolyte balance, as do some herbal supplements.
Fluid and electrolyte imbalances may present with certain symptoms, including abnormal blood pressure, rapid pulse, abnormal breathing, and abnormal skin appearance, but none of these symptoms is specific to an electrolyte disorder. The definitive way of diagnosing an electrolyte imbalance is with urinalysis and blood tests. An electrolyte panel is a standard blood test that measures the concentrations of major electrolytes found in blood serum.
Treatment of dehydration involves replacement of fluids either intravenously * or by mouth with a fluid that contains a balance of electrolytes similar to that found in a healthy body. In mild cases of dehydration, young children can be given replacement pediatric rehydration fluids (e.g., Pedialyte), which are available at supermarkets and pharmacies without a prescription. Athletes frequently treat or prevent dehydration by using sports drinks that are formulated to replace electrolytes lost through sweating.
When the fluid and electrolyte imbalance is caused by an underlying disease, such as food poisoning that causes severe diarrhea, kidney failure, or an endocrine disease, that disease is treated. People with severe diarrhea and vomiting, cancer patients, people with hormonal imbalances, and other very ill people often need short-term fluid and electrolyte replacement therapy. Untreated electrolyte imbalances can cause health problems that range from chronic to rapidly fatal.
See also Diabetes • Kidney Disease
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* ions are positively or negatively charged elements or compounds, such as hydrogen, sodium, potassium, and phosphate, which are necessary for cellular metabolism.
* pituitary (pih-TOO-ih-tare-e) is a small oval-shaped gland at the base of the skull that produces several hormones—substances that affect various body functions, including growth.
* hormone is a chemical substance that is produced by a gland and sent into the bloodstream carrying messages that have specific effects on other parts of the body.
* urine is the liquid waste material secreted by the kidneys and removed from the body through the urinary tract.
* anorexia nervosa (an-o-REKse-a ner-VO-sa) is an emotional disorder characterized by dread of gaining weight, leading to self-starvation and dangerous loss of weight and malnutrition.
* bulimia (bu-LEE-me-a) is an eating disorder in which a person has episodes of out-of-control overeating, or binges, and then tries to make up for them by making themselves vomit, by taking laxatives, or by exercising to excess to avoid gaining weight.
* endocrine system is a system of ductless glands, including the thyroid and pituitary among others, that secrete hormones and control many bodily functions.
* adrenal glands (a-DREEN-al glands) are the pair of endocrine organs located near the kidneys.
* corticosteroid (KOR-ti-ko-STERoid) is one of several medications that are prescribed to reduce inflammation and sometimes to suppress the body's immune response.
* chemotherapy (KEE-mo-THER-apee) is the treatment of cancer with powerful drugs that kill cancer cells.
* intravenous (in-tra-VEE-nus), or IV, means within or through a vein. For example, medications, fluid, or other substances can be given through a needle or soft tube inserted through the skin's surface directly into a vein.