 |
 |
 |
|
Hyponatremia is a lower-than-normal concentration of sodium in the blood. Sodium is an electrolyte that helps with nerve and muscle function, and also helps to maintain blood pressure.
About 40% of the body's sodium is contained in bone. Approximately 2-5% occurs within organs and cells and the remaining 55% is in blood plasma and other extracellular fluids. Sodium must be maintained at a specific concentration in the blood and the fluid surrounding the body's cells for the body to function properly. The body maintains a balance of sodium in the blood by matching the amount of sodium we take in with the amount excreted (put out) by the kidneys. Hyponatremia occurs when the level of sodium in the blood becomes diluted by too much water intake.
The body continually regulates its handling of sodium. When dietary sodium is too high or low, the intestines and kidneys respond to adjust concentrations to normal. During the course of a day, the intestines absorb dietary sodium while the kidneys excrete a nearly equal amount of sodium into the urine. If a low sodium diet is consumed, the intestines increase their efficiency of sodium absorption, and the kidneys reduce its release into urine.
Causes & Development; Risk Factors
Hyponatremia can be caused by the following:- Kidney disorders in which the kidneys have difficulty eliminating fluids.
- Disorders in organs that control the body's regulation of sodium or water. The adrenal gland secretes a hormone called aldosterone that travels to the kidney, where it causes the kidney to retain sodium by not excreting it into the urine. Addison's disease causes hyponatremia as a result of low levels of aldosterone due to damage to the adrenal gland. The hypothalamus and pituitary gland are also involved in sodium regulation by making and releasing vasopressin, known as anti-diuretic hormone, into the bloodstream. Like aldosterone, vasopressin acts in the kidney, but it causes it to reduce the amount of water released into urine. With more vasopressin production, the body conserves water, resulting in a lower concentration of plasma sodium. Certain types of cancer cells produce vasopressin, leading to hyponatremia.
- Abnormal consumption or excretion of dietary sodium or water.
- Diuretic drugs used to treat high blood pressure. These drugs make the kidneys produce more urine, which can wash away too much sodium, especially when the patient is following a low sodium diet. This is especially of concern in elderly patients, who have a reduced ability to regulate the concentrations of various nutrients in the bloodstream. Diuretic drugs that frequently cause hyponatremia include furosemide (Lasix), bumetanide (Bumex), and most commonly, the thiazides. Diuretics enhance the excretion of sodium into the urine, with the goal of correcting high blood pressure. However, too much sodium excretion can result in hyponatremia. Usually only mild hyponatremia occurs in patients taking diuretics, but when combined with a low sodium diet or with the excessive drinking of water, severe hyponatremia can develop.
- Some psychiatric disorders cause people to drink extremely large quantities of water, which can result in hyonatremia.
- Drinking excess water sometimes causes hyponatremia, because the absorption of water into the bloodstream can dilute the sodium in the blood. This cause of hyponatremia is rare, but has been found in psychotic patients who compulsively drink more than 20 liters of water per day.
- Receiving too much fluid intravenously.
- Excessive drinking of beer, which is mainly water and low in sodium, can also produce hyponatremia when combined with a poor diet.
- Maintenance of a low salt diet for many months.
- Severe and prolonged diarrhea can also cause hyponatremia. Severe diarrhea, causing the daily output of 8-10 liters of fluid from the large intestines, results in the loss of large amounts of water, sodium, and various nutrients. Some diarrheal diseases release particularly large quantities of sodium and are therefore most likely to cause hyponatremia.
- Prolonged vomiting.
- Excessive sweat loss during a race on a hot day can present a challenge to the body to conserve adequate sodium levels. Marathon running, under certain conditions, leads to hyponatremia. Races of 25-50 miles can result in the loss of great quantities (8 to 10 liters) of sweat, which contains both sodium and water. Studies show that about 30% of marathon runners experience mild hyponatremia during a race. But runners who consume only pure water during a race can develop severe hyponatremia because the drinking water dilutes the sodium in the bloodstream. Such runners may experience neurological disorders as a result of the severe hyponatremia and require emergency treatment.
- Hypothalamus and pituitary disorders.
- Certain types of cancer.
Hyponatremia is more likely to occur in people whose kidneys do not function properly, as well as in those with heart failure, cirrhosis of the liver, and Addison's disease, in which underactive adrenal glands excrete too much sodium.
Signs & Symptoms
Because the brain is very sensitive to sodium levels, low sodium causes symptoms including confusion and lethargy. The patient may feel nauseated, and experience muscle twitching, which can progress to seizures. Eventually, severe hyponatremia can lead to coma and death.
Symptoms of moderate hyponatremia include tiredness, disorientation, headache, muscle cramps, and nausea. Severe hyponatremia can lead to seizures and coma. These neurological symptoms are thought to result from the movement of water into brain cells, causing them to swell and disrupt their functioning.
Diagnosis & Tests
In most cases of hyponatremia, doctors are primarily concerned with discovering the underlying disease causing the decline in plasma sodium levels.
Hyponatremia is diagnosed by acquiring a blood sample, preparing plasma, and using a sodium-sensitive electrode for measuring the concentration of sodium ions. Normal blood sodium levels are 136 to 145 milliequivalents per liter (mEq/L) of blood. A patient with hyponatremia will have a blood sodium level lower than 136 mEq/L.
Unless the cause is obvious, a variety of tests are subsequently run to determine if sodium was lost from the urine, diarrhea, or from vomiting. Tests are also used to determine abnormalities in aldosterone or vasopressin levels. The patient's diet and use of diuretics must also be considered.
Treatment & Prevention
Severe hyponatremia can be treated by infusing a solution of 5% sodium chloride in water into the bloodstream. Moderate hyponatremia due to use of diuretics or an abnormal increase in vasopressin is often treated by instructions to drink less water each day. Hyponatremia due to adrenal gland insufficiency is treated with hormone injections.
When hyponatremia is severe, it is considered a medical emergency that is treated in a hospital. Very low plasma sodium levels can result in seizures and coma. The doctor will slowly increase the blood sodium levels with intravenous (IV) fluids. Additional treatment depends upon the underlying cause of hyponatremia.
If you take diuretics, make sure you have your blood sodium levels checked on a regular basis. If you are sick and symptoms include vomiting or diarrhea, follow your doctor's recommendations for replacing lost fluids with clear liquids or electrolyte replacement fluids. People who run marathons and train intensely should drink electrolyte replacement fluids to keep sodium levels balanced.
Prognosis; Complications
Hyponatremia is just one manifestation of a variety of disorders. While hyponatremia can easily be corrected, the prognosis for the underlying condition that causes it varies.
Death that occurs during hyponatremia is usually due to other features of the disease rather than to the hyponatremia itself.
|
|
 |
|
 |
Recommendations and treatments for Hyponatremia (Low Blood Sodium Level): | | | | | Diet |  Reduced Water Consumption | Mild hyponatremia is treated by reducing water intake and monitoring the use of diuretics. |
|
Mineral |
Increased Salt Consumption| | The concentration of sodium in the blood plasma depends on the total amount of sodium and water in the circulatory system. Hyponatremia, can be corrected either by increasing sodium or by decreasing body water. |
|
| | | | |
KEY | | Highly recommended |
GLOSSARY
Addison's Disease
A condition characterized by the chronic destruction of the adrenal cortex, which leads to an increased loss of sodium and water in the urine, muscle weakness and low blood pressure. The bronze color of the skin is due to the increased production of the skin pigment, melanin.
Adrenal (Adrenal Gland, Adrenal Glands, Adrenals)
The adrenal glands sit on top of each kidney and consist of an outer cortex and an inner medulla. Of the 50 or so hormones the adrenals make, only cortisone and adrenaline are recognized by most people. Some of these hormones must be produced to preserve life, while others help resist stress. Other hormones from the adrenals control normal energy output (along with the thyroid) and govern the breakdown of stored energy into quick energy sources. The medulla produces epinephrine and norepinephrine, which are specifically designed to help the body deal with stressful situations. The adrenals control the body's potassium/sodium balance, which is vital for energy production. They also produce sex hormones in minute amounts, which is important for later years when the gonads drop or cease their production.
Aldosterone
A steroid hormone secreted by the adrenal cortex that helps the kidneys regulate the amount of salt and water in your body and, thus, regulate your blood pressure. When aldosterone levels drop too low, your kidneys cannot keep your salt and water levels in balance, and your blood volume and blood pressure drop.
Cancer
Refers to the various types of malignant neoplasms that contain cells growing out of control and invading adjacent tissues, which may metastasize to distant tissues.
Cirrhosis (Liver Cirrhosis)
A long-term disease in which the liver becomes covered with fiber-like tissue. This causes the liver tissue to break down and become filled with fat. All functions of the liver then decrease, including the production of glucose, processing drugs and alcohol, and vitamin absorption. Stomach and bowel function, and the making of hormones are also affected.
Cramp (Cramping, Cramps)
A sudden, involuntary, painful muscular contraction.
Diarrhea
Excessive discharge of contents of bowel.
Diuretic (Diuretics)
An agent increasing urine flow, causing the kidneys to excrete more than the usual amount of sodium, potassium and water.
Electrolyte (Electrolytes)
An element or compound that, when melted or dissolved in water or other solvent, breaks up into ions and is able to carry an electric current.
Gland (Glands)
The glandular system is one of the most important and complicated systems of the body. Gland tissue can be either an organ or general tissue that secretes chemicals and there are two types of gland: exocrine and endocrine. Those glands which secrete chemicals through tubules or ducts are called exocrine and include sweat, tear and salivary glands. Ductless glands - part of the endocrine system - secrete special chemicals (hormones) directly into the blood.
Hormones (Hormone)
Chemical substances secreted by a variety of body organs that are carried by the bloodstream and usually influence cells some distance from the source of production. Hormones signal certain enzymes to perform their functions and, in this way, regulate such body functions as blood sugar levels, insulin levels, the menstrual cycle, and growth. These can be prescription, over-the-counter, synthetic or natural agents. Examples include adrenal hormones such as corticosteroids and aldosterone; glucagon, growth hormone, insulin, testosterone, estrogens, progestins, progesterone, DHEA, melatonin, and thyroid hormones such as thyroxine and calcitonin.
Hypothalamus (Hypothalmus)
Tucked deep inside the brain, this gland is an important supervisory center, regulating many body functions. It is important for longevity and coordinates the entire endocrine system, especially in connection with the pituitary. The hypothalamus is located immediately below the thalamus at the center of the brain, and controls many automatic functions of the body. This means it has the power to govern the autonomic (automatic or subconscious) nervous system. The hypothalamus also controls pituitary output by secreting specific chemicals to the pituitary's front lobe. Despite its importance in maintaining homeostasis, the hypothalamus in humans accounts for only 1/300 of total brain weight, and is about the size of an almond.
Intravenous Infusion (IV)
A small needle placed in the vein to assist in fluid replacement or the giving of medication.
Kidneys (Kidney, Renal)
Bean-shaped organs, each about the size of a fist. They are located near the middle of the back, just below the rib cage. The kidneys are sophisticated reprocessing machines, each day handling about 50 gallons of blood to sift out about half a gallon of waste products and extra water. The waste and extra water become urine, which flows to the bladder through tubes called ureters. The actual filtering occurs in tiny units inside the kidneys called nephrons. Every kidney has about a million nephrons. In a nephron, a glomerulus -- which is a tiny blood vessel, or capillary -- intertwines with a tiny urine-collecting tube called a tubule. A complicated chemical exchange takes place, as waste materials and water leave your blood and enter your urinary system. The kidneys recycle chemicals such as sodium, phosphorus, and potassium and thus regulate their levels. Renal: Pertaining to the kidneys.
Liter (Liters, Litre, Litres)
A metric measure of volume equivalent to 1.057 liquid quarts or 0.2642 gallons.
Liver (Hepatic)
The largest and one of the most complex organs of the body, the liver is responsible for much of the metabolism of fats, proteins and carbohydrates. It is the site of much of the body's detoxification. It is connected very closely with digestion and the regulation of blood sugar, among many other functions. Found behind the ribs on the right side of the abdomen, it has many important functions such as removing harmful material from the blood, making enzymes and bile that help digest food, and converting food into substances needed for life and growth. Hepatic: Pertaining to the liver.
Nausea
Symptoms resulting from an inclination to vomit.
Pituitary (Pituitary Gland)
The pituitary gland is a small (half-inch), bean-shaped organ that hangs down from the lower center of the brain on a stalk attached to another gland, the hypothalamus. Weighing less than one gram, the pituitary gland is often called the "master gland" since it controls the secretion of hormones by other endocrine glands. It regulates many body activities, and is partitioned into front and back lobes. The front lobe is stimulated by the hypothalamus, and produces any one of six different hormones that in turn stimulate the thyroid, adrenal and reproductive glands, and also breast milk production.
Prognosis
A prediction (estimate) of the future course and outcome of a disease and an indication of the likelihood of recovery from that disease.
Seizure (Seizures)
While there are over 40 types of seizure, most are classed as either partial seizures which occur when the excessive electrical activity in the brain is limited to one area or generalized seizures which occur when the excessive electrical activity in the brain encompasses the entire organ. Although there is a wide range of signs, they mainly include such things as falling to the ground; muscle stiffening; jerking and twitching; loss of consciousness; an empty stare; rapid chewing/blinking/breathing. Usually lasting from between a couple of seconds and several minutes, recovery may be immediate or take up to several days.
Sodium
An essential mineral that our bodies regulate and conserve. Excess sodium retention increases the fluid volume (edema) and low sodium leads to less fluid and relative dehydration. The adult body averages a total content of over 100 grams of sodium, of which a surprising one-third is in bone. A small amount of sodium does get into cell interiors, but this represents only about ten percent of the body content. The remaining 57 percent or so of the body sodium content is in the fluid immediately surrounding the cells, where it is the major cation (positive ion). The role of sodium in the extracellular fluid is maintaining osmotic equilibrium (the proper difference in ions dissolved in the fluids inside and outside the cell) and extracellular fluid volume. Sodium is also involved in nerve impulse transmission, muscle tone and nutrient transport. All of these functions are interrelated with potassium.
Last updated: Apr 27, 2008
|
 |
|
|
