sodium
[so´de-um] a chemical element, atomic number 11, atomic weight 22.990, symbol Na. (See Appendix 6.) Sodium is the major cation of the extracellular fluid, constituting 90 to 95 per cent of all cations in the blood plasma and interstitial fluid; it thus determines the osmolality of the extracellular fluid. The serum sodium concentration is normally about 140 mEq/L. If the sodium level and osmolality fall,
osmoreceptors in the
hypothalamus are stimulated and cause the release of
antidiuretic hormone from the posterior lobe of the
pituitary gland. This hormone increases the absorption of water in the collecting ducts of the kidneys so that water is conserved while sodium and other electrolytes are excreted in the urine. If the sodium level and osmolality rise, neurons in the thirst center of the hypothalamus are stimulated. The thirsty person then drinks enough water to restore the osmolality of the extracellular fluid to the normal level.
A decrease in the serum sodium concentration (
hyponatremia) can occur in a variety of conditions. It is often associated with
deficient fluid volume due to diarrhea or vomiting when water is replaced faster than sodium. It can also occur in
syndrome of inappropriate antidiuretic hormone, in the late stages of
congestive heart failure or
cirrhosis of the liver, in acute or chronic
renal failure, and in
diuretic therapy. An increase in the serum sodium concentration (
hypernatremia) occurs when insensible water loss is not replaced by drinking, as in a comatose patient with diabetes insipidus.
sodium ascorbate an
antiscorbutic vitamin and nutritional supplement for parenteral administration. It is also used as an aid to
deferoxamine therapy in the treatment of chronic iron toxicity.
sodium benzoate an antifungal agent also used in a test of liver function.
sodium bicarbonate NaHCO
3, a white powder commonly found in households. It has a wide variety of uses in chemistry, in pharmaceuticals, and in consumer products. It is sometimes taken in water as a remedy for acid indigestion but should not be used regularly since when taken in excess it tends to cause
alkalosis. It can be mixed with water and applied as a paste for relief of pain in treatment of minor
burns and
insect bites and stings. A cupful in the bath water may help relieve itching caused by an allergic reaction. Called also
baking soda and
bicarbonate of soda.
sodium carbonate a compound now used primarily as an alkalizing agent in pharmaceuticals; it has been used as a lotion or bath in the treatment of scaly skin, and as a detergent.
sodium chloride common table
salt, a necessary constituent of the body and therefore of the diet, involved in maintaining osmotic tension of blood and tissues; uses include replenishment of electrolytes in the body, irrigation of wounds and body cavities, enema, inhaled mucolytic, topical osmotic ophthalmic agent, and preparation of pharmaceuticals. Called also
salt.
sodium citrate a sodium salt of citric acid, used as an
anticoagulant for blood or plasma that is to be fractionated or for blood that is to be stored. It is also administered orally as a urinary alkalizer.
dibasic sodium phosphate a salt of
phosphoric acid; used alone or in combination with other phosphate compounds, it is given intravenously as an
electrolyte replenisher, orally or rectally as a
laxative, and orally as a urinary acidifier and for prevention of
kidney stones.
sodium fluoride a
dental caries preventative used in
fluoridation of drinking water or applied topically to teeth. Topical preparations include gels (sodium fluoride and phosphoric acid gel, also called APF gel) and solutions (sodium fluoride and acidulated phosphate topical solution, also called APF solution).
sodium hydroxide NaOH, a strongly alkaline and caustic compound; used as an alkalizing agent in pharmaceuticals.
sodium hypochlorite a compound having germicidal, deodorizing, and bleaching properties; used in solution to disinfect utensils, and in diluted form (
Dakin's solution) as a local antibacterial.
sodium iodide a compound used as a source of
iodine.
sodium lactate a compound used in solution to replenish body fluids and electrolytes.
monobasic sodium phosphate 2. a monosodium salt of
phosphoric acid; used in buffer solutions. Used alone or in combination with other phosphate compounds, it is given intravenously as an
electrolyte replenisher, orally or rectally as a
laxative, and orally as a urinary acidifier and for prevention of
kidney stones.
sodium monofluorophosphate a
dental caries preventative applied topically to the teeth.
sodium nitrite an antidote for
cyanide poisoning; also used as a preservative in cured meats and other foods.
sodium nitroprusside an
antihypertensive agent used in the treatment of acute congestive heart failure and of hypertensive crisis and to produce controlled hypotension during surgery; also used as a reagent.
sodium phenylbutyrate an agent used as adjunctive treatment to control the
hyperammonemia of pediatric urea cycle enzyme disorders.
sodium propionate a salt used as an
antifungal preservative in foods and pharmaceuticals and as a topical antifungal
agent.
Miller-Keane Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health, Seventh Edition. © 2003 by Saunders, an imprint of Elsevier, Inc. All rights reserved.