Saline (medicine) - AbsoluteAstronomy.com

Medicine

Medicine is the science and art of healing. It encompasses a variety of health care practices evolved to maintain and restore health by the prevention and treatment of illness....

, saline (also saline solution) is a general term referring to a sterile solution of sodium chloride

Sodium chloride

Sodium chloride, also known as salt, common salt, table salt or halite, is an inorganic compound with the formula NaCl. Sodium chloride is the salt most responsible for the salinity of the ocean and of the extracellular fluid of many multicellular organisms...

(NaCl, more commonly known as salt

Salt

In chemistry, salts are ionic compounds that result from the neutralization reaction of an acid and a base. They are composed of cations and anions so that the product is electrically neutral...

) in water but is only sterile when it is to be placed intravenously, otherwise, a saline solution is a salt water

Salt water

Salt water or saltwater may refer to:* Saline water, water containing salts* Brine, with salt* Brackish water, water that is saltier than fresh water, but not as salty as seawater* Seawater, water from oceans or seas...

solution. The sterile solution is typically used for intravenous infusion, rinsing contact lens

Contact lens

A contact lens, or simply contact, is a lens placed on the eye. They are considered medical devices and can be worn to correct vision, for cosmetic or therapeutic reasons. In 2004, it was estimated that 125 million people use contact lenses worldwide, including 28 to 38 million in the United...

es, nasal irrigation

Nasal irrigation

Nasal irrigation or nasal lavage or nose douche is the personal hygiene practice in which the nasal cavity is washed to flush out excess mucus and debris from the nose and sinuses. The practice is well-tolerated and beneficial with only minor side effects...

, and often used to clean a new piercing. Saline solutions are available in various formulations for different purposes. Salines are also used in cell biology, molecular biology, and biochemistry experiments.

Concentrations

Concentrations vary from low to normal to high. High concentrations are used rarely in medicine

Medicine

Medicine is the science and art of healing. It encompasses a variety of health care practices evolved to maintain and restore health by the prevention and treatment of illness....

but frequently in molecular biology

Molecular biology

Molecular biology is the branch of biology that deals with the molecular basis of biological activity. This field overlaps with other areas of biology and chemistry, particularly genetics and biochemistry...

Normal

Normal saline (NS) — is the commonly-used term for a solution of 0.90% w/v of NaCl

Sodium chloride

, about 300 mOsm/L or 9.0 g per liter. Less commonly, this solution is referred to as physiological saline or isotonic saline, neither of which is technically accurate. NS is used frequently in intravenous drips (IVs) for patients who cannot take fluids orally and have developed or are in danger of developing dehydration

Dehydration

In physiology and medicine, dehydration is defined as the excessive loss of body fluid. It is literally the removal of water from an object; however, in physiological terms, it entails a deficiency of fluid within an organism...

or hypovolemia

Hypovolemia

In physiology and medicine, hypovolemia is a state of decreased blood volume; more specifically, decrease in volume of blood plasma...

. NS is typically the first fluid used when hypovolemia is severe enough to threaten the adequacy of blood circulation, and has long been believed to be the safest fluid to give quickly in large volumes. However, it is now known that rapid infusion of NS can cause metabolic acidosis

Metabolic acidosis

In medicine, metabolic acidosis is a condition that occurs when the body produces too much acid or when the kidneys are not removing enough acid from the body. If unchecked, metabolic acidosis leads to acidemia, i.e., blood pH is low due to increased production of hydrogen by the body or the...

.

The solution is 9 grams of sodiumchloride (NaCl) dissolved in water, to a total volume of 1000 ml. The mass of 1 millilitre of normal saline is 1.0046 grams at 22°C. The molecular weight of sodium chloride is approximately 58.5 grams per mole, so 58.5 grams of sodium chloride equals 1 mole. Since normal saline contains 9 grams of NaCl, the concentration is 9 grams per liter divided by 58.5 grams per mole, or 0.154 moles per liter.
Since NaCl dissociates into two ions – sodium and chloride – 1 molar NaCl is 2 osmolar.
Thus, NS contains 154 mEq

Equivalent (chemistry)

The equivalent , sometimes termed the molar equivalent, is a unit of amount of substance used in chemistry and the biological sciences.The equivalent is formally defined as the amount of a substance which will either:...

/L of Na⁺ and Cl⁻. It has a slightly higher degree of osmolarity (i.e. more solute

Solution

In chemistry, a solution is a homogeneous mixture composed of only one phase. In such a mixture, a solute is dissolved in another substance, known as a solvent. The solvent does the dissolving.- Types of solutions :...

per litre) than blood

Blood

Blood is a specialized bodily fluid in animals that delivers necessary substances such as nutrients and oxygen to the cells and transports metabolic waste products away from those same cells....

(However, if you take into account the osmotic coefficient

Osmotic coefficient

An osmotic coefficient φ is a quantity which characterises the deviation of a solvent from ideal behaviour, referenced to Raoult's law. The osmotic coefficient on a molality basis is defined by:and on an amount fraction basis by:...

, a correction for non-ideal solutions, then the saline solution is much closer to isotonic. Osmotic coefficient of NaCl is about 0.93; therefore 0.154 x 1000 x 2 x .93 = 290). Nonetheless, the osmolarity of normal saline is a close approximation to the osmolarity of NaCl in blood.

Usage

For medical uses, saline is often used to flush wounds and skin abrasions. Normal Saline will not burn or sting when applied.

Saline is also used in I.V. therapy, intravenously supplying extra water to a dehydrated patient or supplying the daily water and salt needs ("maintenance" needs) of a patient who is unable to take them by mouth. Because infusing a solution of low osmolality can cause problems, intravenous solutions with reduced saline concentrations typically have dextrose (glucose

Glucose

Glucose is a simple sugar and an important carbohydrate in biology. Cells use it as the primary source of energy and a metabolic intermediate...

) added to maintain a safe osmolality while providing less sodium chloride. As the molecular weight (MW) of dextrose is greater, this has the same osmolality as normal saline despite having less sodium

Sodium

Sodium is a chemical element with the symbol Na and atomic number 11. It is a soft, silvery-white, highly reactive metal and is a member of the alkali metals; its only stable isotope is 23Na. It is an abundant element that exists in numerous minerals, most commonly as sodium chloride...

. Saline can also be used by addicts trying to rid their bodies of opiates and other illegal drugs, yet if not taken in the proper dose can have the opposite effect on an addicts body . Because the dextrose used in these preparations is dextrose monohydrate (a commercial form having MW 198 in contrast to MW 180 for glucose), 5% dextrose is equivalent to 4.5% glucose.

The amount of normal saline infused depends largely on the needs of the patient (e.g. ongoing diarrhea

Diarrhea

Diarrhea , also spelled diarrhoea, is the condition of having three or more loose or liquid bowel movements per day. It is a common cause of death in developing countries and the second most common cause of infant deaths worldwide. The loss of fluids through diarrhea can cause dehydration and...

or heart failure) but is typically between 1.5 and 3 litre

Litre

pic|200px|right|thumb|One litre is equivalent to this cubeEach side is 10 cm1 litre water = 1 kilogram water The litre is a metric system unit of volume equal to 1 cubic decimetre , to 1,000 cubic centimetres , and to 1/1,000 cubic metre...

s a day for an adult.

Rinse eye drops are often distributed for free by needle-exchange programmes. Containing normal saline, they are small, sterile, and safe for intravenous use.

Saline is also often used for nasal washes to relieve some of the symptoms of the common cold. This need not be sterile, as the nose cavity is not sterile either. In this case "home-made" saline may be used: this is made by dissolving approximately half a teaspoonful of table salt into a glass of clean tap water

Tap water

Tap water is a principal component of "indoor plumbing", which became available in urban areas of the developed world during the last quarter of the 19th century, and common during the mid-20th century...

Hypertonic saline

Hypertonic saline (NS) — 7% NaCl solutions are considered mucoactive agents and as such are used to hydrate thick secretions (mucous

Mucus

In vertebrates, mucus is a slippery secretion produced by, and covering, mucous membranes. Mucous fluid is typically produced from mucous cells found in mucous glands. Mucous cells secrete products that are rich in glycoproteins and water. Mucous fluid may also originate from mixed glands, which...

) in order to make it easier to cough up and out (expectorate). 3% hypertonic saline solutions are also used in critical care settings to help in haemorrhagic shock (but no other type of shock), acutely increased intracranial pressure

Intracranial pressure

Intracranial pressure is the pressure inside the skull and thus in the brain tissue and cerebrospinal fluid . The body has various mechanisms by which it keeps the ICP stable, with CSF pressures varying by about 1 mmHg in normal adults through shifts in production and absorption of CSF...

, or severe hyponatremia. Inhalation of hypertonic saline has also been shown to help in other respiratory problems, specifically bronchiolitis

Bronchiolitis

Bronchiolitis is inflammation of the bronchioles, the smallest air passages of the lungs. It usually occurs in children less than two years of age and presents with coughing, wheezing, and shortness of breath. This inflammation is usually caused by viruses...

. Hypertonic saline is currently recommended by the Cystic Fibrosis Foundation

Cystic Fibrosis Foundation

The Cystic Fibrosis Foundation is a non-profit organization in the United States established to provide the means to cure and control cystic fibrosis . The Foundation provides information about cystic fibrosis and finances CF research that aims to improve the quality of life for people with the...

as a primary part of a Cystic Fibrosis

Cystic fibrosis

Cystic fibrosis is a recessive genetic disease affecting most critically the lungs, and also the pancreas, liver, and intestine...

treatment regimen.

Mechanism of action

Aerosol — Nebulized hypertonic saline treatments disrupt the interaction between glycosaminoglycan

Glycosaminoglycan

Glycosaminoglycans or mucopolysaccharides are long unbranched polysaccharides consisting of a repeating disaccharide unit. The repeating unit consists of a hexose or a hexuronic acid, linked to a hexosamine .-Production:Protein cores made in the rough endoplasmic reticulum are posttranslationally...

s and IL-8, rendering IL-8 susceptible to proteolytic degradation with subsequent decrease in neutrophil chemotaxis; all of this ultimately reducing inflammation

Inflammation

Inflammation is part of the complex biological response of vascular tissues to harmful stimuli, such as pathogens, damaged cells, or irritants. Inflammation is a protective attempt by the organism to remove the injurious stimuli and to initiate the healing process...

Other

Other concentrations commonly used include:

Half-normal saline (0.45% NaCl), often with "D5" (5% dextrose), contains 77 mEq/L of Na and Cl and 50 g/L glucose.
Quarter-normal saline (0.22% NaCl) has 39 mEq/L of Na and Cl and always contains 5% dextrose for osmolality reasons.
Hypertonic saline may be used in perioperative fluid management protocols to reduce excessive intravenous fluid infusions and lessen pulmonary complications. Hypertonic saline is used in treating hyponatremia
Hyponatremia
Hyponatremia is an electrolyte disturbance in which the sodium concentration in the serum is lower than normal. In the vast majority of cases, hyponatremia occurs as a result of excess body water diluting the serum sodium and is not due to sodium deficiency. Sodium is the dominant extracellular...

and cerebral edema
Cerebral edema
Cerebral edema or cerebral œdema is an excess accumulation of water in the intracellular or extracellular spaces of the brain.-Vasogenic:Due to a breakdown of tight endothelial junctions which make up the blood-brain barrier...

Rapid correction of hyponatremia via hypertonic saline, or via any saline infusion > 40 mmol/L (Na+ having a valence of 1, 40 mmol/L = 40 mEq/L) greatly increases risk of central pontine myelinolysis
Central pontine myelinolysis
Central pontine myelinolysis is neurological disease caused by severe damage of the myelin sheath of nerve cells in the brainstem, more precisely in the area termed the pons, predominately of iatrogenic etiology...

(CPM), and so requires constant monitoring of patient response. Water privation combined with diuretic block does not produce as much risk of CPM as saline administration does; however, it does not correct hyponatremia as rapidly as administration of hypertonic saline does. Due to hypertonicity, administration may result in phlebitis
Phlebitis
Phlebitis is an inflammation of a vein, usually in the legs.When phlebitis is associated with the formation of blood clots , usually in the deep veins of the legs, the condition is called thrombophlebitis...

and tissue necrosis
Necrosis
Necrosis is the premature death of cells in living tissue. Necrosis is caused by factors external to the cell or tissue, such as infection, toxins, or trauma. This is in contrast to apoptosis, which is a naturally occurring cause of cellular death...

. As such, concentrations greater than 3% NaCl should normally be administered via a central venous catheter
Central venous catheter
In medicine, a central venous catheter is a catheter placed into a large vein in the neck , chest or groin...

, also known as a 'central line'. Such hypertonic saline is normally available in two strengths, the former of which is more commonly administered:
- 3% NaCl has 513 mEq/L of Na and Cl.
- 5% NaCl has 856 mEq/L of Na and Cl.
NaCl solutions that are less commonly used are 7% (1200 mEq/L) and 23.4% (approx 4000 mEq/L), both of which are used (also via central line), often in conjunction with supplementary diuretics, in the treatment of traumatic brain injury
Traumatic brain injury
Traumatic brain injury , also known as intracranial injury, occurs when an external force traumatically injures the brain. TBI can be classified based on severity, mechanism , or other features...

.
Dextrose (glucose) 4% in 0.18% saline is used sometimes for maintenance replacement.

Solutions of saline with added ingredients

In medicine, common types of salines include:

Lactated Ringer's solution
Lactated Ringer's solution
Lactated Ringer's solution is a solution that is isotonic with blood and intended for intravenous administration. It may also be given subcutaneously....
Acetated Ringer's solution

And in cell biology, in addition to the above the following are used:

Phosphate buffered saline
Phosphate buffered saline
Phosphate buffered saline is a buffer solution commonly used in biological research. It is a water-based salt solution containing sodium chloride, sodium phosphate, and, in some formulations, potassium chloride and potassium phosphate. The buffer's phosphate groups help to maintain a constant pH...

(PBS) (recipes from Dulbecco = D-PBS, Galfre, Kuchler, Ausubel etc.)
TRIS-buffered saline
Tris-Buffered Saline
Tris-buffered saline is a buffer used in some biochemical techniques to maintain the pH within a relatively narrow range. Tris has a slightly alkaline buffering capacity in the 7–9.2 range....

(TBS) (recipes from Goldsmith, Ausubel etc.)
Hank's balanced salt solution (HBSS)
Earle's balanced salt solution (EBSS)
Standard saline citrate (SSC)
HEPES
HEPES
HEPES is a zwitterionic organic chemical buffering agent; one of the twelve Good's buffers...

-buffered saline (HBS) (recipes from Dittmar, Liu, Ausubel etc.)
Gey's balanced salt solution (GBSS)

History

Saline was believed to have originated during the Indian Blue Cholera

Cholera

Cholera is an infection of the small intestine that is caused by the bacterium Vibrio cholerae. The main symptoms are profuse watery diarrhea and vomiting. Transmission occurs primarily by drinking or eating water or food that has been contaminated by the diarrhea of an infected person or the feces...

pandemic that swept across Europe in 1831. William Brooke O'Shaughnessy

William Brooke O'Shaughnessy

William Brooke O'Shaughnessy MD FRS was an Irish physician famous for his work in pharmacology and inventions related to telegraphy...

, a recent graduate of Edinburgh Medical School, proposed in an article to medical journal The Lancet

The Lancet

The Lancet is a weekly peer-reviewed general medical journal. It is one of the world's best known, oldest, and most respected general medical journals...

to inject cholera patients with highly-oxygenated salts to treat the "universal stagnation of the venous system and rapid cessation of arterialisation of the blood" seen in severely dehydrated cholera patients. He found his treatment harmless in dogs, and his proposal was soon adopted by the physician Thomas Latta in treating cholera patients to beneficial effect. In the following decades, variations and alternatives to Latta's solution were tested and used in treating cholera patients. These solutions contained a range of concentrations of sodium, chloride, potassium, carbonate, phosphate, and hydroxide. The breakthrough in achieving physiological concentrations was accomplished by Ringer in 1831, when he determined the optimal salt concentrations to maintain the contractility of frog heart muscle tissue. Normal saline is considered a descendant of the pre-Ringer solutions, as Ringer's findings were not adopted and widely used until decades later. The term "normal saline" itself appears to have little historical basis, except for Hartog Jakob Hamburger's 1882–83 in vitro studies of red cell lysis that incorrectly suggested that 0.9% was the concentration of salt in human blood (rather than 0.6%, the true concentration).