Sep. 09, 2024
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Barium sulfate is ingested by mouth or administered rectally and combined with granules of effervescent bicarbonate to enhance distension of the GI tract, allowing for enhanced gastrointestinal tract visualization 3 , 5 .
This drug is used as a contrast agent in diagnostic x-ray procedures. Therapeutic advantages of barium sulfate in diagnostic procedures include both its low water solubility and high level of clearance from the body Label .
Barium sulfate occurs in nature as the mineral barite. It is also used in various manufacturing applications and mixed into heavy concrete to serve as a radiation shield 3 .
Barium sulfate is a contrast agent used for CT scans of the gastrointestinal tract.
Barium sulfate increases the absorption of x-rays as they are passed throughout the body, delineating body structures, in which barium sulfate is localized. This allows for the clear visualization of normal organs/defect in normal anatomy 5.
Barium sulfate is a heavy metal with a high atomic number (Z=56) and a K shell binding energy (K-edge of 37.4 keV) very close to that of most diagnostic x-ray beams. Due to these characteristics, barium is an ideal medium for the absorption of x-rays Label.
Barium sulfate is essentially not absorbed from the GI tract nor metabolized in the body. Barium sulfate is used to fill the gastrointestinal tract lumen or to coat the mucosal surface and is administered orally, rectally, or instilled into an enterostomy tube or catheter Label, 5.
Barium sulfate enhances delineation of the GI tract. The barium suspension covers the mucosal surface of the GI tract, allowing its shape, distensibility, motion, integrity, continuity, location within the torso, relationship to other organs to be closely examined 5. Various abnormalities, such as benign or malignant tumors, ulcers, strictures, diverticula, inflammation or infection, altered motility, displacement and other pathology can thereby be identified Label, 5.
At lower concentrations (higher dilution), barium enhances the conspicuity of the GI tract to differentiate the GI tract from various abdominal organs in computed tomography examinations (CT scans) of the abdomen. Improved delineation of the gastrointestinal tract lumen and mucosa may be reached by contrast provided by gas (by the addition of bicarbonate or gas-filled balloons) in addition to the barium 5. This is known as a double-contrast procedure. Osmotically active agents (for example, sorbitol) are also used to induce fluid accumulation and distension of the GI system to enhance visualization 5.
Barium sulfate is not absorbed following oral or rectal administration with a normal gastrointestinal tract. In patients with a normal GI tract, barium sulfate is normally excreted within 24 hr after oral ingestion. Post rectal administration of barium sulfate suspensions, the drug is generally excreted when the enema is released. Some barium may remain in the colon for several weeks, however, and eventually clears, especially in patients with impaired intestinal peristalsis 3. It is difficult to quantify the uptake of ingested barium because of a number of factors affect its absorption. The presence of sulfate in food can cause the precipitation of barium sulfate 3.
The following is the approximate time to peak opacification of organs by barium sulfate in a healthy GI tract:
Esophagus, stomach, and duodenum uptake of barium sulfate occurs almost immediately after oral administration 4.
Small intestine uptake is dependent on gastric emptying rate and viscosity of the preparation; it may be delayed 15-90 minutes post ingestion 4.
Small intestine (enteroclysis studies) uptake is immediate, following direct instillation 4.
Colon and distal small intestine uptake are dependent on patient positioning. Hydrostatic pressure also determines the rate and degree of opacification 4.
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Barium sulfate is poorly water soluble and shows negligible levels of absorption from the gastrointestinal tract following both oral or rectal administration. In healthy subjects, orally administered barium sulfate is generally excreted within 24 hours. Rectally administered barium sulfate is eliminated with clearance of the enema 5.
Barium sulfate is excreted unchanged in the feces 3.
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The rate of excretion of barium sulfate is dependent on the route of administration and the status of peristaltic activity and motility of the gastrointestinal tract 5.
Acute Exposure
Nausea, vomiting, diarrhea and abdominal cramping may occur Label. Acute exposure to barium sulfate may irritate the eyes and respiratory tract. Exposure to inhalation or other forms can affect the nervous system and lead to hypokalemia, which can contribute to cardiovascular rhythm abnormality 3. Hypersensitivity, gastrointestinal transit delay, obstruction, aspiration pneumonitis and systemic embolization of barium sulfate are more serious complications of administration Label. In addition, fatalities have occurred due to aspiration pneumonitis, barium sulfate impaction, intestinal perforation with subsequent peritonitis and granuloma formation, and vasovagal and syncopal episodes Label, 2.
*Chronic Exposure *
The lungs may be affected by repeated or prolonged exposure to dust particles, resulting in baritosis (a type of benign pneumoconiosis) 3. Inhalation of barium sulfate dust may lead to a benign pneumoconiosis ("baritosis") with conspicuous radiographic characteristics but no signs of impairment of pulmonary function 3.
Intra-abdominal leakage
Intra-abdominal leakage may occur during or after administration of barium sulfate Label,5. Caution is advised in patients with a history of food aspiration and in patients with diagnosed swallowing disorders Label.
** A note on GI perforation**
Perforation of the colon after rectal administration of barium sulfate suspension has been reported due to the increased hydrostatic pressure of the instilled suspension, trauma to the colon from an enema tip, or forceful or deep insertion of a non-flexible enema tip. Perforation of the bowel has been followed by peritonitis, adhesions, granulomas, and death 4. This is a rare occurrence. Injury to the rectal mucosa or anal canal due to the enema tip or retention balloon is likely the most common traumatic cause of perforation during treatment. Inflation of a balloon within a stricture, neoplasm, inflamed rectum, or stoma is hazardous, and caution should be exerted 1.
Carcinogenicity and mutagenicity
No animal studies have been performed to evaluate the carcinogenicity of barium sulfate or potential effects on reproduction Label. Elective contrast radiography of the abdomen is not routintely recommended during pregnancy because of the risks to the fetus from radiation exposure 4.
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Barium sulfate (or sulphate) is the inorganic compound with the chemical formula BaSO4. It is a white crystalline solid that is odorless and insoluble in water. It occurs in nature as the mineral barite, which is the main commercial source of barium and materials prepared from it. Its opaque white appearance and its high density are exploited in its main applications.[4]
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About 80% of the world's barium sulfate production, mostly purified mineral, is consumed as a component of oil well drilling fluid. It increases the density of the fluid,[5] increasing the hydrostatic pressure in the well and reducing the chance of a blowout.
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Barium sulfate in suspension is often used medically as a radiocontrast agent for X-ray imaging and other diagnostic procedures. It is most often used in imaging of the GI tract during what is colloquially known as a "barium meal". It is administered orally, or by enema, as a suspension of fine particles in a thick milk-like solution (often with sweetening and flavoring agents added). Although barium is a heavy metal, and its water-soluble compounds are often highly toxic, the low solubility of barium sulfate protects the patient from absorbing harmful amounts of the metal. Barium sulfate is also readily removed from the body, unlike Thorotrast, which it replaced. Due to the relatively high atomic number (Z = 56) of barium, its compounds absorb X-rays more strongly than compounds derived from lighter nuclei.
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The majority of synthetic barium sulfate is used as a component of white pigment for paints. In oil paint, barium sulfate is almost transparent[citation needed], and is used as a filler or to modify consistency. One major manufacturer of artists' oil paint sells "permanent white" that contains a mixture of titanium white pigment (TiO2) and barium sulfate. The combination of barium sulfate and zinc sulfide (ZnS) is the inorganic pigment called lithopone. In photography it is used as a coating for certain photographic papers.[5] It is also used as a coating to diffuse light evenly.
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Barium sulfate is highly reflective, of both visible and ultraviolet light.[6] Researchers used it as an ingredient in paint that reflects 98.1% of solar radiation, allowing surfaces to which it has been applied to stay cooler in sunlit conditions. Commercially available white paints only reflect 80 - 90% of solar radiation.[7] By using hexagonal nanoplatelet boron nitride, the thickness of a coat of this type of paint was reduced to 0.15 mm.[6]
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A thin layer of barium sulfate called baryta is first coated on the base surface of most photographic paper to increase the reflectiveness of the image, with the first such paper introduced in in Germany.[8] The light-sensitive silver halide emulsion is then coated over the baryta layer. The baryta coating limits the penetration of the emulsion into the fibers of the paper and makes the emulsion more even, resulting in more uniform blacks.[9] Further coatings may then be present for fixing and protection of the image. Baryta has also been used to brighten papers intended for ink-jet printing.[10]
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Barium sulfate is commonly used as a filler for plastics to increase the density of the polymer in vibrational mass damping applications. In polypropylene and polystyrene plastics, it is used as a filler in proportions up to 70%. It has an effect of increasing acid and alkali resistance and opacity. Such composites are also used as X-ray shielding materials due to their enhanced radio-opacity.[11] In cases where machinability and weight are a concern, composites with high mass fraction (70&#;80%) of barium sulfate may be preferred to the more commonly used steel shields.[12]
Barium sulfate can also be used to enhance the material properties of HDPE,[13] although typically in relatively low concentrations, and often in combination with other fillers like calcium carbonate or titanium oxide.
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Barium sulfate is used in soil testing. Tests for soil pH and other qualities of soil use colored indicators, and small particles (usually clay) from the soil can cloud the test mixture and make it hard to see the color of the indicator. Barium sulfate added to the mixture binds with these particles, making them heavier so they fall to the bottom, leaving a clearer solution.
In colorimetry, barium sulfate is used as a near-perfect diffuser when measuring light sources.
In metal casting, the moulds used are often coated with barium sulfate in order to prevent the molten metal from bonding with the mould.
It is also used in brake linings, anacoustic foams, powder coatings, and root canal filling.
Barium sulfate is an ingredient in the "rubber" pellets used by Chilean police.[14] This together with silica helps the pellet attain a 96.5 Shore A hardness.[14]
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Barium sulfate is used as a catalyst support when selectively hydrogenating functional groups that are sensitive to overreduction. With a low surface area, the contact time of the substrate with the catalyst is shorter and thus selectivity is achieved. Palladium on barium sulfate is also used as a catalyst in the Rosenmund reduction.
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As barium compounds emit a characteristic green light when heated at high temperature, barium salts are often used in green pyrotechnic formulas, although nitrate and chlorate salts are more common. Barium sulfate is commonly used as a component of "strobe" pyrotechnic compositions.
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As barium sulfate has a high melting point and is insoluble in water, it is used as a release material in casting of copper anode plates. The anode plates are cast in copper molds, so to avoid the direct contact of the liquid copper with the solid copper mold, a suspension of fine barium sulfate powder in water is used as a coating on the mold surface. Thus, when the molten copper solidifies in form of an anode plate it can be easily released from its mold.
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Barium sulfate is sometimes used, besides polytetrafluoroethylene (PTFE), to coat the interior of integrating spheres due to the high reflectance of the material and near Lambertian characteristics.
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Barium sulfate is listed among the materials acceptable to the Bureau of Alcohol, Tobacco, Firearms and Explosives (BATFE) for the manufacturing of firearms and/or components that are made of plastic, to achieve compliance with the U.S. federal requirement that an X-ray machine must be able to accurately depict the shape of the plastic firearm or component.[15]
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Almost all of the barium consumed commercially is obtained from barite, which is often highly impure. Barite is processed by thermo-chemical sulfate reduction (TSR), also known as carbothermal reduction (heating with coke) to give barium sulfide:
In contrast to barium sulfate, barium sulfide is soluble in water and readily converted to the oxide, carbonate, and halides. To produce highly pure barium sulfate, the sulfide or chloride is treated with sulfuric acid or sulfate salts:
Barium sulfate produced in this way is often called blanc fixe, which is French for "permanent white". Blanc fixe is the form of barium encountered in consumer products, such as paints.[5]
In the laboratory barium sulfate is generated by combining solutions of barium ions and sulfate salts. Because barium sulfate is the least toxic salt of barium due to its insolubility, wastes containing barium salts are sometimes treated with sodium sulfate to immobilize (detoxify) the barium. Barium sulfate is one of the most insoluble salts of sulfate. Its low solubility is exploited in qualitative inorganic analysis as a test for Ba2+ ions, as well as for sulfate.
Untreated raw materials such as natural baryte formed under hydrothermal conditions may contain many impurities, a.o., quartz, or even amorphous silica.[16]
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Barium sulfate is reduced to barium sulfide by carbon. The accidental discovery of this conversion many centuries ago led to the discovery of the first synthetic phosphor.[4] The sulfide, unlike the sulfate, is water-soluble.
During the early part of the 20th century, during the Japanese colonization period, hokutolite was found to exist naturally in the Beitou hot-springs area near Taipei City, Taiwan. Hokutolite is a radioactive mineral composed mostly of PbSO4 and BaSO4, but also containing traces of uranium, thorium and radium. The Japanese harvested these elements for industrial uses, and also developed dozens of &#;therapeutic hot-spring baths&#; in the area.[17]
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Although soluble salts of barium are moderately toxic to humans, barium sulfate is nontoxic due to its insolubility. The most common means of inadvertent barium poisoning arises from the consumption of soluble barium salts mislabeled as BaSO4. In the Celobar incident (Brazil, ), nine patients died from improperly prepared radiocontrast agent. In regards to occupational exposures, the Occupational Safety and Health Administration set a permissible exposure limit at 15 mg/m3, while the National Institute for Occupational Safety and Health has a recommended exposure limit at 10 mg/m3. For respiratory exposures, both agencies have set an occupational exposure limit at 5 mg/m3.[18]
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