Tiêu đề 15. CAUSTICS - INORGANIC ACIDS AND ALKALI.pdf ✅

PHARMD GURU Page 1 INORGANIC ACIDS  Worldwide, 80% of caustic ingestions occur in young children; these are usually accidental ingestions of small amounts and are often benign.  In adults, caustic ingestions are frequently intentional ingestions of large amounts by suicidal people and are life-threatening.  Common sources of caustics include solid and liquid drain and toilet bowl cleaners.  Industrial products are usually more concentrated than household products and thus tend to be more damaging. CLASSIFICATION: All caustics are highly injurious locally and produce burns of varying severity and intensity. Three phases have been recognized. 1. Acute inflammatory phase (upto 7 days): Characterised by vascular thrombosis and cellular necrosis. The necrotic mucosa sloughs by the 3rd or 4th day, and an ulcer forms. 2. Latent granulation phase (1 to 2 weeks): The sloughed area of mucosa shows evidence of fibroplasia, and fresh granulation tissue is formed. Collagen starts to replace the granulation tissue by the end of the 1st week. Perforation is most common during this phase. 3. Chronic cicatrisation phase (after 2 weeks): There is formation of excessive scar tissue around the submucosa and muscularis mucosa resulting in contractures. ACIDS: Acids are chemicals capable of causing corrosive injury to tissues constitute a very large group of poisons. Most cause injury by acid-base reactions but damage can also result from hydrocarbon dissolution, re-dox reactions, denaturation, and alkylation reactions. Ingestion of acid causes more damage to the stomach than the oesophagus because the squamous CAUSTICS: INORGANIC ACIDS AND ALKALI
PHARMD GURU Page 2 epithelium of the latter is more resistant to acids, while it is just the opposite in the case of alkali ingestion where the columnar epithelium of the stomach is more resistant. INORGANIC ACIDS: Let’s look at the inorganic acids toxicology taking Sulfuric acid and Hydrofluoric acid as an example. Most inorganic acids have similar characteristics. SULFURIC ACID: Sulfuric acid is a heavy, oily, colourless, odourless, non-fuming liquid. It is hygroscopic, i.e. it has great affinity for water with which it reacts violently, giving off intense heat. Sulfuric acid is mainly used in two forms:  Commercial concentrated sulfuric acid is usually a 93-98% solution in water.  Fuming sulfuric acid is a solution of sulfur trioxide in sulfuric acid. USES: Sulfuric acid is probably the most widely used industrial chemical in most parts of the world.  It is used as a feedstock in the manufacture of a number of chemicals, e.g. acetic acid, hydrochloric acid, phosphoric acid, ammonium sulfate, barium sulfate, copper sulfate, phenol, synthetic fertilizers, dyes, pharmaceuticals, detergents, paint, etc.  Storage batteries utilize sulfuric acid as an electrolyte.  Sulfuric acid is also used in the leather, fur, food processing, wool, and uranium industries, for gas drying, and as a laboratory reagent.  Sulfuric acid can be formed in smog from the photochemical oxidation of sulfur dioxide to sulfur trioxide and subsequent reaction with water. It is a major component of acid rain.
PHARMD GURU Page 3 TOXICITY LEVEL: About 20 to 30 ml of concentrate sulfuric acid. Deaths have been reported with ingestion of as little as 3.5 ml. MECHANISM: Produces coagulation necrosis of tissues on contact. Systemic toxicity following corrosive injury is usually secondary to inflammation, acidosis, infection, and necrosis. CLINICAL (TOXIC) SYMPTOMS:  Organs particularly at risk from corrosive injury include the gastrointestinal tract, the eyes and lungs.  Burning pain from the mouth to the stomach. Abdominal pain is often severe.  Intense thirst. However, attempts at drinking water usually provoke retching.  The vomitus is brownish or blackish in color due to altered blood (coffee grounds vomit), and may contain shreds of the charred wall of the stomach.  Renal failure and decreased urine output can occur after several hours of uncorrected circulatory collapse.  Contact with the eyes can cause severe injury including conjunctivitis, periorbital oedema, corneal oedema and ulceration, necrotising keratitis, and iridocyclitis. INVESTIGATIONS/DIAGNOSIS:  Litmus test: The pH of the saliva can be tested with a litmus paper to determine whether the chemical ingested is an acid or an alkali (turns red in acid, and blue in alkaline solution).  Fresh stains in clothing may be tested by adding a few drops of sodium carbonate. Production of effervescence (bubbles) is indicative of an acid stain.  If vomitus or stomach contents are available, add 10% barium chloride. A heavy white precipitate forms which is insoluble on adding 1 ml nitric acid.
PHARMD GURU Page 4 MANAGEMENT:  Management of corrosive injury is primarily directed to prompt and thorough decontamination. Evaluation of burns to the gastrointestinal tract may require upper gastro-intestinal endoscopy. Following a significant corrosive exposure local and systemic complications need to be considered.  Respiratory distress due to laryngeal oedema should be treated with 100% oxygen and cricothyroidotomy.  Remove all contaminated clothes and irrigate exposed skin copiously with saline. Non-adherent gauze and wrapping may be used. Deep second degree burns may benefit from topical silver sulfadiazine.  Eye injury should be dealt with by retraction of eyelids and prolonged irrigation for at least 15 to 30 minutes with normal saline or lactated Ringer's solution, or tap water if nothing else is available.  Remove all contaminated clothes and irrigate exposed skin copiously with saline. Non-adherent gauze and wrapping may be used. Deep second degree burns may benefit from topical silver sulfadiazine.  Administer antibiotics only if infection occurs. Prophylactic use is not advisable unless corticosteroid therapy is being undertaken.  Since there is often severe pain, powerful analgesics such as morphine may have to be given.  Emergency laparotomy is mandatory if there is perforation or peritonitis. HYDROFLUORIC ACID:  Hydrofluoric acid (HF) is a relatively weak acid with minimal corrosive effects at low concentrations. Tissue damage is primarily related to dissociation of the acid in tissues and combination of free fluoride ions with intracellular divalent cations (calcium and magnesium) resulting in cell death.  It is commonly used in various forms of industry for glass etching, computer silicone chip production, metallurgy and as a cleaning fluid additive. In low