You are in: eMedicine Specialties > Plastic Surgery > BURNS Burns, ChemicalArticle Last Updated: Jun 18, 2008AUTHOR AND EDITOR INFORMATIONSection 1 of 10
  Author: Richard F Edlich, MD, PhD, Distinguished Professor of Plastic Surgery, Biomedical Engineering and Emergency Medicine, University of Virginia Health Care System; Director of Trauma Prevention, Education, and Research, Trauma Specialists, LLP, Legacy Verified Level I Shock Trauma Center for Children and Adults at Legacy Emanuel Hospital Richard F Edlich is a member of the following medical societies: Alpha Omega Alpha, American Association of Plastic Surgeons, American Burn Association, American College of Emergency Physicians, American College of Surgeons, American Society of Plastic and Reconstructive Surgery, American Spinal Injury Association, American Surgical Association, American Trauma Society, Plastic Surgery Research Council, Society of University Surgeons, and Surgical Infection Society Coauthor(s): David B Drake, MD, Associate Professor with Tenure, Department of Plastic and Maxillofacial Surgery, Medical Director, DeCamp Burn and Wound Center, University of Virginia School of Medicine; William B Long III, MD, FACS, Sections of Trauma Surgery and Cardiothoracic Surgery, Legacy Emanuel Hospital, Portland, Oregon Editors: Dennis P Orgill, MD, PhD, Associate Professor, Harvard Medical School; Director, Burn Center, Brigham and Women's Hospital; Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine; Wayne Stadelmann, MD, Stadelmann Plastic Surgery, PC; Nicolas (Nick) G Slenkovich, MD, Practice Director, Colorado Plastic Surgery Center at Swedish Medical Center; Lars M Vistnes, MD, FRCSC, FACS, Professor of Surgery, Emeritus, Stanford University Medical Center Author and Editor Disclosure Synonyms and related keywords: chemical burns, chemical injuries, acid, alkali, hydrofluoric acid, formic acid, anhydrous ammonia, cement, phenol, chemical agents, white phosphorus, elemental metals, nitrates, hydrocarbons, tar, Superfund Amendments and Reauthorization Act, SARA, hazardous materials, HAZMAT, Nation Fire Protection Association, emergency medical examination gloves, powder-free gloves, latex-free gloves, ingestion of caustic agents, esophageal stenosis, antral stenosis INTRODUCTIONSection 2 of 10
  Chemical injuries are commonly encountered following exposure to acids and alkali, including hydrofluoric acid (HF), formic acid, anhydrous ammonia, cement, and phenol. Other specific chemical agents that cause chemical burns include white phosphorus, elemental metals, nitrates, hydrocarbons, and tar. Since World War II, the number of chemicals developed, produced, and used in the United States has increased dramatically. More than 65,000 chemicals are available on the market, and an estimated 60,000 new chemicals are produced each year. Unfortunately, the potential deleterious effects on human health of many of these chemicals are unknown. The Superfund Amendments and Reauthorization Act (SARA) contains extensive provisions for emergency planning and the rights of communities to be informed of toxic chemical releases.1 In addition to individualized state health departments, the following 5 national sources provide information regarding death and injuries caused by chemical releases: National Response Center (NRC), Department of Transportation (DOT), Hazardous Materials Information System (HMIS), Acute Hazardous Events (AHE) Database, and American Poison Control Centers Association.2 Health departments from 5 states (Colorado, Iowa, Michigan, New Hampshire, and Wisconsin) evaluated 3,125 emergency chemical-release events involving 4,034 hazardous substances that occurred from 1990-1992. Of these events, 77% involved stationary facilities and 23% were transportation-related. In 88% of events, a single chemical was released. The most commonly released hazardous substances were volatile organic compounds (18%), herbicides (15%), acids (14%), and ammonia (11%). These events resulted in 1,446 injuries and 11 deaths. Respiratory irritation (37%) and eye irritation (23%) were the most commonly reported symptoms. Chemical exposures also can occur at home or as the result of an attack. Many common products once believed to be innocuous (eg, cement, gasoline) are now regarded as potentially hazardous and as the cause of serious injury and illness. Exposure to these agents can be reduced significantly through educational programs, cautionary labeling of toxic products, and appropriate use of protective clothing. When poison control centers identify new products that are toxic to skin, information is added to the regional poison information system to ensure that injured patients are given the benefit of new data. Concomitantly, this information is shared with the manufacturer and Consumer Product Safety Commission (CPSC) to recognize and address the problem nationally. For example, numerous cases of serious permanent injury and, occasionally, death caused by exposure to sulfuric acid drain cleaners have been recorded by the CPSC. As a result of this alarming problem, the CPSC currently proposes banning the sale of this product to consumers. For excellent patient education resources, visit eMedicine's Burns Center. Also, see eMedicine's patient education articles Chemical Burns and Thermal (Heat or Fire) Burns. PATHOPHYSIOLOGYSection 3 of 10
Most chemical agents damage the skin by producing a chemical reaction rather than hyperthermic injury. Although some chemicals produce considerable heat as the result of an exothermic reaction when they come into contact with water, their ability to produce direct chemical changes on the skin accounts for most significant injury. Specific chemical changes depend on the agent, including acids, alkalis, corrosives, oxidizing and reducing agents, desiccants and vesicants, and protoplasmic poisons. The concentration of toxic agent and duration of its contact primarily determine the degree of skin destruction. When the skin is exposed to toxic chemicals, its keratinous covering is destroyed, and underlying dermal tissues are exposed to continuous necrotizing action. Both inorganic and organic acids denature the proteins of the skin, resulting in a coagulum, the color of which depends on the acid involved. Nitric acid burns result in a yellow eschar, whereas sulfuric acid eschar is black or brown. Burns caused by hydrochloric acid or phenol tend to range from white to grayish-brown. Following the initial exposure, cellular dehydration and further protein denaturation/coagulation occur. This dehydrative effect results in the characteristic dry surface of acid burns. The method(s) of neutralization used in the treatment of acid burns depend on the nature of the acid. Alkali burns are those caused by lime (cement), ammonia, and caustics (sodium hydroxide, potassium hydroxide). Alkali dissolves protein and collagen, resulting in alkaline complexes of these molecules. Cellular dehydration (as in acid burns) and saponification of fatty tissue also occurs. Whereas acid burns are characterized as "dry" burns, with little fluid loss or edema, alkali burns present with marked edema and extensive fluid loss. Neutralization of alkali exposure is accomplished by first irrigating the burned site with a large amount of water to dilute any unreacted alkali remaining on the wound surface. This protects the wound from further damage caused by heat released during the neutralization reaction. After skin contact, absorption of some agents may cause systemic toxicity. Dichromate poisoning produces liver failure, acute tubular necrosis, and death. Oxalic acid and HF injuries may result in hypocalcemia. Tannic and phosphorous burns may be followed by nephrotoxicity. Absorption of phenol may be associated with CNS depression and hypotension. Inhalation injury may result from exposure to toxic fumes, particularly when the exposure occurs within a closed space. COMMUNITY PREPAREDNESS AND HAZMAT RESPONSESection 4 of 10
Hazardous materials (HAZMAT) are substances that may injure life and damage environment if improperly handled. These substances can be encountered in the home, in urban (industrial) areas, in rural (agricultural) areas, or anywhere involving the release of hazardous material. HAZMAT accidents are particularly dangerous for responding personnel, who are in danger of exposure from the time of arrival on the scene until containment of the accident. The surrounding community also is commonly endangered. The Superfund Amendment and Reauthorization Act (SARA) mandates community preparedness for dealing with HAZMAT accidents.1 Before a community develops its plans for responding to HAZMAT accidents, it needs to determine what types of materials are likely to be involved. For those exposed to potentially dangerous chemicals at home, it is best to remove the chemical from the anatomic site by irrigation with copious amounts of water. A friend or relative must then telephone the regional poison control center certified by the American Association of Poison Control Centers.3, 4 If the chemical is judged dangerous, make arrangements to transfer the exposed person to the nearest emergency department (ED) for definitive care. Notify the ED as soon as possible after the accident to allow staff to prepare to receive the patient. Identify and assess hazardous environment Paramedics and members of the HAZMAT response team (usually firefighters) must work together to identify toxic chemicals and assess hazardous environments. Placards, shipping papers, United Nations chemical identification numbers, and markings on shipping containers help identify hazardous agents. In some cases, members of the HAZMAT team may have to use chemical analysis to identify the agent. The presence of carbon monoxide, cyanide, hydrogen sulfide, oxygen, and combustible gases can be detected using different instruments. Colorimetric detector tubes can approximate the concentrations of chemicals in the air. Alpha, beta, and gamma radiation detectors can record radioactive contamination. Contacting the 24-hour hotline of Chemtrec (Chemical Manufacturers Association, Contingency plan The contingency plan for HAZMAT management can be divided into 2 parts: initiation of the site plan and evacuation. Initiation of the site plan begins after identifying HAZMAT and assessing the surrounding environment. Once HAZMAT is identified, determine health risks to the environment. A command post away from the exposure site is essential to a large incident involving HAZMAT, because it allows paramedics, HAZMAT team members, firefighters, police, representatives from state and local government, and manufacturer and shipper to coordinate activities. Coping with HAZMAT incidents In coping with HAZMAT incidents, 2 distinct goals must be achieved concomitantly. First, HAZMAT must be contained, fire and explosions must be extinguished, and the site eventually must be cleaned. Second, those exposed to HAZMAT must be treated. The first priority in the care of people exposed to HAZMAT is decontamination, which is initiated by removing the victim's clothes and isolating them in plastic bags. Liquid chemicals are washed off the victim's body with water, whereas dry chemicals are first brushed off, followed by copious water irrigation delivered under low pressures. Priority of decontamination should progress from cleansing of contaminated wounds to eyes, mucous membranes, skin, and hair. While performing decontamination, conduct a primary and secondary survey of the patient to detect life-threatening injuries and take appropriate steps to stabilize the patient's condition (eg, administer oxygen to dyspneic patients). Ideally, patients should be thoroughly decontaminated before arrival in the ED. Hospital personnel involved in decontamination should wear chemical-resistant clothing with built-in hood and boots, at least 2 layers of gloves, protective eyewear, and some form of respiratory protection. The minimum level of respiratory protection for hospital personnel during decontamination has not been established. ACIDS AND ALKALISection 5 of 10
Chemical burns Chemical burns continue to destroy tissue until the causative agent is inactivated or removed.5 For example, when hydrotherapy is initiated within 1 minute after skin contact with either an acid or alkali, severity of the skin injury is far less than when treatment is delayed for 3 minutes. Early treatment is followed by a return of skin pH to normal. When contact time exceeds 1 hour, the pH level of a sodium hydroxide (NaOH) burn cannot be reversed. Similarly, brief washing of a hydrochloric acid (HCl) burn more than 15 minutes after exposure does not significantly alter acidity of damaged skin. Because contact time is a critical determinant of the severity of injury for skin exposed to a toxic liquid chemical, an exposed person or a witness to the injury must initiate hydrotherapy immediately. When workers' clothes are soaked with such agents, valuable time is lost if their clothing is removed before copious washing commences. Gentle irrigation with a large volume of water under low pressure for a long time dilutes the toxic agent and washes it out of the skin. During hydrotherapy, the rescuer should remove the patient's clothes and wear powder-free, latex-free, emergency medical examination gloves to prevent hand contact with the chemical(s). Hydrotherapy After exposure to strong alkali, prolonged hydrotherapy is especially important to limit severity of injury. In experimental animals, the pH level of chemically burned skin does not approach normal concentration unless more than 1 hour of continuous irrigation has been maintained, and it often does not return to normal for 12 hours despite hydrotherapy. This differs from HCl skin burns, in which the pH level usually returns to normal within 2 hours after initiating hydrotherapy. The mechanism by which NaOH maintains an alkaline pH level despite treatment is related to byproducts of its chemical reaction to skin. Alkalis combine with proteins or fats in tissue to form soluble protein complexes or soaps. These complexes permit passage of hydroxyl ions deep into the tissue, limiting their contact with water diluent on the skin surface. Conversely, acids do not form complexes, and their free hydrogen ions are easily neutralized. Regardless of causative agent, continue hydrotherapy once the patient arrives in the ED. If the chemical is localized in the patient's hand, immerse the injured part in a sink under flowing tap water. For other anatomic sites, place them supine in a hydrotherapy tank in which the temperature of the water can be regulated. Continue hydrotherapy treatment for 2-3 hours for acid burns and for at least 12 hours for strong alkali burns. When the patient's clothing comes in contact with solid chemical (eg, lye), remove contaminated clothing before instituting hydrotherapy. Remove all visible solid particles from the patient's skin during copious irrigation with water. Deliver water to the wound at the lowest possible pressure, because high-pressure irrigation (shower) may disperse liquid or solid chemical into the patient's or rescuer's eyes. Water is the agent of choice Water is the agent of choice for decontaminating acid and alkali skin burns. Deleterious effects of attempting to neutralize acid and alkali burns were first noted in experimental animals in 1927.7 In every instance, animals with alkali or acid burns that were washed with water survived longer than animals treated with chemical neutralizers. The additional trauma of the heat generated by the neutralization reaction superimposed on the already existing burn accounts for the striking difference between the results of these 2 treatment methods. The same effect may occur when certain chemicals contact water, yet large volumes of water tend to limit this exothermic reaction. Surgeons are beginning to question the belief that neutralization of an alkaline burn of the skin with acid does, indeed, increase tissue damage due to the exothermic nature of acid-based reactions.8 In experimental studies in animals, surgeons demonstrated that topical treatment of alkaline burns with a weak acid such as 5% acetic acid (ie, household vinegar) resulted in rapid tissue neutralization and reduction of tissue injury in comparison to water irrigation alone. The observed benefits of treating alkaline burns with 5% acetic acid in the rat model are significant and require clinical testing. Treating acid and alkali eye injuries Acid and alkali injuries involving the eye are among the most disastrous of chemical burns.9 Regardless of the nature of chemical involved, the primary goal is to immediately institute copious irrigation. At the scene of the injury, the exposed person should submerge his or her eyes in a container of tap water and continuously open and close them. In the absence of a container, hold face and eyes beneath a faucet and continuously irrigate with water. If possible, maintain irrigation during transport to hospital. In the ED, subject the eye to immediate hydrotherapy. This is most easily accomplished using a low-flow stream of 0.9% NaCl from intravenous (IV) tubing. The patient's response to chemical spillage into the eye can frustrate emergency treatment: responses include severe blepharospasm, tearing, and forceful rubbing of the eye. Topical anesthetic agents help limit pain and improve patient cooperation. Lid retractors may be necessary to evert eyelids and ensure adequate evaluation and irrigation of conjunctival sac. First, remove any foreign material or solid chemical. Continue irrigation until the pH level of the conjunctival sac returns to its physiologic level (pH 7.4). Monitor the pH level of the conjunctival sac with a Ninhydrin reagent strip. Compare the pH levels of the affected and unaffected eye. After irrigation, stain eyes with fluorescein to detect corneal injury. Then perform slit-lamp examination of the eye with corneal injury to determine the extent of damage to the anterior segment of the eye and anterior third of the vitreous chamber. Initial slit-lamp examination of alkali burn often reveals corneal erosion, swelling of the corneal epithelium, and clouding of the anterior chamber. Treat all eyes that demonstrate corneal abrasion with a broad-spectrum antibiotic emollient instilled in the conjunctival sac (eg, chloramphenicol, gentamicin). Ophthalmologic consultation and close follow-up care are warranted in all significant exposures, and hospitalization for continuous irrigation occasionally may be required. (For more information, see eMedicine Ophthalmology article Burns, Chemical.) Measure intraocular pressure serially to detect pressure increases. Occasionally treat the injured eye with long-acting cycloplegic, mydriatic, and carbonic anhydrase inhibitor for 2 weeks or until pain disappears. This treatment decreases the potential for pupillary constriction, increased intraocular pressure, and early glaucoma. (For more information, visit Medscape's Ocular chemical injury remains one of the most difficult ocular emergencies. The prognosis for a burned eye depends not only on the severity of the injury, but also on the rapidity and mode of treatment. Recently, amniotic membrane patching (AMP) has been demonstrated to be useful toward achieving a desirable outcome for acute ocular chemical burns. The human placenta was obtained shortly after elective caesarean delivery from a donor mother. Human immunodeficiency virus, hepatitis virus type B, hepatitis virus type C, and syphilis were serologically excluded. Temporary AMP with modifications in suture placement was performed in patients inflicted with acute chemical injury. Clinical results suggest that immediate AMP is quite useful for managing moderately severe acute ocular chemical injury by facilitating rapid epithelialization and pain relief and by securing ocular surface integrity. Effects of alkali burns Alkali substances are the most toxic chemicals, and anhydrous ammonia appears to be the worst offender. Even alkali burns that seem mild can result in devastating injury, because alkalis tend to react with the lipid in corneal epithelial cells to form soluble soap that penetrates corneal stroma. Alkali moves rapidly through the stroma and endothelial cells to enter the anterior chamber. Anhydrous ammonia can penetrate the anterior chamber in less than 1 minute. Alkali usually kills each tissue layer of the anterior segment of the eye that it contacts. This results in occlusive vasculitis around the corneoscleral limbus, which makes repair of these tissues difficult. As the tissues of the anterior segment of the eye degenerate, perforation follows with the development of endophthalmitis and loss of the eye. If perforation can be prevented, recovery of sight may be possible through eventual corneal transplantation. Recent experimental studies conclude that destruction of corneal stroma can be minimized by drug therapy (eg, N-acetylcysteine, steroids). However, drug therapy has limited therapeutic usefulness because of the need for frequent applications, significant number of clinical failures, and potential adverse effects. Management of ingested alkali Eyes tolerate acid burns better because like other living tissue, they have significant acid-buffering capacity. Tear film, the proteins present in tears, and conjunctival epithelial cells rapidly neutralize acid. Consequently, acid typically causes epithelial and basement membrane damage, yet rarely damages deep endothelial cells. Acid burns that injure the periphery of the cornea and conjunctiva often heal uneventfully, leaving a clear corneal epithelium. In contrast, acid burns of the central part of the cornea may lead to corneal ulcer formation with neovascularization and scarring, requiring later reconstruction. Hydrofluoric AcidDuring 1985 and 1986, the American Association of Poison Control Centers Data Collection System received 2367 reports of human exposures to hydrofluoric acid (HF).12, 13 Four fatalities occurred, three from ingestion and one as a result of dermal exposure. Significant local and systemic toxicity can result from exposure of eye, skin, or lung to HF.HF is one of the strongest inorganic acids. Its use is mainly industrial, involving glass etching, metal cleaning, electronic industries, and biochemical laboratories. However, it can also be found in households as a component of rust removers and aluminum-cleaning products. Because of these numerous applications, there is a large risk for accidental human exposure to HF. In the United States, more than 1000 incidents of accidental exposures to HF are reported annually. The risk and potential toxicity associated with such exposure are often underestimated by persons handling this liquid in households, laboratories, and industrial plants. Significant local and systemic toxicity can result from exposures of the eyes, skin, or lungs to HF. Inhalation of HF vapor is rare and usually involves explosions that produce fumes or high concentrations of liquid HF (>50%) that soak the clothing of the upper body. Patient outcomes vary considerably depending on concentration and duration of exposure to HF. Inhalation and skin exposure to 70% HF has caused pulmonary edema and death within 2 hours. Pulmonary injuries that are not evident until several days after exposure also can occur. The patient has no respiratory symptoms and a normal chest radiograph initially, yet massive purulent tracheobronchitis that is refractory to treatment may develop. Respiratory symptoms may persist for months after inhalation of HF fumes. Sustained irritation of the larynx and pharynx with fibrinous, granulating deposits on thickened vocal cords may cause persistent cough and hoarseness. Management of exposure to HF Management of inhalation exposure involves removing the patient from the source, then decontaminating clothes and skin.14, 15 If respiratory symptoms are present, monitor the patient with pulse oximetry, administer humidified oxygen using a nonrebreathing reservoir bag mask system, and evaluate him or her for laryngeal edema, pneumonitis, pulmonary edema, pulmonary hemorrhage, and systemic toxicity. Treatment of HF inhalation injury is primarily symptomatic. Administration of 2.5-3% calcium gluconate solution by nebulizer as therapy for inhalation of HF has been suggested but not tested. Admit asymptomatic patients with possible HF inhalation for observation. Eye exposure to HF vapors produces more extensive damage than that of other acids at similar concentration. The extent of damage by HF depends on its concentration. Exposure of rabbits to 0.5% HF causes mild initial conjunctival ischemia that resolves in 10 days; 8% HF causes severe initial ischemia that is still noted after 65 days. Corneal opacification and necrosis occur after exposure to 20% HF. Irrigation therapy for HF Initiate immediate and copious irrigation of the exposed eyes at the scene of exposure and continue for at least 30 minutes during transport to the ED, where an ophthalmologic examination can be performed promptly. Local ophthalmic anesthetic drops enhance patient comfort and cooperation during irrigation and evaluation. In experimental animals, single irrigations with 1 L of water, isotonic saline, or magnesium chloride are the only treatments that are therapeutically beneficial without causing toxicity. Benefits include decreased epithelial loss and reduced corneal inflammation. Repeated irrigations over time have no therapeutic merit and are associated with an increased occurrence of corneal ulceration. Patients with significant ocular exposure to HF should be seen emergently by an ophthalmologist. HF skin exposures A large number of personnel in industry and research handle concentrated solutions of HF. Relatively dilute solutions of HF (0.6-12%) are available to the public in the form of rust removal and aluminum cleaning products. During handling of containers holding HF, inadvertent contamination of unprotected fingers and hands often occurs, resulting in chemical burn injury. HF skin burns have certain distinct characteristics. First, exposure causes progressive tissue destruction associated with intense pain that can be delayed in onset for hours and can persist for days if untreated. Skin at the site of contact develops a tough, coagulated appearance. Untreated sites progress to indurated, whitish, and blistered vesicles that contain caseous, necrotic tissue. In exposure of the digits, HF has a predilection for subungual tissue. Severe untreated burns may progress to full-thickness burns and may even result in loss of digits. Treatment of HF skin exposure Initial treatment of HF skin exposure is immediate irrigation with copious amounts of water or a saturated solution of sodium bicarbonate for at least 15-30 minutes. Most exposures to dilute solutions of HF respond favorably to immediate irrigation. Severe pain or any pain that persists after irrigation denotes a more severe burn that requires detoxification of fluoride ion by promoting the formation of an insoluble calcium salt. Remove all blisters first because necrotic tissue may harbor fluoride ions. Then detoxify fluoride ion through topical treatment, local infiltrative therapy, or intra-arterial infusion of calcium. Calcium gluconate (2.5%) gel is the preferred topical agent. Because skin is impermeable to calcium, topical treatment is effective only for mild, superficial burns. Because this gel is not stocked in most hospital pharmacies, it must be formulated by mixing 3.5 g of calcium gluconate powder in 150 mL of water-soluble lubricant (eg, K-Y Jelly). An occlusive cover (eg, latex glove) should secure the gel. Infiltrative therapy for HF burns Infiltrative therapy is necessary to adequately treat deep and painful HF burns. Calcium gluconate is the agent of choice and can be administered either by direct infiltration or intra-arterial injection.
Despite its wide acceptance, the infiltration technique has notable disadvantages, especially when treating digits. A regional nerve block is recommended because injections may be very painful. Removal of the nail to expose the nail bed is required if subungual tissue is involved. Vascular compromise can occur if excessive fluid is injected into skin exposure sites, and unbound calcium ions have a direct toxic effect on tissue. Despite these disadvantages, intra-arterial infusion of calcium is gaining popularity.
HF action HF binds calcium and magnesium with strong affinity. Systemic fluoride toxicity, including dysrhythmias and hypocalcemia, can occur from ingestion, inhalation, or dermal exposure to HF. Consequently, all patients with significant HF exposure should be hospitalized and monitored for cardiac dysrhythmias and electrolyte status for 24-48 hours. Hypocalcemia can occur after significant exposures to HF and should be corrected with 10% calcium gluconate administered intravenously. If left untreated, a burn caused by 7 mL of 99% HF can theoretically bind all available calcium in a 70-kg man. Prolonged QT interval on electrocardiogram is a reliable indicator of hypocalcemia. Formic AcidFormic acid is a caustic organic acid used in industry and agriculture.16, 17, 18 It causes cutaneous injury by coagulation necrosis. Systemic toxicity occurs after absorption and manifests as acidosis, hemolysis, and hemoglobinuria. Hemolysis is the result of the direct effect of formic acid on red blood cells. Institute copious wound lavage immediately. Treat acidosis with sodium bicarbonate. Mannitol may be used to expand plasma volume and promote osmotic diuresis in patients with hemolysis. Exchange transfusions and hemodialysis may be needed in patients with severe formic acid poisoning. Anhydrous AmmoniaAmmonia is used in the manufacture of explosives, petroleum, cyanide, plastic, and synthetic fibers.19 In addition, it is widely used as a cleaning agent and as a coolant in refrigerator units. As an agricultural fertilizer, ammonia is ideal because of its high nitrogen content (82%). Sudden release of liquid ammonia can cause injury through two different mechanisms. It has an extremely low temperature (-33° C) and freezes any tissue it contacts. Ammonia vapors readily dissolve in the moisture of skin, eyes, oropharynx, and lungs to form hydroxyl ions, which cause chemical burns through liquefaction necrosis. The severity of injury directly relates to the concentration and duration of exposure to ammonia. Irrigation for anhydrous ammonia injury Treatment consists of prompt irrigation of eyes and skin with water and management of inhalation injury. If necessary, secure the airway by nasal or oral intubation. Use a large diameter tube to prevent distal airway obstruction from sloughing of mucosa. After intubation, manage lower airway injury with positive end expiratory pressure (PEEP) ventilation. CementCement burns are alkali burns.20 When dry cement is combined with water, hydrolysis occurs. Resulting mixture is essentially a solution of slated lime saturated in water with an initial pH of 10-12. As hydrolysis continues, the pH level may continue to rise to 12 or 14, which is comparable to that of sodium, potassium hydroxide, or lye. In addition, contact dermatitis from chromate (a trace element) has been reported. Treatment of cement burns The best treatment of cement burns is immediate copious irrigation until the substance is completely gone, a practice performed by experienced workers who habitually wash off cement throughout the day. Prominent warning labels on packages containing cement products direct the user to wear protective gloves when using the product in either its wet or dry state. Cement burns of the lower extremities respond well to immediate copious irrigation followed by coverage with a medicated bandage (eg, Gelocast Unna boot) that allows patient to ambulate. Phenol and its DerivativesPhenols are used industrially as starting materials for many organic polymers and plastics. They are used widely in agricultural, cosmetic, and medical fields. Because of their antiseptic properties (first appreciated by Lister), they are used commonly in many commercially available germicidal solutions. A number of phenol derivatives (eg, hexylresorcinol, resorcinol) are more bactericidal than phenol itself. Chemical peels Plastic surgeons use dilute solutions of phenol for chemical facial peels.21 Phenol (which is usually mixed with water, soap, and croton oil for this application) can produce a partial-thickness burn of predictable depth in a controlled manner. It has been the standard for many years for new technologies in skin resurfacing to remove both coarse and fine wrinkles, irregular facial pigmentation, and actinic keratoses. The concentration of phenol is kept sufficiently low to reduce the occurrence of systemic complications. Interestingly, higher concentrations of phenol result in a shallower burn depth. A higher concentration of phenol results in increased coagulation of the keratin in the skin, thus forming a barrier to further penetration. Histologic studies have demonstrated that 100% concentrations of phenol produce 35-50% less penetration than a 50% phenol solution. The physician performing phenol chemical peels should be concerned about the possibility of rapid phenol absorption. When phenol is applied to more than 50% of the facial surface in less than 30 minutes, a high incidence of cardiac arrhythmias is reported. When the application time over the same area was increased to 60 minutes, arrhythmias were avoided. Because of the complication of cardiac arrhythmias, all patients undergoing phenol peeling should be monitored electrocardiographically and have an intravenous line in place. Following application of the phenol solution, the skin is covered with an occlusive dressing that consists either of multiple layers of waterproof tape or petroleum jelly to prevent evaporation of the phenol, allowing for increased penetration and burn depth. The peeled skin is maintained by daily cleansing and consequent reapplication of ointment, which keeps the surface moist and prevents desiccation. If this protocol is followed, healing is completed within 5-7 days. Phenol is an aromatic acidic alcohol.22 This compound and its derivatives are highly reactive, corrosive, contact poisons that damage cells by denaturing and precipitating cellular proteins. Their characteristic odor usually signals their presence. After phenol penetrates dermis, it produces necrosis of papillary dermis. This necrotic tissue may temporarily delay its absorption. When skin comes in contact with phenol, institute treatment immediately. Irrigate exposed area with large volumes of water delivered under low pressure. Dilute solutions of phenol are more rapidly absorbed through skin than concentrated ones, thus avoid gentle swabbing of surface of skin with sponges soaked in water. Because phenol may become trapped in the victim's hair or beard, remove any hair that has come into contact with the chemical agent as soon as possible. Symptoms of exposure In animal studies, exposure to as little as 0.625 mg/kg of phenol causes death. In humans, absorbed phenol causes profound CNS depression, resulting in coma and death from respiratory failure. Marked hypotension may occur as a result of central vasomotor depression in addition to a direct effect on the myocardium and small blood vessels. Phenol also is a powerful antipyretic that produces a fall in body temperature. Metabolic acidosis may result from shock as well as from the direct effect of acidic phenol. A number of substituted phenols (eg, resorcinol, picric acid) have systemic actions distinct from that of phenol. Stimulation of CNS is commonly encountered after absorption of resorcinol. Picric acid hemolyzes RBCs and causes acute hemorrhagic glomerulonephritis and acute liver injury. Treatment of phenol exposure Experimental studies indicate that water alone is effective in reducing the severity of burns and preventing death in animals with skin exposed to phenol and its derivatives. The most effective treatment is undiluted 200-400 molecular weight polyethylene glycol (PEG) or isopropanol. This material should be stocked in hospitals located near areas of phenol use. Often, it can be located in the chemical section of hospital pharmacies. A quick wipe of the skin with PEG solution reduces mortality and burn severity in experimental animals. These solutions can be used in phenol burns of the face because they are not irritating to eyes. Decontaminate with water until the PEG solution is obtained. Use large amounts of water because small amounts are detrimental, enhancing dermal absorption of phenol. Remove phenol in a well-ventilated room to avoid exposing hospital personnel to high concentrations of phenol fumes. Treatment of systemic symptoms is purely symptomatic. Respiratory depression may require ventilatory support. Treat hypotension with isotonic crystalloid fluid and pressor agents as needed. Metabolic acidosis may require treatment with sodium bicarbonate. Alkalinization also prevents the precipitation of hemoglobin in urine that occurs with hemolysis. Administering mannitol intravenously, which causes osmotic diuresis, can enhance hemochromogen excretion in urine. Anticonvulsants may be required to treat seizures resulting from CNS stimulation. ELEMENTSSection 6 of 10
White PhosphorusWhite phosphorus is a yellow, waxy, translucent solid element that burns in air unless preserved in oil. When it ignites spontaneously in air, it is oxidized to phosphorous pentoside, which forms metaphosphoric and orthophosphoric acids with addition of water. Phosphorus can ignite spontaneously in air at temperatures higher than 34°C; this has encouraged its use as an incendiary agent in military weapons and fireworks. After explosion of phosphorous munition, flaming droplets may become embedded beneath skin, where they oxidize adjacent tissue unless removed. In nonmilitary industry, white phosphorus is used in the manufacture of insecticides, rodent poisons, and fertilizers. Tissue injury Tissue injury from exposure to white phosphorous appears to be caused primarily by heat production, rather than by liberation of inorganic acids or cellular dehydration by hygroscopic phosphorous pentoside. The ultimate result of this thermal injury is often a painful partial or full-thickness burn. Prehospital care Prehospital care should include immediate removal of contaminated clothing followed by submersion of phosphorus-contacted skin in cool water. Avoid warm water because white phosphorous becomes liquid at 44° C. Remove phosphorus particles from victim's skin and submerge in water. Cover burned skin with towels soaked in cool water during transport to the ED. Treatment of white phosphorus burns After the patient's arrival in the ED, wash burned skin with a suspension of 5% sodium bicarbonate and 3% copper sulfate in 1% hydroxyethyl cellulose.23, 24 (This mixture must be made by hospital pharmacies.) Phosphorus particles become coated with black cupric phosphide, allowing for easy identification. Copper sulfate also decreases the rate of oxidation of phosphorus particles, limiting their damage to underlying tissue. Since blackened particles can still elicit tissue injury, they should be removed. If absorbed systemically, copper sulfate is toxic. Absorption of copper sulfate can be minimized by surface-active agent in the aforementioned suspension, as well as by sodium lauryl sulfate. Before the advent of these agents, prolonged treatment of phosphorus burns with copper sulfate solutions led to systemic copper poisoning, which manifests as vomiting, diarrhea, hemolysis, oliguria, hematuria, hepatic necrosis, and cardiopulmonary collapse. After subjecting burned skin to a suspension of copper sulfate for 30 minutes, thoroughly wash the antidote from the skin. Washing limits the development of systemic copper toxicity. An alternative approach is to use a Wood lamp to identify phosphorus particles because they fluoresce under ultraviolet light. Metabolic derangements have been identified in white phosphorous burns. Postburn serum electrolyte changes consist of depression of serum calcium and elevation of serum phosphorus. Also identified are postburn ECG abnormalities, including prolongation of QT interval, bradycardia, and ST-T wave changes. These ECG changes may explain early sudden death occasionally seen in patients with apparently inconsequential white phosphorous burns. After hydrotherapy and treatment with appropriate antidote, definitively manage skin burns in the hospital intensive care unit setting as with any other burn wound. Elemental MetalsElemental metals (sodium, potassium) are harmless unless activated by water, which causes an exothermic reaction with the release of heat and generation of hydrogen gas and hydroxide.25 Evolved heat is sufficient to ignite hydrogen gas, which results in even greater heat and causes additional thermal burns. Furthermore, formation of hydroxide compound may result in significant chemical injury to tissue. Reaction occurs more rapidly with elemental potassium than with sodium. These deleterious effects of potassium have been attributed to trace amounts of potassium superoxide released on exposure to room air. Therefore, water lavage is dangerous in these circumstances. In the prehospital setting, use only a class D fire extinguisher (containing sodium chloride, sodium carbonate, or graphite base) or sand to suppress flames. When the fire is extinguished, metal is covered by oil (eg, mineral oil, cooking oil) to isolate metal from water. Transport the patient to the ED for wound debridement and cleansing. Remove small pieces of metal from the skin. Place sodium fragments in isopropyl alcohol containing no more than 2% water; insert potassium particles into tertbutyl alcohol for safe deposit. NITRATESSection 7 of 10
Toxic methemoglobinemia is a well-recognized hazard of ingestion of nitrates and nitrites.26 Occasionally, severe methemoglobinemia has been reported in patients sustaining burn injury from molten sodium and potassium nitrates. In these patients, methemoglobinemia is caused by absorption of nitrates through burned skin. Diagnosis of methemoglobinemia should be sought in a cyanotic patient who is unresponsive to oxygen therapy and whose blood appears chocolate brown. Methemoglobin levels lower than 20-30% usually are asymptomatic and require no treatment. Levels higher than 30%, with or without symptoms, should be treated with high-flow oxygen and intravenous methylene blue administered slowly at dose of 1-2 mg/kg body weight. Exchange transfusions also may benefit severe cases by rapidly decreasing circulating methemoglobin concentration. HYDROCARBONSSection 8 of 10
Cutaneous injury from immersion in gasoline and other hydrocarbons may occur in individuals involved in motor vehicle accidents.27 Solvent properties of hydrocarbons cause cell membrane injury and dissolution of lipids, resulting in skin necrosis. Although full-thickness injuries can occur, most injuries are partial thickness. Once gasoline damages the protective skin barrier, hydrocarbons are absorbed. This produces systemic toxicity leading to neurologic, pulmonary, cardiovascular, GI, and hepatic injuries. Treatment of individuals exposed to gasoline includes immediate removal from site of exposure, removal of all clothing, copious irrigation, and transfer to the ED while continuing copious irrigation. Management in the ED consists of wound care of burn injuries and a search for evidence of systemic toxicity. TARSection 9 of 10
Burns from hot tar are a challenging clinical problem.28, 29 Hot liquified tar that contacts skin transfers heat to cause burn injury. Tar then cools and solidifies on the skin surface, making removal difficult. Hot tar includes two distinct groups of materials: coal tar pitches and petroleum-derived asphalts. Both products are heated to maintain liquid form. Paving roads requires tar temperatures from 275-300°F, while roofing demands higher tar temperatures of 450-500°F. Deeper burn injuries are associated with burns from roofing asphalt. Mechanisms of injury include cauldron explosion, falling from buildings, trucks rolling over, pipe explosion, spillage from buckets, and industrial accidents. Prehospital treatment When hot tar contacts skin, it rapidly cools, solidifies, and becomes enmeshed in the hair. It is important to facilitate this cooling process by adding cold water to the tar at the scene of the accident. Cooling tar with cold water limits the amount of tissue damage and prevents the spread of tar. Tar should be continually washed with water until it has cooled and hardened. After cooling, dry skin with towels to prevent systemic hypothermia. Do not remove adherent tar at the scene of the accident. In the ED, definitive care of tar burn injury involves early removal of tar, because it occludes injured skin and encourages bacterial growth. This can convert a partial-thickness burn to a full-thickness burn. Tar adheres to skin because it is enmeshed in the hair, not because of a direct bond between epidermis and tar. Treatment to remove tar Solvents used to remove tar ideally should have close structural affinity to tar. Asphalts are susceptible to both aromatic (eg, naphthalene) and aliphatic (eg, hexade) hydrocarbon solvents, while coal tars are only susceptible to aromatic hydrocarbons. The cleansing capacity of these solvents is enhanced by prolonged contact with tar. Broad-spectrum antibiotic ointments such as bacitracin (400 U/g), polymyxin B (5000 U/g), and neomycin (5 mg/g) may be added to lower the incidence of infection. Remove antimicrobial petrolatum ointments and reapply every hour until all tar is removed. The process of tar removal usually takes 12-48 hours. Antibiotic ointment has been used successfully to remove even tar layered over corneas and conjunctivas. An alternative to petrolatum ointments is surface-active agents, such as polyoxyethylene sorbitan (Tween 80) and polysorbate (De-Solv-It). These are more water soluble and more easily removed from skin with water than petrolatum ointments. These surface-active agents are an effective, safe, and inexpensive means of removing tar from skin. NISA baby oil, sunflower oil, and butter also have been used to remove adherent tar from skin, taking from 30-90 minutes for complete removal. Sunflower oil has proven effective and safe in removing tar without inflicting further skin damage. REFERENCESSection 10 of 10
Article Last Updated: Jun 18, 2008 |
