Chemical Burns in Emergency Medicine 

Chemical burns can be caused by acids or bases that come into contact with tissue. Acids are defined as proton donors (H⁺), and bases are defined as proton acceptors (OH^-). Bases also are known as alkalis. Both acids and bases can be defined as caustics, which cause significant tissue damage on contact. The strength of an acid is defined by how easily it gives up the proton; the strength of a base is determined by how avidly it binds the proton. The strength of acids and bases is defined by using the pH scale, which ranges from 1-14 and is logarithmic. A strong acid has a pH of 1, and a strong base has a pH of 14. A pH of 7 is neutral.

Most acids produce a coagulation necrosis by denaturing proteins, forming a coagulum (eg, eschar) that limits the penetration of the acid. Bases typically produce a more severe injury known as liquefaction necrosis. This involves denaturing of proteins as well as saponification of fats, which does not limit tissue penetration. Hydrofluoric acid is somewhat different from other acids in that it produces a liquefaction necrosis.

The severity of the burn is related to a number of factors, including the pH of the agent, the concentration of the agent, the length of the contact time, the volume of the offending agent, and the physical form of the agent. The ingestion of solid pellets of alkaline substances results in prolonged contact time in the stomach, thus, more severe burns. In addition, concentrated forms of some acids and bases generate significant heat when diluted or neutralized, resulting in thermal and caustic injury.

The long-term effect of caustic dermal burns is scarring, and, depending on the site of the burn, scarring can be significant. Ocular burns can result in opacification of the cornea and complete loss of vision. Esophageal and gastric burns can result in stricture formation. An oral burn is shown in the images below.

Frequency

United States

Burns are a common problem seen in the emergency department. There has been a decrease in the number of burns in the United States through 2000, but this appears to have stabilized since. Most burns are only partial thickness and occur on the extremities. Approximately 5% of individuals with burns presenting to the ED require admission.^[1]

In 2008, the American Association of Poison Control Centers (AAPCC) reported 26,596 cases of exposures to acidic substances, 39,741 cases of exposures to alkaline substances, 9,958 cases of peroxide exposures, and 58,892 cases of bleach exposures. During that time, 1,868 cases of exposure to phenols or phenol products were reported.^[2] Chemical injuries account for 2-6% of burn center admissions.^[3]

International

Worldwide, corrosive substances are commonly used for chemical assault. The most common substances used are lye and sulfuric acid.^[4]

Mortality/Morbidity

In the 2008 report of the American Association of Poison Control Centers, exposures to acids and acid-containing products and chemicals resulted in 10 deaths, 83 cases of major toxicity, and 1788 cases of moderate toxicity. Exposures to alkali products and chemicals resulted in 9 deaths, 168 cases of major toxicity, and 2684 cases of moderate toxicity. Exposures to peroxides resulted in no deaths, 9 cases of major toxicity, and 154 cases of moderate toxicity. Exposures to bleaches and hypochlorite-containing products resulted in 2 deaths, 43 cases of major toxicity, and 2016 cases of moderate toxicity. Exposures to phenol-containing products resulted in no deaths, 2 cases of major toxicity, and 70 cases of moderate toxicity.^[2]

Sex

Assaults with caustic chemicals worldwide are more likely to occur against women.^[4]

Age

Adults and children are nearly equally exposed to caustic chemicals. Adults exposed to industrial strength chemicals often suffer more severe burns.