INTRODUCTION	Section 2 of 11
Author Information Introduction Clinical Differentials Workup Treatment Medication Follow-up Miscellaneous Pictures Bibliography

Background: Caustics and corrosives cause tissue injury by a chemical reaction. The vast majority of caustic chemicals are acidic or alkaline substances that damage tissue by, in the case of a base, accepting a proton, or, in the case of an acid, donating a proton, in an aqueous solution. The pH or pKa of a chemical is a measure of how easily the chemical accepts or donates a proton; these terms determine the strength or likelihood of serious damage with tissue contact. Substances with a pH or pKa less than 2 are strong acids; those with a pH or pKa greater than 12 are strong bases. The severity of tissue injury from acids and bases is determined by the substance's pH or pKa, concentration, duration of contact, and the amount and physical form of the substance ingested.

Pathophysiology: Caustics produce tissue injury by altering the ionized state and structure of molecules and disrupting covalent bonds. In aqueous solutions, the hydronium ion (H⁺) produces the principle toxic effects for acids, whereas the hydroxide ion (OH^-) produces such effects for bases.

Alkaline ingestions

Alkaline ingestions cause tissue injury by liquefactive necrosis (saponification of fats and solubilization of proteins). Cell death occurs from emulsification and disruption of cellular membranes. The hydroxide ion of the base reacts with tissue collagen and causes it to swell and shorten. Small vessel thrombosis and heat production occurs. Tissue injury occurs rapidly; severe injury occurs within minutes of contact. The most severely injured tissues are the squamous epithelial cells of the oropharynx, hypopharynx, and esophagus (the most commonly involved organ). The stomach is involved in only 20% of all alkaline ingestions. Tissue edema occurs immediately and may persist for 48 hours, eventually progressing to airway obstruction. Over time, granulation tissue replaces the necrotic tissue.

Over the next 2-4 weeks, the scar tissue thickens and contracts to form strictures. The incidence of stricture formation primarily depends upon depth of the burn. Superficial burns result in strictures in fewer than 1% of cases; full thickness burns result in strictures in nearly 100% of cases. Severe burns also may be associated with esophageal perforation.

Acid ingestions

Acid ingestions cause tissue injury by coagulation necrosis (desiccation or denaturation of superficial tissue proteins) with the formation of an eschar or coagulum. The squamous epithelium of the pharynx and esophagus are relatively resistant to this type of injury. The esophagus is involved in 6-20% of acid ingestions. The stomach is the most commonly involved organ in an acid ingestion. Emesis is secondary to pyloric and antral spasm. Small bowel exposure occurs in 20% of cases. The eschar sloughs in 3-4 days and granulation tissue fills the defect. Perforation may occur after the third or fourth day as the eschar sloughs. A gastric outlet obstruction may develop as scar tissue contracts over a 2- to 4-week period. Acute complications include gastric and intestinal perforation and upper gastrointestinal hemorrhage. Significant exposures may cause metabolic acidosis, hemolysis, acute renal failure, and death.

Frequency:

• In the US: Ingestions of caustic substances, accidental and intentional, is a common event. Cleaning substances, many of which are potentially caustic agents, account for more than 200,000 exposures per year reported to US poison control centers; caustic substances accounted for more exposures than any other class of agents.

Mortality/Morbidity: The alkali drain cleaners and acidic toilet bowl cleaners are responsible for the most fatalities from corrosive agents.

• Approximately 10% of caustic ingestions result in severe injury requiring treatment.

• Between 1% and 2% of caustic ingestions result in stricture formation.

Race: No predilection exists.

Sex: No predilection exists.

Age:

• Childhood ingestions: Approximately 80% of caustic ingestions occur in children younger than 5 years. Serious solid ingestion is rare because children generally do not swallow the burning particles that adhere to their oropharynx. Liquid ingestions, however, can be quite serious.

• Adult ingestions: Most intentional ingestions occur in adults. Adult exposures have more morbidity than childhood exposures because of significant volume of exposure and the presence of possible co-ingestants. Occupational exposures often are more severe than other exposures because industrial products are concentrated.

	CLINICAL	Section 3 of 11
Author Information Introduction Clinical Differentials Workup Treatment Medication Follow-up Miscellaneous Pictures Bibliography

History: The identity, concentration, pH or pKa, and amount of substance ingested are important. The time, nature of exposure, duration of contact, and any immediate on-scene treatment are important in determining management of toxicity.

• Dyspnea

• Dysphagia

• Oral pain and odynophagia

• Chest pain

• Abdominal pain

• Nausea and vomiting

Physical:

• Impending airway obstruction

• Stridor

• Hoarseness

• Dysphonia or aphonia

• Respiratory distress, tachypnea, hyperpnea

• Oropharyngeal burns: Significant esophageal involvement may occur without the presence of oropharyngeal lesions.

• Drooling

• Subcutaneous air

• Acute peritonitis

• Abdominal guarding

• Rebound tenderness

• Diminished bowel sounds

• Hematemesis

• Physical examination findings may be deceptively unremarkable after a significant acid ingestion, despite the presence of significant tissue necrosis.

Causes:

• Common acid-containing sources

• Toilet bowl cleaning products

• Automotive battery liquid

• Rust removal products

• Metal cleaning products

• Cement cleaning products

• Drain cleaning products

• Soldering flux containing zinc chloride

• Common alkaline-containing sources

• Drain cleaning products

• Ammonia-containing products

• Oven cleaning products

• Swimming pool cleaning products

• Automatic dishwasher detergent

• Hair relaxers

• Clinitest tablets

• Bleaches

• Cement