The term caustic is often mistakenly presumed to denote an alkali, while actually it has a much broader meaning and refers to any substance which is corrosive and burning in nature. Obviously this would include apart from alkalis, the more important group comprising acids (inorganic and organic). Table 5.1 lists the common caustic substances encountered in toxicological practice, while Table 5.2 mentions some ubiquitous commercial products containing corrosives.
All caustics are highly injurious locally and produce burns of varying severity and intensity. Three phases have been recognised—
Acute inflammatory phase (upto 7 days): Characterisedby vascular thrombosis and cellular necrosis. The necrotic mucosa sloughs by the 3rd or 4th day, and an ulcer forms.
Latent granulation phase (1 to 2 weeks): The sloughedarea 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.
Chronic cicatrisation phase (after 2 weeks): There isformation of excessive scar tissue around the submucosa and muscularis mucosa resulting in contractures.
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