Eschar

Eschar is a type of necrotic tissue that can develop on severe wounds. It is typically dry, black, firm, and usually adhered to the wound bed and edges. Eschar can occur on  full thickness injuries, which are wounds that extend below the epidermis and dermis. Examples include third degree burns, or stage three and four pressure injuries. Additionally, eschar can be present on some skin rashes associated with infections, such as ecthyma gangrenosum, scrub typhus, rickettsialpox, and anthrax. 

Eschar differs from a scab, which is formed when platelets and fibrinogen form a fibrin mesh, trap red blood cells on surface wounds, and form a clot that dries into a scab. Instead, eschar is formed when slough, or other dead tissue debris, from a full thickness wound dries out and hardens. 

Because eschar and other types of necrotic tissue impede healing, it is broadly recommended that it be removed. The process of tissue death causes growth factors to be inactivated and slows the formation of granulation tissue in the wound bed. When dead tissue dries out and becomes hardened eschar, it causes wound contraction to be physically obstructed and stunts epithelialization.

Research supports that debriding eschar early in the healing process can decrease healing time. In certain wounds, such as circumferential burns, constriction caused by the presence of eschar can also cause compartment syndrome, which is an increase in pressure within a muscle compartment that can ultimately cause muscle and nerve damage. A notable exception to early debridement could be a stable eschar (i.e., an eschar that is dry, adherent, and intact) that is present on a heel or ischemic limb. Due to inherent decreased blood flow to these areas, some experts argue that the benefit of leaving the eschar in place to reduce the risk of infection outweighs the benefits of debriding.

Because of the firm, dry nature of eschar, sharp debridement with a scalpel may be difficult. Other debridement techniques that can be used include surgical, enzymatic or chemical, mechanical, and biological methods. During surgical debridement, the individual is usually placed under anesthesia to remove dead tissue. Enzymatic, or chemical debridement, occurs when a topical enzyme is used on the eschar to break down the necrotic tissue over time. Mechanical debridement can be performed with dressing types designed to soften and remove the eschar, such as wet-to-dry dressings. Other mechanical options include whirlpool baths or pulse lavage. Biological debridement uses sterile maggots to eat away at the dead tissue, while not harming live tissue.