The dead tissues over the surface of a burn have to separate. If the burn is superficial, they peel off as pieces of dry membrane. If it is deep, they either form: (1) a slough, which is moist, soft, grey, and stinking. Or, (2) they form an eschar which is dry, hard, and dark and which may be so brittle that it cracks. There is no sharp distinction between sloughs and eschars, the main difference being how dry or how wet they are. The exposure method tends to form eschars, while the occlusive and saline methods form sloughs. Pieces of slough and eschar can: (1) Fall off spontaneously, if you wait long enough for infection to rot them. Even burnt bone will sequestrate eventually. (2) Come off in small pieces in the dressings of the occlusive method. (3) Be removed by escharotomy or ’sloughectomy’ in the theatre. However sloughs and eschars separate, they leave wet granulations underneath them, which you must graft. Maggots also deslough most effectively, although few people have the courage to use them deliberately.
Sloughs and eschars have three dangers: (1) Eschars (but not sloughs), may restrict the circulation. Both eschars and sloughs may, (2) become infected, or (3) cause severe bleeding when you remove them, especially if you remove them from a large area.
A thick, tough, dry eschar can act like a tourniquet, and may constrict a patient’s neck, or his chest, or the circulation in his limbs or his fingers. His oedematous tissue swells, but the eschar round it is rigid and cannot expand. Escharotomy can thus be an emergency procedure.
If only a patient’s skin is dry and dead, the underlying tissues can remain uninfected for several weeks, during which the patient’s fat liquefies. But if muscle is dead, infection occurs much more easily, and a rise in temperature about the 10th day usually shows that it has started. Infection under an eschar is difficult to localize, but pain is a useful sign. When infection is further advanced, you may be able to feel a dry eschar floating in a pool of pus. If there is much dead muscle, beware of anaerobic infection, particularly gas gangrene and tetanus, and deslough early.
Manipulating any infected tissue may cause bacteraemia, and removing an extensive slough or eschar may shower so many bacteria into a patient’s circulation that it causes septic shock (53.4). So, if a burn is severely infected, deslough it under antibiotic cover. Usually, this is not necessary.
Sloughs and particularly eschars don’t usually bleed until you try to remove them. Then they may bleed massively, especially if the area is large. So remove them a little at a time, in stages separated by a day or two. Remove them gently, and stop when the patient has had enough. Be guided in how much to remove by his pulse and blood pressure, and by the amount of blood he loses.
After you have removed a slough, you can either graft the raw area immediately, if the surface is suitable, or you can wait until there are favourable granulations. Control infection first.
Desloughing can vary from a minor procedure, if a burn is small, to an extensive ’sloughectomy’ in the theatre, if it is large and deep. Most desloughing is done piecemeal by the nurses as they dress a wound, especially when they apply saline soaks. One of the commonest mistakes is not to deslough a burn—as long as any slough remains, you cannot graft it.