Crushing injury takes many forms. One of the most vulnerable soft tissues is the skin; continuous pressure applied for more than 2 hours can result in ischemia and the development of a pressure ulcer. Pressure ulcers are particularly likely to develop in skin that overlies a bony prominence and is compressed against a firm surface such as a cast, a rigid shoe or brace, or even a firm mattress. Although the initial lesion is closed, when the skin dies, it sloughs and the lesion may become infected.
Another type of crushing injury occurs when a heavy load falls on a limb, rendering it immobile and obstructing the blood flow (venous, arterial, or both) for several hours. The result is a compartment syndrome. If the resulting ischemia lasts for more than 2 hours, it may cause the death of muscle tissue, with associated permanent loss of function. When blood flow is restored to a crushed limb, the necrotic muscle releases myoglobin into the venous circulation. The myoglobin may sludge in the kidneys, producing acute renal failure. The risk of this complication may be minimized by adequate hydration of the patient after a crush injury. Ischemia that persists for a long time leads to gangrene of the entire crushed limb.
OPEN SOFT TISSUE INJURY
Open soft tissue injuries are, by definition, contaminated (see Plate 7-2). The many different types of open soft tissue injuries—abrasion, laceration, avulsion, puncture, degloving, and amputation—are caused by a variety of mechanisms. Regardless of the particular pattern of injury, the common denominators are penetration of the skin and bacterial contamination of the deeper tissues, which establish the potential for infection. Blood loss in open wounds is usually greater than in closed injuries, because the bleeding is not limited by the tamponade effect created by the encompassing soft tissues.
Treatment of open wounds initially focuses on controlling the bleeding and contamination. Pressure should be applied to the wound at once to stop bleeding, and tetanus prophylaxis must be confirmed or provided and in certain situations (e.g., open fracture) antibiotics should be administered. After the bleeding is controlled, all open wounds must be thoroughly debrided to remove as much contaminating material and nonviable tissue as possible. Whenever the adequacy of the initial debridement is in doubt, wound closure should be delayed until the surgeon is confident that no deep contaminants persist and there is no sign of active wound infection. In patients with severe contamination, or open fractures, antibiotics can be used to help control the onset of infection but should never be used as a substitute for surgical debridement. If needed, serial debridements should be performed at 48- to 72-hour intervals until the surgeon is satisfied that all contaminated and necrotic or nonviable tissues have been removed. Often in the case of open fractures or other high-energy injuries it is not possible to determine the full extent of soft tissue injury at the index debridement. Once adequate debridement has taken place, delayed primary closure can be attempted.
Not all wounds are amendable to primary closure, even on a delayed basis. Advancements in wound care technology have afforded new ways to achieve closure of a wound, decrease the need for flap coverage, and improve survival of split-thickness skin grafts. The most significant advancement is that of “vacuum-assisted wound closure,” or the wound VAC. The wound VAC is a closed, negative-pressure system for healing wounds. After a wound has been adequately debrided a reticulated polyurethane sponge is trimmed to fit the wound so that it is in direct contact with all wound surfaces and either packed into or placed on top of the wound. This is then covered with a clear adherent flexible plastic dressing through which passes a plastic tube that attaches to a suction/reservoir device. The VAC is typically changed roughly every 48 hours either at bedside or in the operating room if sedation is required. The pump is typically run at a continuous −125 mm Hg because this has shown to produce the peak improvement in blood flow without the pain from intermittent pressure with wound contraction/expansion.
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