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An acute wound can be defined as an unplanned disruption in the integrity of the skin, including the epidermis and dermis. The goals of wound management are to restore tissue continuity and function, minimize infection, repair with minimal cosmetic deformity, and be able to distinguish wounds that require special care. The principles of wound management should be emphasized over the repair technique. Appropriate wound management prior to approximating the wound will allow it to heal with minimal complications. This includes wound cleansing, debridement of the wound edges, wound approximation, and prevention of secondary injury.
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Phases of Wound Healing
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The response of tissue to an injury is described in three phases. The first phase is coagulation and inflammation. The second phase is the proliferative phase. The final phase is the reepithelialization or remodeling phase.
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Phase I consists of coagulation and inflammation. It occurs in the first 5 days. This phase is also known as the vascular phase. A fibrin clot forms a transitional matrix that allows for the migration of cells into the wound site over a period of 72 hours. Inflammatory cells (i.e., neutrophils, monocytes, and macrophages) kill microbes, prevent microbial colonization, break down soluble wound debris, and secrete cytokines. The cytokines signal synthetic cells, such as fibroblasts, to initiate phase II. Most sutured wounds develop an epithelial covering that is impermeable to water within 24 to 28 hours.
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Phase II is the proliferative phase. It occurs during days 5 to 14 after the injury. Fibroblasts proliferate and synthesize a new connective tissue matrix that replaces the transitional fibrin matrix. Granulation tissue consisting of fibroblasts, immature connective tissue, epidermal cells that have migrated, and abundant capillaries forms within the wound. Fibroblasts release collagen, a protein substance that is the chief constituent of connective tissue. At 5 days, the tensile strength of the wound itself is 5% that of normal skin. Collagen formation peaks at day 7.
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Phase III is known as the remodeling, reepithelialization, or maturation phase. It occurs from day 14 and lasts until there is complete healing of the wound. The new granulation tissue is being converted into a scar. The scar consists of a rich matrix with decreasing cell density, decreasing vascular density, and increasing thickness of collagen fiber bundles packed in parallel arrays.1 The wound will have 15% to 20% of its full strength at 3 weeks and 60% of its full strength at 4 months. Tensile strength continues to increase up to 1 year after wounding. The skin will eventually regain only 70% to 90% of its original tensile strength.
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Factors Affecting Normal Repair
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The most common causes of improper wound healing are tension on the wound edges, necrosis and/or ischemia of the tissues from local conditions (e.g., crush injuries and contusions decrease blood flow and lymphatic drainage, which alters local defense mechanisms), or shock. Hypovolemia is the ...