Wounds, whether created electively or as a result of traumatic injury, are an integral component of the surgical patient thus understanding the pathways and mechanisms of wound healing is critical for the optimal care of surgical patients. This fund of knowledge is applicable to the care of patients with acute wounds as well as facilitates the development of therapeutic options for patients with chronic or nonhealing wounds. Wound healing is often divided into phases in order to aid understanding of this complex process and these are the early inflammatory phase, the intermediate proliferative phase, and the late maturational and remodeling phase. Although these phases are often described as discrete events, it is important to realize that characteristics and elements of these phases overlap. Wound repair is a dynamic and complex process of inflammation characterized by a well-coordinated pattern of cell migration, proliferation and differentiation, along with angiogenesis and matrix remodeling. The essential characteristics of the early phase include hemostasis and inflammation. The intermediate phase is characterized by cell proliferation, migration, angiogenesis, and epithelialization while the late phase involves collagen production with contraction of the wound. Ultimately, even in normal wounds, the wound undergoes continuous remodeling for the rest of the patient’s life (Table 47-1).
TABLE 47-1Phases of Wound Healing and Predominant Cells Involved at Each Stage ||Download (.pdf) TABLE 47-1 Phases of Wound Healing and Predominant Cells Involved at Each Stage
|Phase ||Cells involved ||Main activity during phase ||Time course |
|Hemostasis ||Platelets || |
Formation of platelet plug
Encourage cell adhesions
|Immediately following wounding |
|Inflammatory ||Neutrophils || |
Scavenging necrotic tissue
|6–48 h |
| ||Macrophages || |
|48–4 d |
Matrix synthesis; Collagen synthesis
48 h–14 d
3 days–3 mon
|Maturational || |
Collagen synthesis and remodeling
30 d–1 yr
21 d–1 yr
Wounds can heal by either regeneration or by repair but the vast majority of wounds in humans heal by repair. “Regeneration,” a process that involves replacement of damaged tissue with an exact replica which is indistinguishable from the original both morphologically as well as functionally, does not occur in mammalian skin. Rather, a process of “repair” occurs wherein a physiologic adaption of the injured tissue occurs to reestablish coverage or continuity that does not attempt to offer an exact replacement of the damaged skin. Thus, all mammalian wounds heal by scarring or repair and not by regeneration.
The process of wound healing starts with the inflammatory phase which commences as soon as the wound is created. Critical to this early phase, the wound must undergo hemostasis of disrupted blood vessels, clearing of any bacterial invaders and removal of devitalized tissue. Injury to tissue initiates a wide array of responses that alter the cellular ...