The infected wound

Wounds that have been managed by primary (or delayed primary) closure as well as wounds that have been left to heal by second intention can get infected and often require veterinary attention. Understanding the basics of wound healing and knowing underlying problems and factors that predispose to wound infection are essential in helping prevent, recognize, and adequately address wound infection in equids.

Excessive swelling, pain on palpation or associated with movement (lameness), wound discharge, and sometimes systemic signs of infection like fever, are indications of wound infection. Wounds managed by primary closure may get infected because of pre- or intraoperative bacterial contamination, and/or because factors like inadequate vascular supply (including bone sequestration), inadequate drainage, or excessive tension on the primarily adapted wound margins could not be eliminated or were simply not recognized and addressed as such. Infected primarily closed wounds are treated by removing suture material to provide passive drainage, additional incisions and lavage with dilute antiseptic solutions if needed, and if needed (depending on the nature and anatomic localization of the wound) systemic antimicrobial therapy based on antimicrobial sensitivity testing. Examples include incisional infection after primarily closed orthopedic lacerations and injuries with or without implants, or abdominal incisions after colic surgery.

Infected wounds left to heal by second intention, may present as slowly healing wounds with a prolonged inflammatory or proliferative phase with excessive discharge, or with a distinct lack of granulation tissue, or dark red and disrupted surfaces of granulation tissue, or with the formation of proud flesh. Gross contamination with bacteria or foreign material, particularly of deeper wound cavities and wounds with substantial disruption of the underlying blood supply, the presence of necrotic tissue (including bone sequestration), and excessive movement (particularly on wounds of the distal extremities) are causes of wound infection and wound healing disorders. In first aid situations, meticulous wound debridement and ensuring unrestricted drainage are important measures to help prevent wound infection for deep, contaminated wounds that are left open to heal by second intention. Thus, wounds healing by second intention may get infected days and even weeks after the initial insult, because they lack an epidermal and dermal tissue barrier to prevent bacterial colonization of deeper tissue layers until these are protected by a healthy bed of granulation tissue. Examples include degloving injuries or comminuted, open fractures of proximal splint bones. Moreover, traumatic extremity wounds may be predisposed to wound infection because the formation of protective granulation tissue can be delayed by the constant movement of exposed ligaments or tendons. These factors need to be recognized and considered when presented with such wounds in acute or chronic stages. Different possibilities and equipment for surgical and biological debridement of necrotic tissues, and bandaging techniques to optimize the wound environment with the correct choice of wound dressings, splints or casts for effective immobilization will be presented and discussed.