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Death after traumatic injury has been described in terms of a trimodal distribution. Immediate and acute (<24 hours) deaths usually result from uncontrolled hemorrhage, but infections and multiple organ dysfunction syndrome, which often arise from infection, are responsible for a significant proportion of late deaths. Indeed, infection is responsible for most deaths in patients who survive longer than 48 hours after trauma.1 Trauma-related infections are generally divided into those that result directly from the injury (e.g., due to contamination that occurs in conjunction with the traumatic injury) and nosocomial infections that arise in the health care setting, secondary to treatment of the injury. The pathogens involved can be exogenous or endogenous bacteria, depending on the mechanism of injury and/or the iatrogenic cause. Most post-traumatic infections are polymicrobial and involve a mixture of aerobic and anaerobic organisms.2 In one series, 37–45% of all trauma patients experienced infectious complications during their initial hospitalization. Furthermore, in the same study, 80% of trauma patients staying at least 7 days in the intensive care unit met systemic inflammatory response syndrome (SIRS) criteria.3 Therefore, it is important that all caregivers understand the principles of surgical infections in the context of trauma patients. This chapter discusses the following: factors that normally prevent infection, how trauma disrupts or overwhelms normal host defenses, how to recognize and treat the most common infectious complications after traumatic injury, principles that can be employed to prevent infection, and how those principles can be applied chronologically during the treatment of trauma patients.

Humans have evolved mechanisms to avoid infection despite the ubiquitous presence of bacteria in our environment and throughout our bodies. Under normal circumstances there is a balance between bacteria, intact environmental barriers, and host defenses (see Fig. 18-1). With surgery in general, and trauma in particular, there is a disruption in this balance that significantly increases the probability of developing an infection (Fig. 18-2). Bacteria are abundant on the surface of the skin, within the oral cavity, and present in increasing numbers down the length of the gastrointestinal tract. Bacterial numbers differ at various locations, and the pathogenic species and their respective numbers at different anatomic sites are summarized in Table 18-1. Trauma disrupts the environmental barriers that prevent bacteria from gaining access to normally sterile regions of the body. When inoculation of bacteria into normally sterile sites occurs, infection will ensue if bacteria can proliferate faster than the host defense mechanisms can eradicate them. Furthermore, there is potential for much greater disruption of normal barriers with trauma than occurs with elective surgery as there is often concomitant hypoperfusion (shock), devitalized tissue, and retained foreign bodies.

Table 18-1 Pathogenic Microorganisms Present at Various Anatomic Sites

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