Abstract and Introduction
Accidents or violence can result in penetrating trauma in the adult population. Contaminated penetrating foreign bodies introduced at the time of wounding cause infection, especially high velocity projectiles, which result in cavitation. Surgical debridement reduces potential infection; however, perioperative antibiotics are usually indicated owing to studies demonstrating high rates of sepsis in the pre-antibiotic era. Trauma-associated pathogens include Gram-positive, Gram-negative and anaerobic pathogens. Antibiotic resistance is increasing, and several recent panels have sought to develop guidelines for perioperative prevention and empiric treatment of infection to limit usage and reduce selective pressure for resistance. We review infections of the CNS, thorax, abdomen and extremities following penetrating trauma injury, as well as the data supporting a reasonable antimicrobial approach.
Infection associated with penetrating trauma is generally a sequela of accidents or violence. As this subject has a broad scope, we have limited discussion to infections from traumatic injuries in adults. Penetrating traumas differ from blunt traumas, such as motor vehicle accidents, in that the skin is penetrated by the traumatic injury such as sharp objects and missiles. A critical aspect of penetrating trauma is the formula of kinetic energy, energy (E) = ½MV2 , where M is mass and V velocity. Thus velocity of the penetrating object is a more important component of the injury than object size. Injuries can be divided into very low energy (VLE) such as knife or stab wounds, low energy (LE) such as handguns, and high energy (HE) such as military rifles.
A review of the infection epidemiology in VLE injury is unrevealing. A large study of almost 40,000 knife wounds from Canadian emergency rooms failed to describe infection rates. A recent review of 70 arrow injuries reported a 1.4% infection rate. Stab wounds to the spine 'rarely become infected'.[4,5] Knife wounds of the abdomen are perhaps the exception; a recent paper where knife wounds comprised 19% of abdominal injuries described a 50% infection rate. Knife injuries have comprised two trials of antibiotic prophylaxis for intra-abdominal infection (IAI)[7,8] but these are not designed to describe epidemiology. Otherwise, we found no further epidemiologic descriptions. Clearly, a well-designed trial to describe infection rates and pathogens encountered in VLE injuries is needed. The paucity of literature suggests that infections in these types of injuries are perhaps unlikely, with the exception of blunt objects with irregular tips such as screwdrivers, which can introduce foreign material. This is intuitive because the LE of the injury does not cause cavitation, allowing for all wound surfaces to re-approximate, creating a greater surface area in contact with the immune system, and preventing pathogen and foreign debris spread into surrounding tissue.
Penetrating missiles can be further differentiated into those from bullets, and those from fragmentation weapons such as grenades, antipersonnel mines or, as in recent asymmetrical warfare conflicts, the 'improvised explosive device' (IED). IEDs are homemade using a variety of materials intended to penetrate, blast and burn with unique and unpredictable injury patterns. This differentiation is important as the resulting wound from each weapon is unique. Bullets have an available kinetic energy of 1500–3000 joules (J) for military rifles, 300–500 J for handguns and 10–150 J for some fragmentation devices. This energy lacerates, contuses and displaces body tissues. In LE wounds, injury is confined to the track of the projectile where the tissue is crushed by the bullet or fragment. HE wounds produce a radial injury around the track of the projectile with a temporary cavity where contaminants can be widely dispersed. Fragmentation device impact velocities with high explosives such as IEDs vary by fragment size and proximity to the device detonation, but range from 100–1000 m/s. This results primarily in soft-tissue injury, sometimes with adjacent bony involvement. Furthermore, fragmentation devices create multiple wounds that are irregularly shaped and heavily contaminated with foreign bodies such as soil and clothing, with subsequent infection highly likely. Most bullets are pointed and thereby initially transfer little material at entry. However, if cavitation occurs, bullet material may be sucked into the exit site as the cavity collapses back down and become widely dispersed, increasing infection risk.
Bullets, despite being the product of an explosion that creates heat, were shown to be nonsterile in the 1960s. Contamination notwithstanding, over 50% of bullet fragments are left unextracted without developing secondary infection, probably because metallic foreign bodies do not readily serve as a nidus of infection and have a low inflammatory potential. Nonmetallic foreign bodies appear to be a greater cause of infection. War wounds have the highest infection potential, owing to their HE projectiles, a contaminated wounding environment and delay to definitive surgery compared with LE civilian injuries. A study of 17,726 combat wound casualties during the Vietnam war showed an infection incidence of 3.9% in the first 2 weeks after injury. In reality, the incidence was probably higher because data was collected at an in-theater hospital; many patients lost to follow-up after 15 days might have gone on to suffer late infection.
Although primarily young and without comorbidities, the penetrating trauma patient is often a diagnostic conundrum, and nowhere is this more apparent than in HE injuries. Owing to massive hemorrhage, tissues are ischemic with impaired leukocyte and antimicrobial delivery to affected tissues. Furthermore, multiple transfusions are required, in effect causing a complete exchange transfusion, removing the victims' circulating immunity. There may be accompanying traumatic brain injury, impairing autonomic regulatory mechanisms. Recent studies indicate that severe blast injury (so prevalent in the current conflict) overwhelms the immune system, thus sustained hyperinflammation ensues, which the host cannot physiologically regulate. This dysregulation can lead to systemic inflammatory response syndrome (fever, hypotension and leukocytosis, among others) that may mimic infection, making diagnosis difficult and leading to inappropriate antibiotic administration. Conversely, these factors can also increase infection susceptibility at the penetrating injury site requiring antibiotic treatment. Thus, the decision of when to administer antibiotics and what agent to select is an important and challenging one in penetrating trauma injury.
Expert Rev Anti Infect Ther. 2011;9(1):81-96. © 2011 Expert Reviews Ltd.
Cite this: Prophylaxis and Treatment of Infections Associated with Penetrating Traumatic Injury - Medscape - Jan 01, 2011.