Postgrad Med J 1999;75:645–649 © The Fellowship of Postgraduate Medicine, 1999 Postgrad Med J: first published as 10.1136/pgmj.75.889.645 on 1 November 1999. Downloaded from Classic diseases revisited Necrotizing soft tissue infections John D Urschel Summary Necrotizing soft tissue infections are a highly lethal group of infections that Necrotizing soft tissue infections require early and aggressive surgical debridement.1–3 These infections may occur are a group of highly lethal infec- in almost any anatomic area, but they most frequently involve the abdomen, tions that typically occur after perineum, and lower extremities. Surgery and trauma are common aetiologies, trauma or surgery. Many indi- but in some cases the aetiology remains uncertain.45 Immunocompromised vidual infectious entities have patients, especially those with diabetes, are more likely to develop necrotizing been described, but they all have infections. A great deal of attention has been directed toward classifying these similar pathophysiologies, clinical infections by bacteriological features or layers of tissue involved, but it is useful features, and treatment ap- to view necrotizing infections as a spectrum of clinical conditions with similar proaches. The essentials of suc- pathophysiological features and common treatment principles.367In this review, cessful treatment include early the common treatment concepts applicable to all necrotizing soft tissue diagnosis, aggressive surgical de- infections will be emphasized, and the more important specific disease entities bridement, antibiotics, and sup- will be described. portive intensive treatment unit Clinical features of necrotizing soft tissue infections include wound pain, care. The two commonest pitfalls crepitus, foul watery wound discharge, skin blistering, and rapid progression to in management are failure of 18 early diagnosis and inadequate septic shock. The external appearance of the skin wound may initially betray surgical debridement. These life- the seriousness of the necrotizing infection beneath it (figure 1); this contributes to diagnostic delay. Soft tissue gas, detected clinically or radiologically, is a clas- threatening infections are often 9 mistaken for cellulitis or innocent sic sign, but its absence does not exclude the presence of a necrotizing infection. wound infections, and this is re- This common misconception is also responsible for delayed diagnosis in some sponsible for diagnostic delay. cases. The infection spreads rapidly through the soft tissue planes, and produces Tissue gas is not a universal severe systemic sepsis. Progression to septic shock, multiple organ failure, and finding in necrotizing soft tissue death ensues if aggressive treatment is not instituted immediately. Even with infections. This misconception timely and skilled treatment, death from necrotizing soft tissue infections is all also contributes to diagnostic er- too frequent.129 rors. Incision and drainage is an Some necrotizing infections are caused by single organisms. Myonecrosis (gas inappropriate surgical strategy gangrene) from Clostridium infection and necrotizing fasciitis from group A for necrotizing soft tissue infec- Streptococcus are two classic examples of monomicrobial necrotizing infection. tions; excisional debridement is However, most necrotizing soft tissue infections are caused by a mixture of aero- http://pmj.bmj.com/ needed. Hyperbaric oxygen bic and anaerobic bacteria, that act synergistically to cause fulminant therapy may be useful, but it is not infection.10 11 Organisms commonly identified include aerobic and anaerobic as important as aggressive surgi- streptococci, coagulase-negative and coagulase-positive staphylococci, faculta- cal therapy. Despite advances in tive and aerobic Gram-negative rods, Bacteroides species, and Clostridium antibiotic therapy and intensive species.910Facultative organisms lower the oxidation–reduction potential of the treatment unit medicine, the mor- wound microenvironment, and promote favourable conditions for the growth of tality of necrotizing soft tissue anaerobes. Anaerobes interfere with host phagocyte function, and thereby facili- on September 25, 2021 by guest. Protected copyright. infections is still high. This article tate the proliferation of aerobic bacteria.12 Several bacteria, such as Bacteroides emphasizes common treatment fragilis, produce â-lactamase enzymes that interfere with antibiotic activity. principles for all of these infec- Bacterial necrotoxins, such as those produced by Clostridium perfringens and tions, and reviews some of the Streptococcus pyogenes, cause tissue necrosis.1 In addition, the infectious process more important individual necro- activates the coagulation system that in turn produces local vascular thrombosis tizing soft tissue infectious enti- ties. and infarction. Bacterial heparinase production contributes to this process. As the infection progresses, pressure increases within the soft tissues causing further 11 Keywords: fasciitis; gas gangrene; clostrid- impairment of blood supply. ium infections; streptococcal infections; The diagnosis of necrotizing soft tissue infections is usually made at the time necrosis; debridement; surgical infections; of surgical exploration. Securing a diagnosis non-invasively is very diYcult; this soft tissue infections contributes to diagnostic delay, and the ultimate demise of many patients.213The clinical presentation is often mistaken for simple cellulitis. However, pain in the aVected region and systemic toxicity are more pronounced than would be expected in simple cellulitis.14 Despite recommendations for the diagnostic use Department of Surgery, McMaster of computed tomography and magnetic resonance imaging studies in these University, Hamilton, Ontario, Canada 15 16 J D Urschel infections, the best diagnostic strategy is to perform surgical exploration when clinical features raise the possibility of necrotizing soft tissue infection.17–19 Correspondence to John Urschel, MD, Chief of Initially, diagnostic surgical exploration can be very limited in scope; small inci- Surgery, St Joseph’s Hospital, 50 Charlton Avenue sions under local anaesthesia serve to establish the presence or absence of fascial East, Hamilton, Ontario, Canada L8N 4A6 and muscle necrosis. Frozen section examination of tissue specimens will estab- Accepted 3 June 1999 lish the diagnosis if the gross findings at surgical exploration leave any doubt 646 Urschel Postgrad Med J: first published as 10.1136/pgmj.75.889.645 on 1 November 1999. Downloaded from (figure 2).18 19 Although limited surgical interventions are appropriate for diagnostic purposes, there is no role for conservative surgical treatment strategies.3 Treatment of necrotizing soft tissue infections entails early surgical debridement, fluid resuscitation, antibiotics, and general cardiorespiratory sup- portive care to maintain vital organ function (box).20 21 After diagnostic delay, the most common pitfall in treatment is inadequacy of surgical debridement. Deb- ridement should be early and aggressive; all necrotic tissue must be excised (fig- ure 3).17 22 ‘Incision and drainage’ approaches are not appropriate. These infec- tions are characterized by necrotic tissue and watery drainage, as opposed to the Figure 1 External appearances often viable tissue and pus that characterize localized bacterial abscesses. Repeat deb- betray the seriousness of underlying ridement, sometimes on a daily basis, should be done until the local infectious infection. This woman was in septic shock at process has been arrested.23 24 After sepsis is controlled, coverage of the wound is the time this photograph was taken. Despite amputation, fulminant sepsis led to death usually obtained by skin grafting. within 24 hours of amputation Intravenous fluid resuscitation, mechanical ventilation, and inotropic support are instituted according to established principles for managing septic shock. These principles are reviewed elsewhere.25–27 Nutritional support is started after urgent resuscitation and debridement are carried out. Antibiotic coverage should be broad-spectrum, and anaerobic coverage is essential. Many antibiotic combi- nations are acceptable. Usually penicillin (or a cephalosporin), anaerobic cover- age (clindamycin or metronidazole), and Gram-negative coverage (aminoglyco- side, third-generation cephalosporin, or ciprofloxacin) are used together.1 Antimicrobial therapy of life-threatening surgical infections has recently been reviewed in detail elsewhere.11 28 29 Antibiotics are modified after Gram stains and culture reports become available. Blood cultures and wound cultures are both useful, but simple wound swabs are often inadequate for proper culturing. Wound tissue samples should be sent in both aerobic and anaerobic containers. Figure 2 Histology shows necrotic Finally, antibiotic treatment is also guided by the information gained during connective tissue and acute inflammatory surgical exploration. Operative findings may be indicative of one of several dis- cells (haematoxylin and eosin, × 200). The tinct clinical–bacteriologic infectious entities (reviewed below). patient suVered from polymicrobial Hyperbaric oxygen therapy has an uncertain role in the management of necrotizing fasciitis involving the abdominal 21 30 31 wall necrotizing soft tissue infections. Some studies suggest a survival benefit, but others do not.24 32 Survival from clostridial myonecrosis is probably improved by hyperbaric oxygen therapy.32 33 For other types of necrotizing soft