Soft Tissue Debridement Definition

Definition and OverviewThe majority of infections affecting the skin and soft tissues are superficial, requiring only antibiotic therapy. However, more serious infections, particularly cellulitis, occasionally require drainage as part of the management.On rare occasions, pathogens enter the subcutaneous tissues and spread through deeper layers, such as the fascia and the muscles, causing tissue ischemia, necrosis, and death. Deep, necrotising infections have been referred to using various terminologies, depending on the layer of soft tissue involved and the specific pathogen responsible for them. These terms include gas gangrene, necrotising fasciitis, and Fournier gangrene, to name a few. In general, these conditions are known as necrotising soft tissue infections, or NSTI.These kinds of infections are usually aggressive, necessitating a combination of urgent surgical intervention and strong antimicrobial therapy.

Who Should Undergo and Expected ResultsNecrotising soft tissue infections encompass a spectrum of disease conditions characterised by rapidly progressive inflammation of the soft tissues, typically involving the muscles and the fascia.Immunocompromised individuals are at highest risk for NSTIs. Elderly individuals and patients with co-morbid conditions, such as malnutrition, mellitus, cancer, and peripheral vascular disease, are commonly affected.The clinical manifestations of NSTI vary widely, ranging from minimal erythema with extensive underlying tissue involvement to an early septic course with gross necrosis of the skin. The physician should be wary when clinical signs, such as crepitus, eruption of small vesicles on the skin, induration, and oedema outside the area of redness, occur as these suggest the involvement of deeper layers.

The extremities, the perineum, and the torso are the commonly affected areas. Signs of advanced disease include, gangrene, and systemic shock.Establishing a diagnosis early in the course of the disease is crucial to begin timely and appropriate treatment to avoid life-threatening complications.

Although gram-positive bacteria are commonly encountered, the majority of NSTIs are caused by multiple organisms (polymicrobial); hence the need for powerful antibiotics. Broad-spectrum antibiotics are started empirically, and shifted to targeted anti-bacterial drugs once culture results are available. Surgical intervention, specifically debridement, is likewise performed without delay.Despite significant developments in medicine and intensive care, necrotising infections remain associated with high mortality rates (16-25%).

Debridement Surgery Recovery

If not managed adequately, mortality rates can go as high as 80-100%. NSTI cases should be managed by a multi-disciplinary team of health care practitioners to ensure appropriate and specialised care for these patients. How is the Procedure Performed?Source control is a vital component in the management of necrotising infections. The principle of source control is facilitated by surgical intervention, specifically debridement. Debridement is a surgical procedure that involves the removal of all necrotic tissues, including the skin, subcutaneous tissues, muscles, and fascia. For necrotising soft tissue infections, debridement is best conducted under general anaesthesia.Since NSTIs are progressive, debridement should be performed as soon as the condition is diagnosed.

A liberal incision is done to remove as much dead tissue as possible. The debridement is continued until healthy, raw tissues with good blood supply are encountered. In certain instances, the procedure may necessitate extensive excision of tissues leading to disfigurement or amputation.

However, complete debridement must be performed because an incomplete operation remains associated with higher mortality and morbidity rates.If possible, primary closure is performed after debridement. However, radical excision may result in massive defects requiring reconstruction, which may be delayed or performed during the same operation, depending on the extent of the defect and the patient’s status. Flaps and skin grafts may have to be performed to ensure adequate coverage of healthy underlying tissues.

On occasion, especially for dirty wounds and in cases where a repeat debridement is expected, the wound may be left open and covered with saline- or Daikin’s solution-soaked dressing. A “second look” procedure may be necessary to check if the debridement is adequate and if there is disease progression.Specimens acquired during the procedure are sent for culture studies to facilitate directed antibiotic therapy postoperatively. Possible Risks and ComplicationsAfter the operation, rigorous monitoring in the intensive care unit is paramount. A substantial systemic inflammatory response is expected postoperatively in patients with necrotising infections, which may lead to the development of organ failure such as respiratory distress, kidney injury, septic shock, and even death. Aggressive management and continued physiologic support, including fluid resuscitation, adequate nutrition, and even mechanical ventilation, are thus crucial.

Comprehensive antibiotic coverage cannot be overemphasised. Early patient mobilisation is likewise recommended. New studies are focusing on the possible benefits of using hyperbaric oxygen and intravenous immunoglobulins for these cases.Debridement for necrotising soft tissue infections typically results in large and complex wounds, which may lead to a number of complications. Exposure of important structures, such as cartilage and bone, to the external environment should be avoided to prevent these structures from drying out. Repeated irrigation and lavage of open wounds facilitate the removal of debris and bacteria. A negative pressure or vacuum-assisted device may be applied to the wound to improve vascularisation and healing. Adequate wound coverage minimises fluid and electrolyte loss, and protection from infection and desiccation.

Various options, including xenografts and skin substitutes, may be employed. For large abdominal defects, synthetic materials, such as biologic implants or absorbable mesh, may serve as a bridge prior to definitive closure of the wound. The development of subsequent wound complications, such as a ventral, can be managed at a later time.Pain management after debridement, particularly during dressing changes, should be optimised. The use of appropriate pharmacologic therapies, such as narcotics, should be instituted to achieve pain relief. Neuropathic pain, such as that following amputation, may be managed with medications like gabapentin.

Adequate pain control also promotes movement, which can help prevent complications, such as contractures.Extensive debridement can result in significant loss of function for the patient. Rehabilitation should be done in order to ensure return of function, achieve independence, and optimise the patient’s quality of life.References:.Stevens DL, Bisno AL, Chambers HF, Everett ED, Dellinger P, Goldstein EJ.

Practice guidelines for the diagnosis and management of skin and soft-tissue infections. Clin Infect Dis.

41(10):1373-406.Guideline Stevens DL, Bisno AL, Chambers HF, et al. Practice guidelines for the diagnosis and management of skin and soft tissue infections: 2014 update by the infectious diseases society of america. Clin Infect Dis.

Printout: Necrotizing Soft Tissue Infections-Definition/CausesNecrotizing Soft Tissue Infections - Definition and CausesNecrotizing soft tissue infections are infrequent but highly lethal infections. It is estimated that there arebetween 500-1,500 new cases of necrotizing soft tissue infections per year in the US and a recentepidemiologic population-based study estimated the incidence of necrotizing softtissue infections to beapproximately 0.04/1,000 person-years with information derived from an insuranceadministrative database from various states in the United States.

It isunclear if the incidence of this disease is increasing. However, its aggressivecourse, poor prognosis, and media-mediated awareness have certainly raisedinterest in the medical and general community.

It is associated with devastatingconsequences including high mortality, disfigurement, disability, long-termrehabilitation and significant costs and resource utilization. Necrotizing softtissue infections occurfrequently enough that most primary care physicians, surgeons, and infectiousdisease specialists will see one or more during a professional career, but areinfrequent enough that few will have significant experience and confidence indealing with them.DEFINITION ANDNOMENCLATURESince the first description of necrotizing soft tissue infections by Jones, multiple terms have been used todefine different kinds of necrotizing infections of the soft tissues. The termsused have been based on anatomic location of infection, soft tissue compartmentinvolved, microbiologic and clinical features. Table 1 lists thedifferent terms used to refer to necrotizing soft tissue infections. These terms have been used in an attemptto define “different” entities or to classify necrotizing soft tissue infections according to the abovevariables. But the reality is that the use of all these different definitionsonly leads to confusion and lacks any clinical or academic purpose.Necrotizing soft tissue infections are defined by the presence of aspreading infection in any of the layers of the soft tissues (skin, subcutaneoustissue, superficial fascia, deep fascia, or muscles) which is associated withthe presence of necrosis of the layer/s involved and hence requires surgical debridement.

Allnecrotizing soft tissue infections fulfill this definition and have common features in theirclinical presentation and diagnosis, and most importantly, all of theseinfections by definition require surgical debridement. It is because of thisthat labeling or classifying them with different terms does not serve a usefulpurpose and may in fact complicate management by delaying diagnosis and/ordelaying surgical debridement. The true discriminative information that isessential for the management of soft tissue infections is the presence orabsence of a necrotizing component and this should be the focus during theinitial assessment of patients with soft tissue infections. As we will describein the coming sections, narrowing the type of necrotizing soft tissue infections to Group A β-hemolyticStreptococcus (GAS) or clostridial infection may be useful in better definingprognosis and in identifying patients that may benefit from additional treatmentoptions.

However, the general presentation, diagnosis, and management follow thesame principles and we encourage the use of the unifying term necrotizing softtissue infections whenreferring to all these entities.Table 1. Common Terms Used to Refer to SpecificTypes of Necrotizing Soft Tissue InfectionsDifferent nomenclature.Hospital gangrene.Hemolytic streptococcalgangrene.Phagedena.Meleney’s gangrene.Progressive bacterialsynergistic gangrene.Gas gangrene.Necrotizing cellulites.Necrotizing fasciitis.Necrotizing myositis.Myonecrosis.Clostridial myonecrosis.Clostridial cellulitis.Streptococcal myositis.Fournier’s gangreneRISK FACTORSAND ETIOLOGYRisk FactorsAlthough multiple risk factors for necrotizing soft tissue infections have been described, there are nostudies specifically addressing this issue. Risk factors listed in theliterature include: advanced age, diabetes mellitus, obesity, alcohol-use,intravenous drug use (IVDU), malnutrition, immune suppression, peripheralvascular disease, steroid use, and NSAIDs among others. Theseshould be interpreted as conditions that have been associated with necrotizingsoft tissue infections but lackdata to support them as predictive of necrotizing soft tissue infections occurrence. Furthermore reports fromdifferent studies could be representing different population of patients withunequal characteristics. For example, in the study published by Wall et al, inwhich 31 patients with necrotizing soft tissue infections were compared to 328 patients with non-necrotizingsoft tissue infections, no specific conditions were found to be predictive ofnecrotizing soft tissue infections, except for intravenous drug use as an etiologic factor (and possibly risk factor too).However this population of patients had a very high representation ofintravenous drug use (71%)as compared to other series.

On the other hand, a more recent study alsocomparing patients with necrotizing soft tissue infections (n=89) with those with non-necrotizing soft tissueinfections (n=225) showed that the former were more likely to have comorbiditiesand were more commonly associated with the presence of DM (70% vs. 51%, no pvalue provided). Although no other studies comparing necrotizing soft tissue infections withnon-necrotizing soft tissue infections have been identified, and establishingrisk factors for necrotizing soft tissue infections remains difficult, multiple large series have reportedwhat appeared to be meaningful associations between necrotizing soft tissueinfections and the presence ofchronic comorbidities, particularly the presence of diabetes mellitus andobesity (30-97% range). It remains unclear whether theseare true risk factors for necrotizing soft tissue infections, but it is prudent to have a high index ofsuspicion in patients with chronic and debilitating comorbidities (DM, obesity,immune suppression, etc) who present with clinical or laboratory findingssuggestive of necrotizing soft tissue infections.NSAIDs have previously been described as risk factors and even causative factorsfor necrotizing soft tissue infections. However subsequent studies have failed to find significant relationbetween the use of NSAIDs and necrotizing soft tissue infections. Their use can certainly mask the initialsymptoms from an ongoing soft tissue infection that can eventually progresstowards necrotizing soft tissue infections, but true necrotizing soft tissueinfections will probably progress regardless of the use ofNSAIDs and good clinical judgment will be the key to early diagnosis andtreatment.EtiologyThere are many events that can serve as etiologic factors to necrotizing softtissue infections.

Some of thepublished ones include: injection, trauma (lacerations, abrasions, wounds,etc.), insect bites, chronic wounds/ulcers, postoperative infections, perirectalabscesses, progression of minor soft tissue infections (furuncles, abscesses),etc. Two main points deserve emphasis regarding the etiology of necrotizing softtissue infections. First,idiopathic necrotizing soft tissue infections (those occurring in previously healthy patients without anobvious source) constitute up to 20% of causes in major series, making a highlevel of suspicion a key factor in diagnosing the disease in patients that maynot have a typical history leading to it. These patients have ahigher incidence of GAS related necrotizing soft tissue infections and infections more commonly compromise theextremities. Secondly, patients that are intravenous drug use are definitely at an increasedrisk of developing necrotizing soft tissue infections. Intravenous drug use is the route of entry and cause of infection in7-56% of recent series and has its own features worth mentioning. Intravenous Drug Use-Related Necrotizing Soft TissueInfection.Bosshardt, et al published a series of patients with predominantly intravenousdrug use-relatednecrotizing soft tissue infections over a 5-year period and showed that the incidence more than doubled whencompared to the first years of the study.

These infections seem to beparticularly associated with subcutaneous and muscle injection (skinpopping/muscling) of “black-tar heroin”, a cheaper, dark and gummy form ofheroin that is usually mixed with diluents like dirt or coffee allowing forbacterial spores to be introduced. Most of these infections are polymicrobialbut a high prevalence of anaerobic bacteria including clostridium species hasbeen reported, which explains the high white blood cell counts associated withit as well as its rapid progression and high mortality rate, in the order of45%. Intravenous drug use patients should be considered as a high-risk group for developing necrotizing soft tissue infectionsand when evaluated for soft tissue infections should undergo a thoroughassessment that can confidently rule out a necrotizing infection.

Admissions ofmultiple intravenous drug use patients with necrotizing soft tissue infectionsin a short interval should raise the concern for an outbreak from a “bad lot ofheroin” as has previously been described in the United Kingdom and inCalifornia.MICROBIOLOGYNecrotizing soft tissue infections are typically polymicrobial in nature. Some of the largest seriesevaluating the microbiology of necrotizing soft tissue infections showed that 84-85% ofnecrotizing soft tissue infections werepolymicrobial in nature. Of these, the most common microorganismsisolated vary according to patient population, however in most series the threemost common isolates are anaerobic bacteria (primarilybacteroides,Grampositive cocci and clostridium), staphylococcus and streptococcus species. Other less commonreported isolates include Enterobacteriaceae, fungal species and specificallyMucormycosis and Vibrio species, both of which usually occur in immunesuppressed hosts and carry an elevated mortality in the order of 40-80%. Table 5 lists the most common isolates from one of the largest series evaluatingmicrobiology patterns of necrotizing soft tissue infections.Table 5. Isolated Microorganisms and Type of Infections from Patientswith Necrotizing Soft TissueInfections in a Series of 182 Patients MICROORGANISMNo. Of isolates (n=791 isolates)Anaerobes263Bacteroides/Prevotella spp136Peptostreptococcus49Clostridium37Streptococcus species (includingenterococcus)236Groups A β-hemolytic57Staphylococcus species77Other (including other Gram positives,Gram negatives and fungi)215TYPE OF INFECTIONNumber of patients (n=182)Polymicrobial infection154 (85%)Monomicrobial infection28 (15%)Group Aβ-hemolytic streptococcus15 (54%)Clostridiumspecies4 (15%)Other9 (31%)Monomicrobial infections are less common presenting in approximately 14-15% ofcases from major series.

The most common isolates include Group A beta-hemolyticStreptococcal pyogenes (GAS), clostridialinfections and more recently staphylococcus species. Series with largerrepresentation of these isolates typically have a higher percentage ofmonomicrobial infections. Recent reports indicate that communityacquired methicillin Staphylococcus aureus (CA-MRSA) can cause necrotizingsoft tissue infections as a sole pathogen something that was extremely rare inthe past.Two specific infections are worth mentioning in more detail, those caused by GASand those caused by clostridial species. They share some similarities includingtheir unique ability to infect all the different compartments of the softtissues including subcutaneous tissue, the fascial layers and/or the musclecompartments (myonecrosis/myositis). Although they are usually part ofpolymicrobial isolates, both have been reported as the most common causes ofmonomicrobial infections.

They also cause a rapidly progressive, severe form ofnecrotizing soft tissue infections mediated through exotoxins in the case of clostridial infections andthrough cell wall components (M-protein) and exotoxins (streptococcal pyrogenicexotoxins –SPE A, B and C-) in GAS infections.