Necrotizing Soft Tissue Infections : Wheeless' Textbook of Orthopaedics

- Discussion:
- necrotizing fascitits is any necrotizing soft tissue infection spreading along fascial planes, with or without overlying cellulitis;
    - rapidly progressive inflammation and necrosis of subQ tissues and deep layer of superficial fascia with sparing of deep fascia and muscle;
    - also called Meleney ulcer, NF is severe manifestation of lymphangitis that progresses in a frightening manner within a few hours;
- tissue necrosis develops rapidly behind advancing wall of inflammation that limits penetration by antibiotics;
- desquamation followed by gangrene may be relentless;
    - clinical findings:
           - clinical signs of pain out of proportion to exam coupled with areas of anesthesia (from microvascular and nerve damage)
           - hyperyrexia, and chills are severe;
       - skin lesions are incised and drained or aspirated to obtain fluid for culture;
       - initial findings are localized pain and minimal swelling, often w/ no visible trauma or discoloration of the skin;
       - dermal induration and erythema eventually become evident;
           - firm, tense, "woody" induration of the subcutaneous tissues;
           - eventually the patient has limited range of motion, chills, fever;
           - probe open wounds:
                    - dx is confirmed when a probed can be passed laterally along fascial cleft in a open wound;
                    - probing edges with a blunt instrument permits ready dissection of the superficial fascia well beyond the wound margins;
           - blistering of the epidermis is a late finding;
           - hyponatremia and hyperkalemia are ominous findings;
                    - ref: Necrotizing fasciitis of the extremities: a prospective study
    - historical note:
           - necrotising fasciitis was originally named by Wilson in 1952: Wilson B. Necrotizing fasciitis. Am Surg 1952; 18:416.
           - other previous descriptions include: haemolytic gangrene, acute streptococcal gangrene, gangrenous erysipelas, necrotising
                     erysipelas, suppurative fasciitis, and hospital gangrene
             - ref: Paediatric Surgery: A Comprehensive Text For Africa [Chapter 21]

Organisms:
    - gram stain:
            - Gram Negative Bacilli: / Gram Negative Cocci: / Gram Positive Bacilli: Gram Positive Bacilli
          - bacterial Menu:
    - may be caused by single organism - streptococci pyogenes or vibrio, or may be caused by a combination of organisms;
- anaerobic or microaerophilic streptococci are believed to be the usual cause, but these microorganisms are difficult to culture;
- clostridium perfringes :
            - ref: Gas Gangrene of a Prosthetic Hip
    - staph aureus / MRSA
          - ref: Necrotizing fasciitis caused by methicillin-resistant Staphylococcus aureus resulting in death. A report of three cases.
    - vibrio (vulnificus):
      - typically the patient is exposed to sea water
      - course is measured in hours esp in alcoholics and diabetics;
      - despite in vitro sensitivity to tetracycline, response to ATB is poor;
      - immediate wide excision and amputation may be necessary;
          - references:
                - Necrotizing Soft-tissue Infections and Sepsis Caused by Vibrio vulnificus Compared with Those Caused by Aeromonas Species.
                    - Infections caused by halophilic marine Vibrio bacteria.
    - streptococci pyogenes infections:
           - isolation of group A Streptococcus from a normally sterile body site or 4-fold rise against: streptolysin O, DNase B
         - most superficial form is impetigo which affects stratum corneum;
- ecthyma contagiosum describes shallow superficial dermal ulcers caused by a slightly deeper infectios;
- erysipelas is the term for streptococcal dermal cellulitis, often associated with lymphangitis as it spreads along dermal lymphatics;
- cellulitis can spread to the dermal lymphatics as classical lymphangitis, commonly causeced by strep pyogenes;
- necrotizing streptococal infections:
- acute gangrene: at level of fascia, streptococci pyogenes, produces acute gangrene, a form of necrotizing fascitis;
- initially there is rapid onset of marked tissue edema and redness w/ little pain, progressing to local cyanosis & skin blistering;
                   - lymphangitis and lymphadenopathy are absent;
- soft tissue gas may be uncommon;
                   - serious systemic disease
                          - shock (systolic blood pressure <90 mm of Hg)
                          - DIC
                          - respiratory failure, liver failure, renal failure
                   - treatment is parental penicillin, debridement, and measures to prevent edema;
- before antibiotics were available this was a surgical emergency mandating immediate amputation to
                          prevent streptococcal septicemia and death;
                   - w/ a high suspicion that a group-A streptococcus was the pathogen, intravenous immune globulin therapy should beinitiated;
                   - ref: Necrotizing fasciitis with toxic shock syndrome in a child: a case report and review of literature

- Treatment:
     - Antibiotic Menu
             - IV infusion of aqueous penicillin must be instituted immediately;
             - typically ATB is given without response, unless concomitant radical debridement is also performed;
     - Radical Surgical Debridement:
             - fascial planes are extensively opened and debrided;
             - every anecdotal story about necrotizing fascitis seems to involve the retrospective wish on the part of the surgeon that a
                      much more radical debridement
                     had be performed;
             - fasciotomy / fasciectomy
                     - single or multiple linear incisions over the affected areas;
             - muscle debridement:
                     - muscle necrosis occurs in patients with strep infections (gangrenous streptococcal myositis) which is similar to
                                 clostridial myonecrosis (gas gangrene) but there is no gas in the tissues;
             - ref: Aggressive surgical management of necrotizing fasciitis serves to decrease mortality: a retrospective study.