NECROTIZING SOFT TISSUE INFECTIONS

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NECROTIZING SOFT TISSUE INFECTIONS
Michael G. House, M.D. Sinai Hospital Case
Conference 20 June 2006
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• Terms applied to necrotizing soft tissue
  infections
• Necrotizing fasciitis
• Necrotizing cellulitis
• Fourniers gangrene
• Clostridial/Nonclostridial gas gangrene
• Hemolytic streptococcal gangrene

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Necrotizing fasciitis (NF) Def rapidly
progressive soft tissue infection characterized
by inflammation and necrosis confined to the
subcutaneous fascial tissues (with or without
necrosis of underlying muscle) Type I NF (90 of
cases) Polymicrobial infection with obligate
anaerobes (Clostridium sp), Gram- rods
(Klebsiella), non-group A Strep, Staph Type II
NF (10 of cases) Monomicrobial infection with
group A Strep (flesh-eating bacterium) Type
III NF (rare) Vibrio sp (marine)
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• 7500 cases in U.S. each year
• Overall mortality rate for NF 30
• Type II NF usually severely ill and have
  increased mortality
• STSS (Strep toxic shock syndrome) risk factor
  for death
• Risk factors for NF age gt 50y, male, DM, PVD,
  obesity, EtOH abuse
• Risk factors for Type II NF exposure to children
  w/ Strep throat, HIV, IVDA, steroid use,
  African-American, antecedent VZV
• Inciting events contaminated penetrating wounds,
  insect bites, IM/SQ injections, surgery, vaginal
  delivery, intramuscular hematoma w/wo skin break,
  skin contact w seawater or contaminated seafood

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• Pathological features necrosis of subcutaneous
  fat, nerves, and vessels (obliterative
  vasculitis)
• Superficial skin and deep muscle usually spared
• Fascial edema w dull gray appearance
• Lack of bleeding and tissue plane resistance
• Foul-smelling dirty dishwater discharge

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Stages of NF progression I (Early) Tenderness to
palpation (beyond area of cellulitis) Erythema/war
mth Edema II (Intermediate) Bullae
formation Skin fluctuance or induration III
(Late) Hemorrhagic bullae or skin
necrosis Crepitus Skin anesthesia
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The most effective treatment for necrotizing soft
tissue infections EARLY DIAGNOSIS Skin changes
are usually much less extensive then the
underlying infection Alerts high fever,
hypotension, tachycardia, MODS
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Diagnosis Suspicion Physical exam Plain
films CT MRI (leads to delay)
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Treatment Prompt debridement of all devitalized
tissue Surgical mortality 6 (lt24hrs), 24
(gt24hrs) Repeat debridements Antibiotics should
be broad-spectrum until cultures return Zosyn,
Timentin, Unasyn Vancomycin Type II NF PCN
Clindamycin Tetanus toxoid
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Clindamycin benefit or not? 3 retrospective
studies (Type II NF) Kaul 1997 77 pts No
effect on mortality Zimbelman 1999 56
pts mortality Mulla 2003 195 pts mortality 89
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• Hyperbaric Oxygen (HBO)
• Reduces local edema
• Increases angiogenesis and improves wound healing
• Kills obligate anaerobic bacteria
• Increases neutrophil phagocytosis
• Two retrospective studies suggest improved
  mortality and morbidity (Jallali et al, Am J Surg
  2005), several others do not
• Animal studies of Clostridial NF show benefit
  (Demello et al, Surgery 1973)

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