Necrotizing Soft Tissue Infections:

Update in diagnosis and management Nathan I. Shapiro, MD, MPH Department of Emergency Medicine Beth Israel Deaconess Medical Center Boston, MA

Is it a Necrotizing Soft Tissue Infection?

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CASE 1: 36 yom with no medical problems c/o 0.5 cm laceration to the left index finger due to scraping it on a photocopier yesterday. Also has an atraumatic sore left shoulder.

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CASE 2: 42 yof c/o a stiff right arm and a small cut on the right dorsal ring finger after skiing for one day.

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CASE 3: 86 yom with diabetes, PVD, c/o fever, altered mental status and black purulent vessicles on his scrotum and perineum.

Terminology

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Best terminology is Necrotizing Soft Tissue Infection (NSTI) Includes:

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Necrotizing Fasciitis Fournier’s gangrene Clostridial “gas” gangrene or myonecrosis

• “necrotic fascia and/or muscle noted on surgery or pathologic exam of debrided tissue”

Basics of NSTIs

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Incidence: estimated 1000 cases/year in US Mortality has not changed significantly since 1924

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approximate mean mortality of 22%

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range of 6-80%

Classification of NSTIs

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Type I are polymicrobial (78-92%)

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2.1-4.4 organisms per wound culture

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Type II are monomicrobial (8-12%)

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Group A streptococcus

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Staphylococcus

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Clostridium

Type I vs II Necrotizing Fasciitis infective agents Type I

• Bacteroides • Candida • Clostridium • Corynebacterium • Cryptococcus • Eikenella • Enterobacter • Escherichia • Fusobacterium • Histoplasma •Klebsiella •Neisseria •Pasturella •Proteus •Salmonella •Serratia •Shigella •Staphylococcus •Streptococcus •(non Group A) •Vibrio

Type II

• Group A Streptococcus +/- Staph

Diagnostic challange

• Innocent beginnings • Rapid progression of disease • Lack of studies on early disease presentation or on progression of early disease • Ultimate diagnosis is made at surgical exploration

Diagnostic Modalities: Clinical Exam

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History…advanced disease easy, early disease utility requires HIGH DEGREE OF SUSPICION.

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Heighten suspicion with the following:

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Pain out of proportion to clinical lesion Tense edema Edema extends beyond erythema Purplish skin discoloration Numbness/weakness in the affected area (possible edema-induced compartment-like syndrome or directly damaged cutaneous nerves)

Wall et al. J Am Coll Surg 2000;191:227

Clinical Exam

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Common Hard Clinical Findings??

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Bullae 16-24% Necrotic skin 6-3% Crepitance 0-36% Hypotension 7-11% Gas on plain x-ray 32-57% Tense edema 23-38% Even in late presenting cases, 20-61% lack any hard clinical sign!

Elliott et al. Ann Surg 1996;224:672 Wall et al. J Am Coll Surg 2000;191:227

Diagnostic Lab Testing for NSTI

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Wall et al. J Am Coll Surg 2000;191:227-231 Wall et al Am J surg 179:2000:17-20 Retrospective case control study of 31 consecutive NSTI vs 328 non-NSTI patients Model selected by decision tree analysis on vital signs and laboratory testing Positive model demonstrated WBC>15.4 or serum Na<135

Diagnostic Lab Testing for NSTI

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Validation: WBC > 15.4 or Na < 135 in predicting NSTI 90% sensitivity (74-90%) 76% specific (71-80%) Positive Predictive Value (18-35%) Negative Predictive Value (97-100%)

Diagnostic Lab Testing for NSTI

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Pitfalls

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Retrospective, case-control study Retrospective validation

Wall et al. J Am Coll Surg 2000;191:227

Radiographic Diagnostic Adjuncts

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Plain film x-ray

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May demonstrate gas in tissues (39-75% of cases) Negative predictive value 62% in Wall et al.

CT Scan/ Ultrasound

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Identify air bubbles in tissue relative to fascial planes MRI

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With Gd contrast distinguishes perfused vs necrotic tissue Defines extent of disease, may help guide surgical approach

Minimum Standard of Care

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Antibiotics

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Surgical Debridement

Antibiotic Choices

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Empiric! Cover all the Bases Tetanus Status?

Triple therapy should be standard

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Penicillin G

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Aminoglycoside

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Clindamycin/Metronidazole

Choices for Surgeon

You’re on your own….

Possible Adjunctive Therapies

• Hyperbaric oxygen (HBO) – Directly toxic to certain anerobes (clostridium) – Improved infection site tissue oxygen tension improves neutrophil bacteriocidal activity – Case series suggest possible improvements in mortality, number of surgeries required, wound closure rates

Evidence for HBO and NSTI’s

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Riseman, et al. Surgery 1990;108:847 Group 1: 12 std of care vs Group 2: 17 +HBO (before and after study) Mortality reduced with HBO, 23 vs 66% Reduced operative debridements, 1.2 vs 3.3

Pitfalls

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Small patient numbers No illness severity scoring system Includes more perineal infections in Group 2

Evidence for HBO and NSTI’s

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Hollabaugh, et al. Plast Reconstr Surg. 1998;101:94.

Group 1: 12 standard of care vs Group 2: 14 +HBO Mortality reduced with HBO 7 vs 42% No difference in number of operations required Pitfalls

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Small patient numbers

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No severity of illness scoring system

Evidence not supporting HBO in NSTI

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Brown et al. Am J Surg 1994;167:485 Truncal NSTI: Std care n=24 vs +HBO n=30 APACHE II std used, NS difference in groups HBO group had more operations/patient: 3.2 vs 1.6

Mortality not significantly improved with HBO

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HBO vs control: 30 vs 42% Pitfalls

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Small number of patients 16 HBO group patients transferred for care HBO group patients younger (51 vs 63 P<0.05) Multiple centers and possible standard care variation

Evidence not supporting HBO in NSTI

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Elliot et al. Ann Surg 1996;224:672 198 patient consecutive retrospective review Groups: survivors 148 vs non-survivors n=50 No improvement in mortality with HBO: 25% Improved rate of wound closure with HBO

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28 vs 48 days Pitfalls

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Retrospective uncontrolled study

Possible Adjunctive Therapies

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Polyspecific i.v. IgG

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Rationale of usage:

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Strep/staph infections common in NSTI (58%)

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“Superantigen” toxins commonly secrteted during infection and cause toxic shock

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Polyspecific i.v. IgG contains antibodies neutralizing superantigens

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Individuals with serious strep NSTIs lack neutralizing antibodies to superantigens

T-cell Antigen receptor Antigen MHC-II T-cell Cytokine production Superantigen Antigen presenting cell

Algorithmic Approach to R/O NSTI

Suspicion Low No hard signs Intermediate High Any Hard Sign Antibiotics for staph/strep Admit and observe

WBC > 15 Na+ < 135

Or Antibiotics for staph/strep D/C with f/u wound check Triple antibiotics Surgical consultation Surgical exploration MRI ?IV IgG for possible STTS

My patient has a Necrotizing Soft Tissue Infection!

Should I transfer to a facility that has Hyperbaric oxygen (HBO)?

Evidence based survey of HBO in treating NSTIs

• There are no prospective randomized controlled studies on this subject • All information on NSTI treatment is based on retrospective case reviews • Because of the rarity, varied eitiologies and presentations of this disease, there will likely never be a gold-standard study

Role of HBO in NSTI

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Currently not sufficient data to mandate transfer of patient to HBO containing facility…do not delay surgical intervention!

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If available HBO should be considered for possible benefits on mortality and improved wound closure

The more things change…