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?

• 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.

• 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.

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

Terminology

• Best terminology is Necrotizing Soft Tissue Infection (NSTI)

• Includes:– 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

• Incidence: estimated 1000 cases/year in US

• Mortality has not changed significantly since 1924 – approximate mean mortality of 22% – range of 6-80%

Classification of NSTIs

• Type I are polymicrobial (78-92%)– 2.1-4.4 organisms per wound culture

• Type II are monomicrobial (8-12%)– Group A streptococcus– Staphylococcus– Clostridium

Type I vs II Necrotizing Fasciitis infective agents

• Bacteroides• Candida• Clostridium• Corynebacterium• Cryptococcus• Eikenella• Enterobacter• Escherichia• Fusobacterium• Histoplasma

•Klebsiella•Neisseria•Pasturella•Proteus•Salmonella•Serratia•Shigella•Staphylococcus•Streptococcus •(non Group A)•Vibrio

• Group A Streptococcus+/- Staph

Type I Type II

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

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

• Heighten suspicion with the following:– 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• Common Hard Clinical Findings??

– 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;224:672Wall et al. J Am Coll Surg 2000;191:227

Diagnostic Lab Testing for NSTI

• 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 NSTIValidation: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

• Pitfalls– Retrospective, case-control study– Retrospective validation

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

Radiographic Diagnostic Adjuncts• Plain film x-ray

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

• CT Scan/ Ultrasound– Identify air bubbles in tissue relative to fascial planes

• MRI– With Gd contrast distinguishes perfused vs necrotic

tissue– Defines extent of disease, may help guide surgical

approach

Minimum Standard of Care

• Antibiotics

• Surgical Debridement

Antibiotic Choices

• Empiric! Cover all the Bases

• Tetanus Status?

• Triple therapy should be standard– Penicillin G– Aminoglycoside– Clindamycin/Metronidazole

Choices for SurgeonYou’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

• 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

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

Evidence for HBO and NSTI’sHollabaugh, 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– Small patient numbers– No severity of illness scoring system

Evidence not supporting HBO in NSTI

• 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

– HBO vs control: 30 vs 42%

• Pitfalls– 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

• 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

– 28 vs 48 days

• Pitfalls– Retrospective uncontrolled study

Possible Adjunctive Therapies

• Polyspecific i.v. IgG• Rationale of usage: Strep/staph infections common in NSTI (58%) “Superantigen” toxins commonly secrteted

during infection and cause toxic shock Polyspecific i.v. IgG contains antibodies

neutralizing superantigens Individuals with serious strep NSTIs lack

neutralizing antibodies to superantigens

Antigen presenting cell

MHC-II

Antigen

Superantigen

T-cell

T-cell Antigenreceptor

Cytokineproduction

Algorithmic Approach to R/O NSTI

Suspicion

HighAny Hard Sign

LowNo hard signs

Antibiotics for staph/strepAdmit and observe

Or

Antibiotics for staph/strepD/C with f/u wound check

Triple antibioticsSurgical consultation

Surgical explorationMRI?IV IgG for possible STTS

WBC > 15Na+ < 135

Intermediate

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

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

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

The more things change…