1. 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

2. Is it a Necrotizing Soft Tissue Infection?
CASE 1: 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: yof c/o a stiff right arm and a small cut on the right dorsal ring finger after skiing for one day.
CASE 3: yom with diabetes, PVD, c/o fever, altered mental status and black purulent vessicles on his scrotum and perineum.

4. 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”

5. 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%

6. Classification of NSTIs
Type I are polymicrobial (78-92%)
organisms per wound culture
Type II are monomicrobial (8-12%)
Group A streptococcus
Staphylococcus
Clostridium

7. Type I vs II Necrotizing Fasciitis infective agents
Type II
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

8. 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

9. 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

10. 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;224:672
Wall et al. J Am Coll Surg 2000;191:227

11. Diagnostic Lab Testing for NSTI
Wall et al. J Am Coll Surg 2000;191:
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

12. Diagnostic Lab Testing for NSTI
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%)

13. Diagnostic Lab Testing for NSTI
Pitfalls
Retrospective, case-control study
Retrospective validation
Wall et al. J Am Coll Surg 2000;191:227

14. 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

15. Minimum Standard of Care
Antibiotics
Surgical Debridement

16. Antibiotic Choices Empiric! Cover all the Bases Tetanus Status?
Triple therapy should be standard
Penicillin G
Aminoglycoside
Clindamycin/Metronidazole

17. Choices for Surgeon
You’re on your own….

18. 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

19. 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

20. Evidence for HBO and NSTI’s
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
Small patient numbers
No severity of illness scoring system

21. 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: 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

22. 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

23. 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

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

25. Algorithmic Approach to R/O NSTI
Suspicion
Low
No hard signs
High
Any Hard Sign
Intermediate
Antibiotics for staph/strep
Admit and observe Or
D/C with f/u wound check
Triple antibiotics
Surgical consultation
WBC > 15
Na+ < 135
Surgical exploration
MRI
?IV IgG for possible STTS

26. My patient has a Necrotizing Soft Tissue Infection!
Should I transfer to a facility that has Hyperbaric oxygen (HBO)?

27. 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

28. 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

29. The more things change…