Soft Tissue Infection 1. Gas Gangrene 2. Necrotizing Fasciitis

1. Soft Tissue Infection
Nashrul Hadi

2. GAS GANGRENE
• Gas gangrene also known as "Clostridial
myonecrosis", and "Myonecrosis"
• It is a bacterial infection that produces gas in
tissues in gangrene.

3. Epidemiology
•demographics
– Male : female ratio
• no sexual predilection
•location
– buttocks, thigh, perineum

4. • risk factors
– Posttraumatic (associated with C perfringens)
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MVA (most common)
crush injuries
gunshot wounds with foreign bodies
burns and frostbite
IV drug abuse
– Postoperative
• bowel resection or perforation
• biliary surgery
• premature wound closure
– Spontaneous
• colon cancer (associated with C. septicum)
• neutropenia

5. • Pathophysiology
– Clostridial species
• Clostidium perfringens (most
common), Clostridium novyi, Clostridium
septicum
• found in soil and gut flora
• gram-positive obligate anaerobic sporeforming rods that produce exotoxins (e.g.
C. perfringens alpha toxin)
– causes muscle necrosis and vessel
thrombosis
– can cause hemolysis and shock
• incubation period <24h
• gas produced by fermentation of glucose
– main component is nitrogen
– other bacteria include E.
coli, Pseudomonas aeruginosa, Proteus
species, Klebsiella pneumoniae

6. • Prognosis
– overall 25% mortality
– 50% mortality if bacteremic
– 100% mortality if treatment is delayed
– poorer prognosis for older patients with
comorbidities.

7. Clinical Features
• History
– recent surgery to GI or biliary tract
• Symptoms
– Triad
• suddent progressive pain out of proportion to injury
– from thrombotic occlusion of large vessels
• tachycardia not explained by fever
• feeling of impending doom

8. • Physical exam
– sweet smelling odor
– swelling, edema, discoloration and ecchymosis
– blebs and hemorrhagic bullae
– "dishwater pus" discharge
– crepitus
– altered mental status

9. Investigation
Radiographs
•Findings
– linear streaks of gas in soft tissues

10. • Labs
– Elevated LDH
– Elevated WBC
– Metabolic acidosis and renal failure
• Histology
– Gram stain reveals Gram-positive bacilli
– absence of neutrophils
• lack of acute inflammatory response is hallmark
of gas gangrene
• Culture
– blood culture rarely grows Clostridial species
• DDx
– Necrotizing Fasciitis

11. Treatment
• Nonoperative
– high dose IV antibiotics
• 1st line is penicillin G and clindamycin
• alternative treatment is erythromycin, tetracycline or ceftriaxone
– clindamycin and tetracycline inhibit toxin synthesis
– hyperbaric O2
• indications
– useful adjunct
• outcomes
– effectiveness of HBO2 is inconclusive
• Operative
– radical surgical debridement with fasciotomies
• indications
– 1st line treatment is surgical

12. Complication
• Shock
• Renal failure
– both mediated by TNF alpha, IL-1, IL-6

13. NECROTIZING FASCIITIS
INTRODUCTION:
•Necrotizing fasciitis is a rapidly progressive
inflammatory infection of the fascia, with
secondary necrosis of the sub cutaneous tissue.
•It is a life threatening infection that spreads
along soft tissue planes.

14. • Risk factors
– immune suppression
• diabetes
• AIDS
• cancer
– bacterial introduction
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IV drug use
hypodermic therapeutic injections
insect bites
skin abrasions
abdominal and perineal surgery
– other host factors
• obesity
• Associated conditions
– cellulitis
• overlying cellulitis may or may not be present

15. • Prognosis
– life threatening infection
• mortality rate of 32%
• mortality correlates with time to surgical intervention

16. Necrotizing Fasciitis Classification
Type
Organism
Characteristics
Type 1
Polymicrobial
Typical 4-5 aerobic and
anerobic species cultured:
• non-Group A Strep
• anaerobes including Clostridia
• facultative anaerobes
• enterobacteria
• Synergistic virulence between
organisms
• Most common (80-90%)
• Seen in immunosuppressed (diabetics and
cancer patients)
• Postop abdominal and perineal infections
Type 2
Monomicrobial
• Group A β-hemolytic Streptococci is
most common organism isolated
Type 3
Marine Vibrio vulnificus
(gram negative rods)
Type 4
MRSA
• 5% of cases
• Seen in healthy patients
• Extremities
• Marine exposure

17. Clinical Features
• Symptoms
– early
• localized abscess or cellulitis with
rapid progression
• minimal swelling
• no trauma or discoloration
– late findings
• severe pain
• high fever, chills and rigors
• tachycardia

18. • Physical exam
– skin bullae
– discoloration
• ischemic patches
• cutaneous gangrene
– swelling, edema
– dermal induration and erythema
– subcutaneous emphysema (gas producing
organisms)
• DDx
– Gas Gangrene

19. Investigation
• Radiographs
– not required for diagnosis or treatment
• Biopsy
– only method of definitive diagnosis
– surgical intervention should not be delayed to
obtain

20. • LRINEC Score
– score > 6 has PPV of 92% of having necrotizing fasciitis
– CRP (mg/L) ≥150: 4 points
– WBC count (×103/mm3)
• <15: 0 points
• 15–25: 1 point
• >25: 2 points
– Hemoglobin (g/dL)
• >13.5: 0 points
• 11–13.5: 1 point
• <11: 2 points
– Sodium (mmol/L) <135: 2 points
– Creatinine (umol/L) >141: 2 points
– Glucose (mmol/L) >10: 1 point

21. Management
• Operative
– Emergency radical debridement with broadspectrum IV antibiotics
• indications
– whenever suspicion for necrotizing fascitis
• operative findings
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liquified subcutaneous fat
dishwater pus
muscle necrosis
venous thrombosis
• technique
– hemodynamic monitoring with systemic resuscitation is
critical
– hyperbaric oxygen chamber if anaerobic organism identified

22. – antibiotics
• initial antibiotics
– start empirically with penicillin, clindamycin, metronidazole,
and an aminoglycoside
• definitive antibiotics
– penicillin G
» for strep or clostridium
– imipenem or doripenem or meropenem
» for polymicrobial
– add vancomycin or daptomycin
» if MRSA suspected
02/05/14

23. – Amputation
• indications
– low threshold for amputation when life threatening

24. Reference
• Orthobullet
02/05/14