This document discusses necrotizing fasciitis and gas gangrene. It defines necrotizing fasciitis as a necrotizing soft tissue infection along fascial planes that can present with disproportionate pain and swelling. Risk factors include diabetes and immunosuppression. Treatment involves broad-spectrum antibiotics and urgent debridement. Gas gangrene is caused by Clostridium bacteria, often after trauma. It presents with pain, swelling and crepitus, and is treated with antibiotics and radical debridement to remove necrotic muscle. Imaging may show gas in tissues. Both conditions require prompt recognition and aggressive treatment to prevent mortality.

1. Necrotizing fasciitis

2. • Definition
• Risk factors
• Etiology
• Pathogenesis
• Microbiology
• Clinical presentation
• Workup
• Management
• Prognosis

3. Definition
• Necrotizing fasciitis is a necrotizing soft tissue infection spreading
along fascial planes with or without overlying cellulitis.

4. •Diabetes
•Chronic disease
•Immunosuppressive drugs (eg, prednisolone)
•Malnutrition
•Age > 60 years
•Intravenous drug misuse
•Peripheral vascular disease
•Renal failure
•Underlying malignancy
•Obesity
Risk factors
bacterial introduction
IV drug use
hypodermic therapeutic injections
insect bites
skin abrasions
abdominal and perineal surgery

5. Etiology

6. Clinical presentation
• Patients with NF can present with
• constitutional symptoms of sepsis (eg, fever, tachycardia, altered mental
state)
• signs of skin inflammation (ie, pain, skin edema, and erythema)
• However, as these are also present in less serious conditions such as
cellulitis, the degree of pain relative to the skin condition might
provide the physician with clues—NF typically presents with pain out
of proportion to the degree of skin inflammation.

7. • Necrotizing fasciitis typically presents with patchy discolouration of
the skin with pain and swelling, but without a defined margin
• Progression of NF is marked with the development of tense edema, a
grayish-brown discharge, vesicles, bullae, necrosis, and crepitus

8. Workup
• Laboratory
• Cultures
• Imaging

9. Laboratory risk indicator for NF (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

10. Cultures
• Blood cultures
• Intraoperative tissue cultures

11. Imaging
• The common plain radiographic findings non-specific with increased soft-
tissue thickness and opacity. Radiographs can be normal until the advanced
stages of infection and necrosis. The characteristic finding of gas in the soft
tissues is seen in only a minority of cases
• imaging plays a very limited role in diagnosis and management of necrotising
fasciitis.

12. Treatment
• Antibiotics
• Operative

13. 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

15. Operative
• emergency radical debridement with broad-spectrum IV antibiotics
operative findings
• liquefied subcutaneous fat
• dishwater pus
• muscle necrosis
• venous thrombosis
• noncontracting muscle,
• and a positive “probe test” result, which is characterized by lack of resistance to finger
dissection in normally adherent tissues

16. Gas gangrene

17. Definition
• necrotizing soft tissue infection of skeletal muscle caused by toxin-
and gas-producing Clostridium species.
• The synonym clostridial myonecrosis better describes both the
causative agent and the target tissue.

18. Risk factors
• risk factors
• posttraumatic (associated with C perfringens)
• car accidents (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)

19. Etiology
Clostridial species
• Clostridium perfringens (most common),
• Clostridium novyi
• Clostridium septicum
found in soil and gut flora
• gram-positive obligate anaerobic spore-forming rods that produce exotoxins (e.g.
C. perfringens alpha toxin)
• gas produced by fermentation of glucose
• other bacteria include E. coli, Pseudomonas aeruginosa, Proteus
species, Klebsiella pneumoniae

20. Clinical presentation
• History
• recent surgery to GI or biliary tract
• Symptoms
• triad
• sudden progressive pain out of proportion to injury
• from thrombotic occlusion of large vessels
• tachycardia not explained by fever
• feeling of impending doom
• Physical exam
• sweet smelling odor
• swelling, edema, discoloration and ecchymosis
• blebs and hemorrhagic bullae
• "dishwater pus" discharge
• crepitus

21. workup
• Laboratory
• Cultures
• Imaging

22. Radiographs
• findings
• linear streaks of gas in soft tissues

23. Labs
• Elevated WCC
Histology :
• Gram stain reveals Gram-positive bacilli
Culture
• blood culture rarely grows Clostridial species
• Intraoperative tissue, muscle cultures

24. treatment
Antibiotics
• high dose IV antibiotics
• 1st line is penicillin G and clindamycin
• alternative treatment is erythromycin, tetracycline or ceftriaxone
• clindamycin and tetracycline inhibit toxin synthesis
Operative
• radical surgical debridement with fasciotomies
Intraoperative
• Non viable muscle, myonecrosis

26. references
• https://www.orthobullets.com/trauma/1007/necrotizing-fasciitis
• https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2762295/
• https://radiopaedia.org/cases/gas-gangrene-of-lower-limb
• https://www.orthobullets.com/trauma/1067/gas-gangrene