NECROTIZING FASCITIS

NECTROTIZING FASCITIS
GAS GANGRENE

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. E tiology

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 (×10 3 /mm 3 ) <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

14. 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

15. Gas gangrene

16. D efinition 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.

17. 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 )

18. E tiology 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

19. 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

20. workup Laboratory Cultures I maging

21. Radiographs findings linear streaks of gas in soft tissues

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

23. 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

24. 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