Soft Tissue Infection Nashrul Hadi
May 25, 2015
Soft Tissue Infection
Nashrul Hadi
GAS GANGRENE
• Gas gangrene also known as "Clostridial myonecrosis", and "Myonecrosis"
• It is a bacterial infection that produces gas in tissues in gangrene.
Epidemiology•demographics– Male : female ratio• no sexual predilection
•location– buttocks, thigh, perineum
• risk factors– Posttraumatic (associated with C perfringens)
• 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
• Pathophysiology– Clostridial species
• Clostidium 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) – 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
• Prognosis– overall 25% mortality – 50% mortality if bacteremic– 100% mortality if treatment is delayed– poorer prognosis for older patients with
comorbidities.
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
• Physical exam– sweet smelling odor– swelling, edema, discoloration and ecchymosis– blebs and hemorrhagic bullae– "dishwater pus" discharge– crepitus– altered mental status
Investigation
Radiographs•Findings– linear streaks of gas in soft tissues
• 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
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
Complication
• Shock• Renal failure– both mediated by TNF alpha, IL-1, IL-6
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.
• Risk factors– immune suppression
• diabetes• AIDS• cancer
– bacterial introduction• 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
• Prognosis– life threatening infection• mortality rate of 32%• mortality correlates with time to surgical intervention
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
• 5% of cases • Seen in healthy patients • Extremities
Type 3 Marine Vibrio vulnificus(gram negative rods)
• Marine exposure
Type 4 MRSA
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
• Physical exam– skin bullae– discoloration • ischemic patches• cutaneous gangrene
– swelling, edema– dermal induration and erythema– subcutaneous emphysema (gas producing
organisms)
• DDx– Gas Gangrene
Investigation
• Radiographs– not required for diagnosis or treatment
• Biopsy – only method of definitive diagnosis– surgical intervention should not be delayed to
obtain
• 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
Management• Operative– Emergency radical debridement with broad-
spectrum IV antibiotics • indications
– whenever suspicion for necrotizing fascitis• operative findings
– liquified subcutaneous fat– dishwater pus– muscle necrosis– venous thrombosis
• technique– hemodynamic monitoring with systemic resuscitation is
critical– hyperbaric oxygen chamber if anaerobic organism identified
– 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
04/12/23
– Amputation• indications
– low threshold for amputation when life threatening
Reference
• Orthobullet
04/12/23