Necrotizing Fasciitis

12 May, 11

Necrotizing Fasciitis: Interesting Reading
An Infection on Skin Often Looks Benign, May Quickly Turn Into Deadly Systemic Illness

Necrotizing Fasciitis

A dangerous infection of soft-tissue that starts in the subcutaneous tissue and spreads along the flat layers of fibrous tissue that separate different layers of tissue (fascial planes). It most commonly occurs in the arms, legs and abdominal wall. The death rate is up to 40%.

Necrotizing fasciitis can be monomicrobial or polymicrobial. Monomicrobial infections account for 10% and polymicrobial for 90% of cases of necrotizing fasciitis.

Symptoms include erythema, edema and tenderness. The degree of pain typically is greater than the severity of these findings and the person appears terribly ill. The original skin wound is often evident. Skin changes may include bullous lesions (blisters) and local skin anesthesia (due to blocking of little vessels in the skin). A crinkly or crackling feeling called crepitus indicates gas in the tissues but occurs in only about half of cases.

Emergency diagnosis and treatment are essential. Broad-spectrum antibiotic treatment and prompt surgical removal of dead and infected tissue decreases the death rate.

Pathogens

Mixed aerobic-anaerobic bacteria
Group A streptococcus (GAS), S. pyogenes
Clostridium perfringens
Community -acquired MRSA
Vibrio vulnificus

Clinical Examination

Infection extending along fascial plane-usually an extremity, perianal area. genitals (Fournier's).

Clinical

Severe pain, severe systemic toxicity, process with rapid spread, fever, skin necrosis with bullae, tense edema &/or black-blue discoloration.

Some patients havepreceding injury orsurgery; some do not.

Differential Diagnosis

?Cellulitis: treated with antibiotics and NO surgery (big difference).
Gas gangrene,
Vibrio vulnificus,
Soft tissue infection
Myositis

3 Major Bacterial Patterns

Pus with anaerobic infection is "dishwater gray," has a characteristic putrid smell & gram stain/culture of pus shows mixed flora.
Group A streptococci, mixed anaerobes + coliforms, or MRSA. Distinguish by GS & culture of exudate, bullae, aspirate or blood.
Mixed anaerobic infections are most common form--also requires rapid surgery.
Host specific etiologies

Diabetes, steroids: mucormycosis
Burns, neutropenia: Pseudomonas gangrenous cellulitis
Exposure to aquacultured fish: Streptococcus iniae
Exposure to fresh/brackish waters: Aeromonas spp & Vibrio vulnificus
Systemic infection: N. meningitidis, Ps. aeruginosa

Diagnosis

Lab: CT scan or MRI showing fascial plane infection. Some patients should not be delayed by imaging studies, but rather have rapid surgical consultation and proceed to operating room.

Treatment

Antibiotic Treatment

Principles: diagnosis by CT/MRI or surgery. Surgery urgent. Antibiotics against streptococci (clindamycin) or anaerobes + coliforms (e.g., intra-abdominal sepsis regimens) and MRSA (vancomycin, clindamycin or linezolid).
Empiric regimen: Linezolid 600 mg IV q12h + either meropenem 1 gm IV q 8h or piperacillin/tazobactam 3.375 gm IV q 6h.
Mixed infection with coliforms + anaerobes (preferred): cefotaxime 2-4gm IV q8h + either clindamycin 600mg IV q 8h or metronidazole 500mg IV/PO q6h.
Alternative: ampicillin/sulbactam 1.5-3g IV q6h or piperacillin/tazobactam or ticarcillin/clavulanate or imipenem.
Group A streptococci: clindamycin 600mg IV q8h + penicillin 2-4 million units IV q4h.
Community acquired MRSA: linezolid 600 mg IV q12h or vancomycin 1 gm IV q 12h.
Modify antibiotic regimen when the pathogen is defined: 1) Streptococci: give clindamycin + penicillin, 2) mixed anaerobes + coliforms: use regimen for

Surgery

Incision + debridement mandatory.
May require daily re-debridements.

Other Treatment

Supportive care: hydration, treatment of renal failure, wound care.
Hyperbaric oxygen: merit is debated. Problem is transfer of seriously ill patient & uncertain benefit.
Hyperbaric oxygen (cont'd): possible benefit = surgeons affiliated w/ facilities often expert regarding management of serious soft tissue infections, especiallythe need for extensive surgery and reoperation.
Toxic-shock (streptococcal): Intravenous gamma globulin (>2 batches: some use 50g/dose, others 0.4g/kg q6h IV).
Infection control: Group A streptococci and S. aureus (MRSA), use contact precautions.
Infection control: some consider Gr A streptococci transferable to family members, household contacts & healthcare workers, but risk is small.

Drug Comments

Follow Up

Causes for Alarm with Soft Tissue Infection

Severe pain
Systemic toxicity
Bullae
Cutaneous necrosis
Gas in tissue
Tense edema

Other Information

Immediate therapy

Initiate antibiotics against streptococci (clindamycin +/-penicillin) and anaerobes/coliforms (regimens for intra-abdominal sepsis) and MRSA (clindamycin+/-linezolid/vancomycin).
Need surgery ASAP.
If time available, obtain CT can or MRI to define extent of problem.