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Necrotizing Soft Tissue Infections, Emergency Medicine

Basics

Description

- Necrotizing soft tissue infections (NSTI) are infections of any layer of the skin associated with necrotizing changes - Usually spreads rapidly along tissue planes

- Type I NSTI: - Polymicrobial - Anaerobic and aerobic - Include Fournier gangrene and Ludwig angina - After surgical procedures - Existing diabetes, peripheral vascular disease, chronic kidney disease, alcohol abuse - Compromised immune system

- Represent 80% of NSTIs - Strep species are most common aerobes - Also staph, enterococci, and gram-negative rods

- Type II NSTI: - Monomicrobial - Typically aerobic Streptococcus - Often young, healthy patients - Most common cause of "flesh eating " disease - Methicillin-resistant Staphylococcus aureus (MRSA) species are becoming more common

- Type III NSTI - Least common NSTI (<5%) - Rapidly progressive - Clostridial myonecrosis is an example - Usually following penetrating wounds or crush injuries - Also can be seen after black tar heroin injection, skin popping, intestinal surgery, obstetrical complications

- Neonates: Omphalitis and circumcision are predisposing factors. - Risk factors for children: - Chronic illness - Surgery - Recent varicella infection (58-fold increased risk of GABHS NSTI) - Congenital and acquired immunodeficiencies

- Fever - Altered mental status - Chronic medical conditions - IV drug use - Skin: - Rapid progression of pain and swelling of involved area - In 1st 24 hr, rapid development of local swelling, heat, erythema, and tenderness - 24 " 48 hr: Purple and blue discoloration, blisters and bullae develop (often hemorrhagic) - Foul-smelling thin fluid (from necrosis of fat and fascia)

- Pain out of proportion to physical findings - Skin: - Erythema - Tense edema - Grayish or other discolored wound drainage - Vesicles or bullae - Necrosis - Ulcers - Crepitus (pathognomonic but present in only 10 " 37% of cases) - Pain that extends past margin of infection

- US: - Fascial thickening - Fluid in the fascial plane - SC soft tissue edema

  • Necrotizing soft tissue infections (NSTI) are infections of any layer of the skin associated with necrotizing changesUsually spreads rapidly along tissue planes
  • Characterized by:Widespread fascial and muscle necrosis with relative sparing of the skinHigh mortalitySystemic toxicity
  • Crepitant anaerobic cellulitis:Necrotic soft tissue infection with abundant connective tissue gas
  • Progressive bacterial gangrene:Slowly progressive erosion affecting the total thickness of skin but not involving deep fascia
  • Nonclostridial myonecrosis (synergistic necrotizing cellulitis):Aggressive soft tissue infection of skin, muscle, SC tissue, and fascia
  • Fournier gangrene:Mixed aerobic " anaerobic soft tissue necrotizing fasciitis of the skin of the scrotum and penis in men and the vulvar and perianal skin in women
  • Necrotizing fasciitis:Progressive, rapidly spreading infection with extensive dissection and necrosis of the superficial and deep fascia
  • Accounts for 500 " 1,500 cases per year in US
  • Often difficult to recognize
  • Incidence increases with:AgeSmokingChronic systemic disease:DiabetesObesityPeripheral vascular diseaseAlcohol abuseIV drug use
  • 24 " 34% mortality
  • Also high morbidity:

Etiology

  • Conditions that lead to the development of NSTIs:Local tissue trauma with bacterial invasionLocal ischemia and reduced host defenses:More frequently in diabetics, alcoholics, immunosuppressed patients, IV drug users, and patients with peripheral vascular disease
  • Type I NSTI:PolymicrobialAnaerobic and aerobicInclude Fournier gangrene and Ludwig anginaAfter surgical proceduresExisting diabetes, peripheral vascular disease, chronic kidney disease, alcohol abuseCompromised immune systemRepresent 80% of NSTIsStrep species are most common aerobesAlso staph, enterococci, and gram-negative rodsBacteroides are most common anaerobes
  • Type II NSTI:MonomicrobialTypically aerobic StreptococcusOften young, healthy patientsMost common cause of "flesh eating " diseaseMethicillin-resistant Staphylococcus aureus (MRSA) species are becoming more common
  • Type III NSTILeast common NSTI (<5%)Rapidly progressiveClostridial myonecrosis is an exampleUsually following penetrating wounds or crush injuriesAlso can be seen after black tar heroin injection, skin popping, intestinal surgery, obstetrical complications
  • Bacteria involved include:Group A ²2-hemolytic streptococcus (GABHS)Group B streptococcusStaphylococciEnterococciBacillusPseudomonasEscherichia coliProteusKlebsiellaEnterobacterBacteroidesPasteurella multocidaClostridium sp.Vibrio sp.Aeromonas sp.Fungi
  • Neonates: Omphalitis and circumcision are predisposing factors.
  • Risk factors for children:Chronic illnessSurgeryRecent varicella infection (58-fold increased risk of GABHS NSTI)Congenital and acquired immunodeficiencies

Diagnosis

Signs and Symptoms

History

  • Fever
  • Altered mental status
  • Chronic medical conditions
  • IV drug use
  • Skin:Rapid progression of pain and swelling of involved areaIn 1st 24 hr, rapid development of local swelling, heat, erythema, and tenderness24 " 48 hr: Purple and blue discoloration, blisters and bullae develop (often hemorrhagic)Foul-smelling thin fluid (from necrosis of fat and fascia)

Physical Exam

  • Systemic toxicity:FeverTachycardiaTachypneaHypotensionAltered mental status
  • Pain out of proportion to physical findings
  • Skin:ErythemaTense edemaGrayish or other discolored wound drainageVesicles or bullaeNecrosisUlcersCrepitus (pathognomonic but present in only 10 " 37% of cases)Pain that extends past margin of infection
  • Most common presenting symptomsLocalized pain (97%)Rash (73%)Hypotension, altered mental status, and other signs of shock are much less common

Essential Workup

  • Diagnosis can be difficult
  • Careful exam for the aforementioned signs and symptoms in high-risk patients
  • NSTIs must be suspected in patients who appear very ill and have pain out of proportion to physical findings
  • Diagnosis may require incision and probing of tissue

Diagnosis Tests & Interpretation

Lab

  • CBC with differential
  • Electrolytes
  • BUN and creatinine
  • Disseminated intravascular coagulation panel
  • Calcium level: Hypocalcemia can develop from extensive fat necrosis
  • Gram stain and aerobic/anaerobic cultures of wound or tissue biopsy

Imaging

  • X-rays to detect soft tissue gas: Pathognomonic, but present in only 39 " 57% of cases
  • CT scan:May be more helpful than plain x-rays in detecting SC airMay also identify deep abscess or other cause of infection
  • MRI:Can delineate extent of spread of the infection
  • US:Fascial thickeningFluid in the fascial planeSC soft tissue edema

Imaging of any kind should never delay surgical debridement

Diagnostic Procedures/Surgery

  • All patients with suspected NSTI must undergo surgical debridement
  • Deep incisional biopsy and cultures are the gold standard for diagnosis

Differential Diagnosis

Treatment

Pre-Hospital

  • IV fluid resuscitation
  • Manage airway as necessary.

Initial Stabilization/Therapy

Manage airway and resuscitate as indicated:

  • Rapid-sequence intubation as needed
  • Supplemental oxygen, monitor, evaluate for acid " base disturbances
  • IV access, CVP line may be needed
  • Aggressive volume expansion including crystalloid, plasma, packed RBCs, and albumin

Ed Treatment/Procedures

  • Antibiotics: Broad coverage of aerobic gram-positive and gram-negative organisms and anaerobes
  • Acceptable combination therapy:Penicillin or cephalosporin + an aminoglycoside or fluoroquinolone + anaerobic coverage with either clindamycin or metronidazole
  • Treat methicillin-resistant Staphylococcus aureus (MRSA) until excluded:VancomycinLinezolidDaptomycin
  • Surgical consultation:Early debridement of all necrotic tissue with fasciotomy and drainage of fascial planes is paramount
  • Hyperbaric oxygen as an adjunct:Early transfer to hyperbaric facility may result in greater tissue salvage
  • IV immunoglobulin (IVIG):ControversialMay be beneficial in NSTI caused by group A streptococcal infection
  • Observe for major complications including acute respiratory distress syndrome, renal failure, myocardial irritability, and DIC

Clindamycin therapy should be initiated as soon as possible when group A strep infection is suspected

Medication

  • Ceftriaxone: 2 g (peds: 100 mg/kg/24 h; max. 4 g) IV q24h
  • Ciprofloxacin: 400 mg IV q12h
  • Clindamycin: 900 mg (peds: 40 mg/kg/d q6h) IV q8h
  • Daptomycin: 4 mg/kg IV q24h
  • Gentamicin: 2 mg/kg (peds: 2 mg/kg IV q8h) IV q8h
  • Doxycycline: 100 mg IV q12h
  • Imipenem/cilastatin: 250 " 1,000 mg IV q6 " 8h
  • Levofloxacin: 750 mg IV q24h
  • Linezolid: 600 mg PO/IV q12h (peds: 30 mg/kg/d PO/IV div. q8h)
  • Meropenem: 1 g (peds: 20 " 40 mg/kg up to 2 g/dose) IV q8h
  • Metronidazole: 500 mg (peds: Safety not established) IV q8h
  • Penicillin G: 24 million U q24h (peds: 250,000 IU/kg/24h) IV q4 " 6h
  • Piperacillin/tazobactam 3.375 " 4.5 g (peds: 240 mg/kg/d of piperacillin div. q8h) IV q6h
  • Tigecycline: Start 100 mg IV 1; 50 mg IV q12h
  • Vancomycin: 10 " 15 mg/kg IV q12h (peds: 10 " 15 mg/kg IV q6 " 8h)

First Line

  • Type I infections:Piperacillin/tazobactam + clindamycin + ciprofloxacin/levofloxacinImipenem/cilastatinMeropenem
  • Type II infections:Clindamycin + penicillin (or linezolid or vancomycin)
  • Type III infections:
  • Type IV infections:

Follow-Up

Disposition

Admission Criteria

  • All patients with an NSTI must be admitted for surgical debridement and IV antibiotics
  • Early hyperbaric oxygen therapy may be an important adjunct

Discharge Criteria

No patient with NSTI should be discharged

Issues for Referral

After stabilization with antibiotics and surgical debridement, consider referral for hyperbaric oxygen treatment as an adjunct.

Pearls and Pitfalls

  • The clinician must have a high index of suspicion for NSTI, as initial skin findings may be unimpressive
  • Pain out of proportion to exam may be a key finding
  • Mortality will be near 100% if treatment is ONLY with antimicrobials
  • Scoring systems for NSTI have limited utility
  • 4 tenets of treating NSTI:Fluid resuscitation and management of metabolic disturbancesEarly antimicrobial therapySurgical debridementTreating organ failure

Additional Reading

  • Anaya DA, Bulger EM, Kwon YS, et al. Predictingdeath in necrotizing soft tissue infections: A clinical score. Surg Infect(Larchmt). 2009;10:517 " 522.
  • Anaya DA, Dellinger EP. Necrotizing soft-tissue infection: Diagnosis and management. Clin Infect Dis. 2007;44:705 " 710.
  • Cainzos M, Gonzalez-Rodriguez FJ. Necrotizing soft tissue infections. Curr Opin Crit Care. 2007;13:433 " 439.
  • Jamal N, Teach SJ. Necrotizing fasciitis. Pediatr Emer Care. 2011;27:1195 " 1199.
  • Lancerotto L, Tocco I, Salmaso R, et al. Necrotizingfasciitis: Classification, diagnosis, and management. J Trauma Acute CareSurg. 2012;72:560 " 566.
  • Ustin JS, Malangoni MA. Necrotizing soft-tissue infections. Crit Care Med. 2011;39:2156 " 2162.

See Also (Topic, Algorithm, Electronic Media Element)

  • Cellulitis
  • Erysipelas
  • MRSA, Community Acquired
  • Gangrene

Codes

ICD9

  • 608.83 Vascular disorders of male genital organs
  • 728.86 Necrotizing fasciitis
  • 785.4 Gangrene
  • 729.99 Other disorders of soft tissue
  • 616.89 Other inflammatory disease of cervix, vagina and vulva

ICD10

  • I96 Gangrene, not elsewhere classified
  • N49.3 Fournier gangrene
  • M72.6 Necrotizing fasciitis
  • M79.89 Other specified soft tissue disorders
  • N76.89 Other specified inflammation of vagina and vulva

SNOMED

  • 52486002 Necrotizing fasciitis (disorder)
  • 398318005 Fourniers gangrene
  • 372070002 Gangrenous disorder (disorder)
  • 443928008 Necrotizing soft tissue infection