Necrotizing soft tissue infections

Background

• Includes necrotizing forms of cellulitis, myositis, and fasciitis
• Two types:
  • Type 1: polymicrobial infection
  • Type 2: group A strep
    • May occur in healthy individuals
    • May occur via hematogenous spread from throat to site of blunt trauma

Necrotizing Fasciitis

Risk Factors

• DM
• Drug use
• Obesity
• Immunosuppression
• Recent surgery
• Traumatic wounds

Clinical Features

• Skin exam
  • Erythema (without sharp margins)
  • Exquisitely tender (pain out of proportion to exam)
  • Skip lesions
  • Hemorrhagic bullae
    • May be preceded by skin anesthesia (destruction of superficial nerves)
  • Crepitus (in type I infections)
• Swelling/edema may produce compartment syndrome
• Constitutional
  • Fever
  • Tachycardia
  • Systemic toxicity

Work-Up

• CBC
• Chem
• PT/PTT/INR
• CK
• Lactate

Diagnosis

• Surgical exploration is the ONLY way to definitively establish the diagnosis of necrotizing infection
• Imaging
  • Should not delay surgical exploration
  • CT is study of choice

Treatment

• Surgical exploration and debridement
  • Indicated in setting of severe pain, toxicity, fever, elevated CK, w/ or w/o radiographic evidence
• Abx
  • Must cover Gram +/- and anaerobes (esp GAS and clostridium)
  • Piperacillin-tazobactam 3.375-4.5g q6hr AND clindamycin 600-900mg q8hr AND vancomycin 1gm IV q12hr

Necrotizing Myositis

Background

• Much rarer than nec fasc
• May be preceded by skin abrasions, blunt trauma, heavy exercise
• Most patients are otherwise healthy (DM and other underlying conditions do not appear to increase risk)

Clinical Features

• Exquisite pain and swelling of affected muscle with induration
• Overlying skin changes may manifest later in the course of illness (erythema, warmth, petechiae, bullae)
• Hypotension may occur rapidly with development of streptococcal toxic shock syndrome

Management

• Same as necrotizing fasciitis (see above)

Necrotizing Cellulitis

Background

• Pts are often much less toxic compared with nec fasc/nec myo
• Two types:
  • Anaerobic infection (clostridial and nonclostridial)
  • Meleney's synergistic gangrene
    • Rare infection that occurs in postop pts
    • Characterized by slowly expanding indolent ulceration that is confined to superficial fascia
    • Results from synergistic interaction between S. aureus and microaerophilic streptococci

Risk Factors

• Trauma
• Surgical contamination
• Spread of infection from bowel to perineum, abdominal wall, or lower extremities

Clinical Features

• Thin, dark, sometimes foul-smelling wound drainage (often containing fat globules)
• Tissue gas formation (crepitus)

Management

• Same as necrotizing fasciitis (see above)

Source

• UpToDate