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surgery.necrotizing-soft-tissue-infection.core.v1

Necrotizing Soft-Tissue Infection

infectious_diseaseacuteadultacuteinpatient
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NSTI — surgical emergency; mortality 20-40% even optimal. Source control (OR) is DEFINITIVE; antibiotics alone are insufficient. IDSA 2014 (Stevens PMID 24973422) is current floor. LRINEC (Wong 2004 PMID 15241098) is supportive only — never rule out with low score. Empiric triple regimen: vanc (MRSA) + pip-tazo (gram neg + anaerobic + Pseudomonas) + clindamycin (toxin suppression Eagle effect). IVIG is Class IIb for GAS TSS with refractory shock — controversial. Workup workup.cellulitis_necfasc registered in clinical-tools-registry. All PMIDs + RxCUIs live-verified 2026-05-26.

Entry points (6)

  • symptom
    Pain out of proportion to exam findings (hallmark) (IDSA 2014)
    pain_out_of_proportion
  • symptom
    Cellulitis with rapid spread, systemic toxicity, hemorrhagic bullae (IDSA 2014)
    rapidly_progressing_cellulitis
  • symptom
    Crepitus / gas in soft tissue / dishwater discharge from incision (IDSA 2014)
    crepitus_dishwater_drainage
  • symptom
    Perineal / scrotal pain + skin necrosis (Fournier gangrene) (IDSA 2014)
    fournier_perineal
  • lab_abnormality
    LRINEC score >=6 supports diagnosis (Wong 2004 PMID 15241098)
    lrinec_above_6
  • imaging
    CT showing soft tissue gas or fascial fluid/thickening (IDSA 2014)
    soft_tissue_gas_or_fascial_thickening

Required inputs (15)

  • agerequired
    demographic • used at CONTEXT
    Mortality + drug-clearance considerations (IDSA 2014)
  • temperaturerequired
    vital • used at CONTEXT
    Fever > or = 38 or hypothermia in shock (IDSA 2014)
  • sbprequired
    vital • used at RED_FLAGS
    Septic shock (toxin-mediated streptococcal TSS) drives ICU + IVIG consideration (IDSA 2014)
  • hrrequired
    vital • used at CONTEXT
    Tachycardia + hypotension = sepsis screen (IDSA 2014)
  • wbcrequired
    lab • used at INITIAL_WORKUP
    WBC >15 contributes to LRINEC; sepsis-3 component (Wong 2004 PMID 15241098)
  • sodiumrequired
    lab • used at INITIAL_WORKUP
    Hyponatremia <135 in LRINEC; common in NSTI from third-spacing (Wong 2004)
  • creatininerequired
    lab • used at INITIAL_WORKUP
    AKI from sepsis + antibiotic dosing (vanc trough, pip-tazo) (IDSA 2014)
  • crprequired
    lab • used at INITIAL_WORKUP
    CRP >150 = 4 LRINEC points; inflammation marker (Wong 2004 PMID 15241098)
  • hemoglobin
    lab • used at INITIAL_WORKUP
    Anemia / hemolysis contributes to LRINEC (Wong 2004)
  • glucose
    lab • used at INITIAL_WORKUP
    Hyperglycemia >180 in LRINEC; diabetic risk factor (Wong 2004)
  • lactate
    lab • used at RED_FLAGS
    Sepsis severity; hypoperfusion marker (IDSA 2014)
  • diabetes_mellitus
    history • used at CONTEXT
    Major risk factor for NSTI; alters empiric coverage (IDSA 2014)
  • immunocompromise
    history • used at CONTEXT
    Cirrhosis / CKD / cancer / steroids / IVDU drive empiric breadth (IDSA 2014)
  • water_or_seafood_exposure
    history • used at CONTEXT
    Vibrio vulnificus exposure -> add doxycycline + ceftriaxone (IDSA 2014)
  • recent_skin_trauma_surgery
    history • used at CONTEXT
    Portal of entry / postoperative wound infection (IDSA 2014)

12-phase flow (12)

  1. 1FRAME
    Confirm NSTI suspicion; distinguish from severe non-necrotizing cellulitis / abscess (IDSA 2014)
    inputs: age, diabetes_mellitus
    advance: NSTI in differential
  2. 2ENTRY
    Pain out of proportion / crepitus / hemorrhagic bullae / rapidly progressive cellulitis / systemic toxicity (IDSA 2014)
    advance: one red-flag finding triggers workup
  3. 3CONTEXT
    Risk factors (DM, immunocompromise, water exposure, trauma); meds; allergies (IDSA 2014)
    inputs: temperature, hr, diabetes_mellitus, immunocompromise, water_or_seafood_exposure, recent_skin_trauma_surgery
    advance: context captured
  4. 4RED_FLAGS
    Septic shock + skin necrosis + crepitus + systemic toxicity = STAT surgical consult (do NOT wait for imaging) (IDSA 2014)
    inputs: sbp, lactate, wbc
    actions: calc.qsofa, workup.cellulitis_necfasc
    advance: shock identified or excluded
  5. 5INITIAL_WORKUP
    CBC, BMP, LFTs, lactate, CRP, blood cultures x2, wound cultures at debridement, ABG, type & cross (IDSA 2014)
    inputs: wbc, sodium, creatinine, crp, hemoglobin, glucose
    actions: panel.cbc, panel.renal, panel.inflammation, workup.cellulitis_necfasc
    advance: labs drawn + cultures obtained pre-antibiotics
  6. 6BRANCHING_WORKUP
    CT with contrast for gas / fascial fluid; MRI if CT equivocal (do not delay surgery for imaging if high clinical suspicion); finger test / surgical exploration is GOLD STANDARD (IDSA 2014)
    advance: surgical exploration decision made
  7. 7DIFFERENTIAL
    NSTI Type I (polymicrobial, DM/postop) vs Type II (Group A Strep / S. aureus) vs Type III (Vibrio / Aeromonas — water) vs Type IV (fungal — immunocompromised); also: pyomyositis, severe cellulitis, gas gangrene (clostridial myonecrosis) (IDSA 2014)
    advance: NSTI type assigned
  8. 8RISK_STRATIFICATION
    LRINEC score (supportive only — never use to rule out); SIRS/qSOFA / SOFA for sepsis; mortality risk per organ failures (Wong 2004 PMID 15241098)
    inputs: wbc, sodium, creatinine, crp, hemoglobin, glucose
    actions: calc.qsofa, calc.sofa
    advance: LRINEC documented + sepsis stage assigned
  9. 9TREATMENT
    STAT surgical debridement (definitive — within hours of suspicion); empiric vancomycin + piperacillin-tazobactam + clindamycin (toxin suppression Eagle effect) within 1h; ICU resuscitation; serial OR returns q12-24h until viable tissue (IDSA 2014)
    inputs: creatinine, sbp
    advance: OR within hours + 3-drug empiric started
  10. 10DISPOSITION
    ICU for all confirmed NSTI; OR for STAT debridement; second-look at 12-24h (IDSA 2014)
    inputs: sbp
    advance: ICU + OR pathway locked
  11. 11MONITORING
    Serial debridements q12-24h until viable; vanc trough; lactate clearance; CK if myonecrosis; daily blood cultures until negative; de-escalate by culture (IDSA 2014)
    inputs: creatinine, lactate, wbc
    actions: panel.cbc
    advance: cultures speciated + antibiotics de-escalated + source controlled
  12. 12FOLLOWUP
    Wound care, skin grafting / reconstruction planning, PT/OT, prosthetics if amputation, infectious disease follow-up; total antibiotic course 2-4 weeks depending on source control (IDSA 2014)
    advance: discharge plan + reconstruction scheduled