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surgery.necrotizing-soft-tissue-infection.core.v1PRODUCTION
surgery.necrotizing-soft-tissue-infection.core.v1

Necrotizing Soft-Tissue Infection

infectious_diseaseacuteadult
Hard-required inputs
0 / 8
Care setting:

Encounter flow

12/12 authored

Canonical 12-phase frame with authored status for this dossier.

Current phase

Frame

Detailed

Confirm NSTI suspicion; distinguish from severe non-necrotizing cellulitis / abscess (IDSA 2014)

Inputs
2
Actions
0
Advance rule
Set
Advance when

NSTI in differential

Patient inputs (15)

Mortality + drug-clearance considerations (IDSA 2014)

Fever > or = 38 or hypothermia in shock (IDSA 2014)

Tachycardia + hypotension = sepsis screen (IDSA 2014)

WBC >15 contributes to LRINEC; sepsis-3 component (Wong 2004 PMID 15241098)

Hyponatremia <135 in LRINEC; common in NSTI from third-spacing (Wong 2004)

AKI from sepsis + antibiotic dosing (vanc trough, pip-tazo) (IDSA 2014)

CRP >150 = 4 LRINEC points; inflammation marker (Wong 2004 PMID 15241098)

Septic shock (toxin-mediated streptococcal TSS) drives ICU + IVIG consideration (IDSA 2014)

Major risk factor for NSTI; alters empiric coverage (IDSA 2014)

Cirrhosis / CKD / cancer / steroids / IVDU drive empiric breadth (IDSA 2014)

Vibrio vulnificus exposure -> add doxycycline + ceftriaxone (IDSA 2014)

Portal of entry / postoperative wound infection (IDSA 2014)

Anemia / hemolysis contributes to LRINEC (Wong 2004)

Hyperglycemia >180 in LRINEC; diabetic risk factor (Wong 2004)

Sepsis severity; hypoperfusion marker (IDSA 2014)

* = hard-required. Engine cannot meaningfully run until these are filled.

Severity triggers (5)

5 need judgement
  • informationallife_threateningstreptococcal_toxic_shock_refractory
    Group A Strep NSTI + hypotension + multi-organ failure (BP <90, Cr >2, LFTs >2x, coagulopathy, ARDS, rash) — Streptococcal TSS criteria (IDSA 2014)
    Trigger could not be auto-evaluated — needs clinician judgement.
  • informationallife_threateningclostridial_myonecrosis_gas_gangrene
    Crepitus + dishwater drainage + rapid progression + soft tissue gas on imaging — clostridial myonecrosis (IDSA 2014)
    Trigger could not be auto-evaluated — needs clinician judgement.
  • informationallife_threateningfournier_gangrene_perineal
    Perineal / scrotal NSTI; rapid progression; urology + GS + plastics coordination (IDSA 2014)
    Trigger could not be auto-evaluated — needs clinician judgement.
  • informationallife_threateningvibrio_aeromonas_water_exposure
    NSTI + recent saltwater / brackish exposure / shellfish ingestion + cirrhosis -> Vibrio vulnificus; freshwater wound -> Aeromonas (IDSA 2014)
    Trigger could not be auto-evaluated — needs clinician judgement.
  • informationalseverelrinec_high_risk
    LRINEC score >=8 (high risk >75% probability NSTI) (Wong 2004 PMID 15241098)
    Trigger could not be auto-evaluated — needs clinician judgement.

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RED_FLAGSrequiredDrives severity classification
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Recommended regimen

NSTI — empiric broad-spectrum antibiotics + surgical source control (IDSA 2014)
axis: nsti_empiric_pathwaystep 1 - Step 1 — Empiric broad-spectrum antibiotics within 1 hour (after cultures)
Selected step "Step 1 — Empiric broad-spectrum antibiotics within 1 hour (after cultures)" — NSTI suspected on clinical grounds (do NOT wait for imaging or LRINEC)
  • vancomycin
    first line
    glycopeptide_MRSA
    25-30 mg/kg IV loading then 15-20 mg/kg q8-12h (target AUC 400-600 or trough 15-20) • IV • q8-12h
    triggers: NSTI_empiric, MRSA_coverage_needed
    MRSA coverage (Class I IDSA 2014); pair with pip-tazo + clinda for full empiric (PMID 24973422)
    rxcui 11124
  • piperacillin_tazobactam
    first line
    BL_BLI_anti_pseudomonal
    4.5 g IV q6h (or 3.375 g q6h; extended-infusion 4h preferred in severe sepsis) • IV • q6h
    triggers: NSTI_empiric, gram_neg_anaerobic_coverage
    Broad gram-neg + anaerobic + Pseudomonas (Class I IDSA 2014 PMID 24973422)
    rxcui 74169
  • clindamycin
    first line
    lincosamide_toxin_suppressor
    900 mg IV q8h • IV • q8h
    triggers: NSTI_empiric, streptococcal_toxin_suppression, eagle_effect
    Suppresses Group A Strep toxin (Eagle effect — works at high inoculum where beta-lactams fail); Class I IDSA 2014 for NSTI / strep TSS (PMID 24973422)
    rxcui 2582
  • meropenem
    contraindication substitute
    carbapenem
    1 g IV q8h • IV • q8h
    triggers: pip_tazo_allergy, ESBL_risk, severe_sepsis_empiric_broaden
    Alternative to pip-tazo when penicillin allergy / ESBL risk; pair with vanc + clinda (IDSA 2014)
    rxcui 29561
  • linezolid
    contraindication substitute
    oxazolidinone_MRSA
    600 mg IV q12h • IV • q12h
    triggers: vancomycin_intolerance, vancomycin_resistance, AKI
    Alternative MRSA agent when vanc contraindicated; suppresses staph toxin (similar to clinda); IDSA 2014 (PMID 24973422)
    rxcui 190376
  • daptomycin
    contraindication substitute
    lipopeptide_MRSA
    6-8 mg/kg IV daily (NOT for lung infection) • IV • daily
    triggers: vancomycin_intolerance, soft_tissue_MRSA_no_pulmonary_involvement
    Alternative MRSA agent for soft tissue when vanc fails / not tolerated (IDSA 2014); inactivated by surfactant — no pulmonary coverage
    rxcui 22299

ed playbook — drug actions (5)

  1. 1. crystalloid resuscitation
    30 mL/kg IV LR or NS over 3h • IV • bolus then maintenance
    trigger: Sepsis / septic shock (Surviving Sepsis 2021)
    Sepsis bundle (IDSA 2014)
  2. 2. vancomycin
    25-30 mg/kg IV loading • IV • load then q8-12h
    trigger: NSTI empiric (after cultures) (IDSA 2014)
    MRSA coverage (PMID 24973422)
  3. 3. piperacillin-tazobactam
    4.5 g IV q6h • IV • q6h
    trigger: NSTI empiric (after cultures) (IDSA 2014)
    Gram-neg + anaerobic + Pseudomonas (PMID 24973422)
  4. 4. clindamycin
    900 mg IV q8h • IV • q8h
    trigger: NSTI empiric (toxin suppression) (IDSA 2014)
    Eagle effect — toxin suppression in Group A Strep / clostridial (PMID 24973422)
  5. 5. norepinephrine
    0.05-0.5 mcg/kg/min titrated • IV • continuous
    trigger: MAP <65 despite 30 mL/kg fluid (Surviving Sepsis 2021)
    Septic shock vasopressor first-line

Auto-drafted A&P note

ed

Subjective

- Possible entry pathways: Pain out of proportion to exam findings (hallmark) (IDSA 2014); Cellulitis with rapid spread, systemic toxicity, hemorrhagic bullae (IDSA 2014); Crepitus / gas in soft tissue / dishwater discharge from incision (IDSA 2014).

Objective

- No vitals, labs, or imaging entered for this encounter.

Assessment

**Necrotizing Soft-Tissue Infection** (surgery.necrotizing-soft-tissue-infection.core.v1).
Phenotype framing: 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)
Scope: Confirm NSTI suspicion; distinguish from severe non-necrotizing cellulitis / abscess (IDSA 2014)

No severity triggers fired against current inputs.

Plan

Regimen axis: **NSTI — empiric broad-spectrum antibiotics + surgical source control (IDSA 2014)** — step "Step 1 — Empiric broad-spectrum antibiotics within 1 hour (after cultures)".
1. vancomycin 25-30 mg/kg IV loading then 15-20 mg/kg q8-12h (target AUC 400-600 or trough 15-20) IV q8-12h (glycopeptide_MRSA, first line) — MRSA coverage (Class I IDSA 2014); pair with pip-tazo + clinda for full empiric (PMID 24973422)
2. piperacillin_tazobactam 4.5 g IV q6h (or 3.375 g q6h; extended-infusion 4h preferred in severe sepsis) IV q6h (BL_BLI_anti_pseudomonal, first line) — Broad gram-neg + anaerobic + Pseudomonas (Class I IDSA 2014 PMID 24973422)
3. clindamycin 900 mg IV q8h IV q8h (lincosamide_toxin_suppressor, first line) — Suppresses Group A Strep toxin (Eagle effect — works at high inoculum where beta-lactams fail); Class I IDSA 2014 for NSTI / strep TSS (PMID 24973422)
4. meropenem 1 g IV q8h IV q8h (carbapenem, contraindication substitute) — Alternative to pip-tazo when penicillin allergy / ESBL risk; pair with vanc + clinda (IDSA 2014)
5. linezolid 600 mg IV q12h IV q12h (oxazolidinone_MRSA, contraindication substitute) — Alternative MRSA agent when vanc contraindicated; suppresses staph toxin (similar to clinda); IDSA 2014 (PMID 24973422)
6. daptomycin 6-8 mg/kg IV daily (NOT for lung infection) IV daily (lipopeptide_MRSA, contraindication substitute) — Alternative MRSA agent for soft tissue when vanc fails / not tolerated (IDSA 2014); inactivated by surfactant — no pulmonary coverage

Setting playbook (ed) — Recognize NSTI, draw cultures, start empiric vanc + zosyn + clindamycin within 1h, resuscitate, expedite OR consultation, do NOT delay surgery for imaging (IDSA 2014)
7. crystalloid resuscitation 30 mL/kg IV LR or NS over 3h IV bolus then maintenance — Sepsis / septic shock (Surviving Sepsis 2021) (Sepsis bundle (IDSA 2014))
8. vancomycin 25-30 mg/kg IV loading IV load then q8-12h — NSTI empiric (after cultures) (IDSA 2014) (MRSA coverage (PMID 24973422))
9. piperacillin-tazobactam 4.5 g IV q6h IV q6h — NSTI empiric (after cultures) (IDSA 2014) (Gram-neg + anaerobic + Pseudomonas (PMID 24973422))
10. clindamycin 900 mg IV q8h IV q8h — NSTI empiric (toxin suppression) (IDSA 2014) (Eagle effect — toxin suppression in Group A Strep / clostridial (PMID 24973422))
11. norepinephrine 0.05-0.5 mcg/kg/min titrated IV continuous — MAP <65 despite 30 mL/kg fluid (Surviving Sepsis 2021) (Septic shock vasopressor first-line)

Non-pharmacologic actions:
- NPO immediately (IDSA 2014)
- IV access x 2 (large bore) (IDSA 2014)
- Foley for UOP monitoring (IDSA 2014)
- STAT surgical consult — fasciotomy / debridement is DEFINITIVE (IDSA 2014)
- Mark wound margins with sharpie + serial photos for progression (IDSA 2014)
- Tetanus prophylaxis if not current (IDSA 2014)
- Consider IVIG for streptococcal TSS with refractory shock (IDSA 2014)

AVOID / contraindication checks:
- Do_not_delay_OR_for_imaging_in_clear_NSTI (IDSA 2014)
- Always_pair_clindamycin_with_penicillin_G_in_GAS_TSS (IDSA 2014)
- Daptomycin_not_for_pulmonary_infection (IDSA 2014)
- Linezolid_avoid_with_SSRI_serotonin_syndrome_risk (IDSA 2014)
- Vanc_AUC_target_400_to_600_avoid_AKI (IDSA 2014)

Monitoring

Regimen monitoring:
- lactate clearance q2 to 4h in shock (IDSA 2014)
- vancomycin AUC or trough q24h during titration (IDSA 2014)
- daily CBC BMP LFTs CK during active NSTI (IDSA 2014)
- serial blood cultures until negative (IDSA 2014)
- serial OR returns q12 to 24h until viable tissue (IDSA 2014)
- duration typically 2 to 4 weeks total antibiotics post definitive source control (IDSA 2014)

Setting (ed) monitoring:
- Continuous vitals + telemetry (IDSA 2014)
- Lactate q2-4h (IDSA 2014)
- UOP hourly in shock (IDSA 2014)
- Wound margin progression q1-2h (IDSA 2014)

Follow-up plan: 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)
- Close-out criterion: discharge plan + reconstruction scheduled

Monitoring phase: Serial debridements q12-24h until viable; vanc trough; lactate clearance; CK if myonecrosis; daily blood cultures until negative; de-escalate by culture (IDSA 2014)

Disposition

Current setting: ed — Recognize NSTI, draw cultures, start empiric vanc + zosyn + clindamycin within 1h, resuscitate, expedite OR consultation, do NOT delay surgery for imaging (IDSA 2014)

Disposition criteria:
- OR emergent (within hours of suspicion) -> definitive debridement (IDSA 2014)
- ICU post-op for ALL confirmed NSTI (IDSA 2014)
- Wards never appropriate for active NSTI (IDSA 2014)

Escalation triggers (move to higher acuity):
- Septic shock -> ICU + vasopressors (IDSA 2014)
- Confirmed NSTI clinically/imaging -> STAT OR within hours (IDSA 2014)
- Refractory shock with TSS -> consider IVIG (IDSA 2014)
- Compartment involvement -> fasciotomy at debridement (IDSA 2014)

Earlier-Return Triggers

Return-precaution thresholds (watch for):
- [LIFE_THREATENING] Group A Strep NSTI + hypotension + multi-organ failure (BP <90, Cr >2, LFTs >2x, coagulopathy, ARDS, rash) — Streptococcal TSS criteria (IDSA 2014)
- [LIFE_THREATENING] Crepitus + dishwater drainage + rapid progression + soft tissue gas on imaging — clostridial myonecrosis (IDSA 2014)
- [LIFE_THREATENING] Perineal / scrotal NSTI; rapid progression; urology + GS + plastics coordination (IDSA 2014)

Citations

- IDSA 2014 Practice Guidelines for the Diagnosis and Management of Skin and Soft Tissue Infections (Stevens) — covers necrotizing infections, gas gangrene, Fournier, Vibrio [PMID:24973422](https://pubmed.ncbi.nlm.nih.gov/24973422/)
- Cited evidence (PMID 15241098) [PMID:15241098](https://pubmed.ncbi.nlm.nih.gov/15241098/)

Last reconciled with current guidelines: 2026-05-26.
References
  • IDSA 2014 Practice Guidelines for the Diagnosis and Management of Skin and Soft Tissue Infections (Stevens) — covers necrotizing infections, gas gangrene, Fournier, Vibrio — PMID:24973422
  • Cited evidence (PMID 15241098) — PMID:15241098