12-phase flow (12)

1. 1FRAME
   Confirm necrotising fasciitis / Fournier / gas gangrene scope per Stevens IDSA SSTI 2014 + WSES/SIS-E 2018 — surgical emergency; differentiate from severe cellulitis without NF (Stevens IDSA 2014; Wong 2003)
   advance: scope confirmed: cellulitis with cardinal NF features OR LRINEC ≥ 6 OR clinical suspicion meeting T_treat surgical
2. 2ENTRY
   Pain out of proportion to exam, rapidly extending erythema, hemorrhagic bullae, crepitus, anaesthesia, dishwater drainage, sepsis with skin source, OR inflow from id.cellulitis.core.v1 / id.sepsis.core.v1 (Stevens IDSA 2014)
   inputs: pain_out_of_proportion, rapid_extension_of_erythema
   advance: entry trigger validated
3. 3CONTEXT
   Capture site (extremity / Fournier / cervical / abdo wall / thoracic); host (DM / IC / IDU / Vibrio-exposure / trauma / surgical-site / varicella / pregnant / pediatric); pre-empiric Type (I/II/III/IV) from history; mark border with skin marker (Stevens IDSA 2014; WSES/SIS-E 2018)
   inputs: diabetes_mellitus, immunocompromised_host, salt_water_or_raw_oyster_exposure
   advance: phenotype matrix populated; empiric regimen selectable; surgical service activated
4. 4RED_FLAGS
   Cardinal NF signs — pain out of proportion (LR+ ≈5-8), hemorrhagic bullae (LR+ ≈10), crepitus (LR+ ≈9), anaesthesia (LR+ ≈12), rapid extension >1 cm/h, septic shock, STSS, LRINEC ≥ 6 (LR+ ≈10) (Wong 2003; Stevens IDSA 2014; WSES/SIS-E 2018)
   inputs: sbp, heart_rate, crepitus_or_hemorrhagic_bullae, anaesthesia_of_involved_skin
   actions: calc.qsofa
   advance: surgical activation made within 1 h of recognition; broad empirics + ICU disposition pre-set
5. 5INITIAL_WORKUP
   Bedside vitals + qSOFA, CBC + BMP + LFT + CRP + lactate + coagulation, ≥ 2 blood cultures before first abx (unless shock), wound culture if drainage, mark border with skin marker, ECG (Stevens IDSA 2014; WSES/SIS-E 2018; SSC 2026)
   inputs: wbc, hemoglobin, sodium, creatinine, glucose, crp, lactate, blood_cultures_2_sets
   actions: panel.cbc, panel.renal, panel.inflammation
   advance: baseline diagnostic set complete; LRINEC computed (with caveat that low score does NOT exclude); empirics started within 1 h
6. 6BRANCHING_WORKUP
   When clinical picture diagnostic: NO imaging — STAT OR. When clinical picture equivocal: plain film for gas (rapid bedside) OR bedside US OR CT (fascial gas / fluid / edema LR+ ≈8) OR MRI (LR+ ≈10; stable patient only). Bedside finger-test in OR is gold-standard diagnostic act (LR+ ≈50) (Stevens IDSA 2014; WSES/SIS-E 2018)
   advance: imaging deferred when clinically NF — STAT OR; imaging done only when picture equivocal AND patient stable
7. 7DIFFERENTIAL
   Distinguish NF from severe cellulitis (parent dossier), erysipelas, pyomyositis, compartment syndrome, deep abscess, gas gangrene without NF, TSS without NF, DVT mimicker, spider envenomation (Loxosceles), severe contact dermatitis (Stevens IDSA 2014; Wong 2003)
   advance: NF confirmed clinically or by finger-test in OR; alternative dx ruled out or routed
8. 8RISK_STRATIFICATION
   Stratify by Type (I/II/III/IV) + LRINEC tier + qSOFA / SOFA + organ-failure + site + shock state — drives surgery timing tier (< 6 h target), ICU disposition, IVIG / HBO consideration, second-look timing (Stevens IDSA 2014; WSES/SIS-E 2018; SSC 2026)
   inputs: sbp, heart_rate, lactate
   actions: calc.qsofa, calc.sofa
   advance: severity tier + surgical timing + ICU/IVIG/HBO decision made
9. 9TREATMENT
   EMERGENT OR within 6 h (target < 1 h from recognition; mortality doubles per 6 h delay); empiric broad-spectrum + toxin suppression: piperacillin-tazobactam + vancomycin + clindamycin within 1 h (Stevens IDSA 2014); add doxycycline + cefotaxime for Vibrio (Horseman 2011); penicillin G + clindamycin for clostridial; IVIG for STSS (Stevens IDSA 2014 Class IIa); liposomal AmB + isavuconazole for Type IV fungal; pathogen-targeted post-cultures (Stevens IDSA 2014)
   inputs: creatinine
   advance: empirics active within 1 h; surgical debridement within 6 h target; pathogen-targeted de-escalation at species + susceptibility
10. 10DISPOSITION
    ICU for shock / pre-shock / Fournier with diversion / large debridement / STSS; cardiothoracic / plastic / orthopaedic surgery activation for reconstructive planning; do NOT discharge from ED (Stevens IDSA 2014; WSES/SIS-E 2018)
    inputs: sbp
    advance: level of care set; multidisciplinary team activated (surgery + ICU + ID + plastic + microbiology)
11. 11MONITORING
    Mandatory second-look at 24-48 h (Stevens IDSA 2014); tertiary debridement if necrosis advancing; daily exam + dressing change + culture from each debridement; lactate / SOFA / vasopressor trend; AKI monitoring (vanco AUC, cefotaxime renal); clostridial → colon workup once stable for C. septicum (Stevens IDSA 2014; Rybak 2020)
    inputs: lactate, creatinine
    actions: panel.renal
    advance: wound stable + cultures cleared + hemodynamic stability + reconstructive plan
12. 12FOLLOWUP
    Physical / occupational rehab; plastic / reconstructive surgery for closure / grafting / amputation prosthesis; psychological sequelae after disfiguring debridement; OUD linkage if IDU; addiction medicine consult; diabetes optimisation; colon-cancer workup for C. septicum; community follow-up (Stevens IDSA 2014; AAP 2018)
    advance: rehab + reconstructive plan + OUD linkage (if IDU) + colon workup (if C. septicum) scheduled