12-phase flow (12)

1. 1FRAME
   Frame around the ORBITAL SEPTUM: preseptal (Chandler I — eyelid only, no proptosis/EOM/acuity change) vs orbital/postseptal (Chandler II-V — the emergency). Orbital cellulitis is overwhelmingly secondary to ethmoid sinusitis and is pediatric-predominant. Source-sinusitis, cavernous-sinus-thrombosis, meningitis, sepsis, ROCM, and the optic-nerve arm are recognised and routed OUT by engine_id, not re-authored here (Chandler Laryngoscope 1970 PMID 5470225; Sansa-Perna 2020 PMID 32389323).
   advance: septum-based scope confirmed; not-this-engine concerns routed by engine_id
2. 2ENTRY
   Recognise the entry: periorbital swelling WITH proptosis/EOM restriction/chemosis (postseptal) vs eyelid swelling with normal acuity/motility/globe position (preseptal candidate) vs sinusitis-with-new-eye-signs vs immunocompromised-with-orbital-signs (ROCM screen). Record proptosis up front — the single cardinal preseptal/postseptal discriminator (Moreddu 2025 — clinical exophthalmos OR 25.0).
   inputs: proptosis
   actions: workup.acute_red_eye
   advance: entry trigger present; proptosis status recorded
3. 3CONTEXT
   Build the postseptal prior: painful/restricted EOM, chemosis, ethmoid-sinusitis source, age (Garcia-Harris decision axis, pediatric predominance), fever, recent sinus/dental/ocular surgery or trauma. Screen the ROCM substrate (diabetes/DKA, neutropenia, transplant). This phase assigns the preseptal-vs-postseptal pretest probability and Chandler stage.
   inputs: ophthalmoplegia_pain_on_eye_movement, chemosis, sinusitis_source, age, temperature, recent_sinus_dental_ocular_surgery_or_trauma
   actions: workup.acute_red_eye
   advance: Chandler stage + preseptal/postseptal pretest prior assigned
4. 4RED_FLAGS
   Optic-nerve compromise (acuity/colour drop, RAPD) → vision-threatening emergency, route to ophtho.acute-vision-loss.core.v1 + emergent decompression. Bilateral signs / multiple cranial neuropathies / fixed pupil → cavernous sinus thrombosis (Chandler V) → route to neuro.cavernous-sinus-thrombosis.core.v1. Meningismus / altered mental status → intracranial extension → route to neuro.bacterial-meningitis.core.v1. qSOFA≥2 / hypotension → id.sepsis.core.v1. Black necrotic eschar / rapid CN march in DKA/immunocompromise → ROCM → route to id.invasive-fungal-sinusitis.core.v1. These are recognised here, NOT managed here.
   inputs: visual_acuity_and_colour_vision, rapd_relative_afferent_pupillary_defect, bilateral_signs_or_cranial_neuropathy, sbp, immunocompromise_or_dka
   actions: workup.acute_vision_loss, calc.qsofa
   advance: vision / CST / intracranial / sepsis / ROCM red flags screened and routed by engine_id if positive
5. 5INITIAL_WORKUP
   Contrast CT orbits + paranasal sinuses is the decisive test — confirms postseptal disease, stages Chandler III-IV, measures subperiosteal-abscess volume, localises the source sinus and any intracranial extension (Le J AAPOS 2014 PMID 24924283; Todman & Enzer 2011 PMID 21415801). CBC + CRP baseline (CRP >60, WBC >15,600 predict surgical need — Moreddu 2025); blood cultures (low yield but obtained before antibiotics); creatinine for vancomycin/amphotericin dosing. Do NOT delay IV antibiotics for imaging.
   inputs: contrast_ct_orbits_and_sinuses, wbc, crp
   actions: panel.cbc, panel.inflammation, panel.cmp
   advance: contrast CT orbits+sinuses obtained (or initiated) + baseline labs sent + IV antibiotics started
6. 6BRANCHING_WORKUP
   Chandler-stage decision tree on CT: Stage II orbital cellulitis (no abscess) → IV antibiotics + close observation; Stage III subperiosteal abscess → Garcia-Harris age + SPA-volume-stratified medical-vs-surgical; Stage IV orbital abscess → surgical drainage; Stage V cavernous sinus thrombosis → route OUT. MRI / MRV if CST or intracranial extension suspected. If diabetic/immunocompromised: nasal endoscopy + biopsy for ROCM (do not await — route OUT). Differentiate the non-infective look-alikes (idiopathic orbital inflammation, thyroid eye disease, orbital tumour/rhabdomyosarcoma).
   inputs: contrast_ct_orbits_and_sinuses
   actions: workup.acute_vision_loss, workup.acute_red_eye
   advance: Chandler stage assigned on imaging; medical vs surgical branch selected; non-infective mimic excluded or routed
7. 7DIFFERENTIAL
   Terminal differential with named pivots: orbital (postseptal) cellulitis vs preseptal cellulitis (proptosis + painful EOM + acuity/RAPD pivot — the septum) vs idiopathic orbital inflammation/orbital pseudotumour (subacute, steroid-responsive, often no fever/leukocytosis pivot) vs thyroid eye disease (bilateral, lid retraction/lag, no fever, chronic pivot) vs orbital tumour/rhabdomyosarcoma (progressive painless mass, child, no infective markers pivot — biopsy) vs ROCM mucormycosis (DKA/immunocompromise + black eschar + rapid CN march pivot) vs cavernous sinus thrombosis (bilateral + CN III/IV/V1/VI pivot — route OUT)
   advance: single best diagnosis selected; mimic vs infective resolved; ROCM and CST explicitly excluded or routed
8. 8RISK_STRATIFICATION
   Chandler stage drives disposition (I outpatient-eligible → II-V admit). Layer the surgical-need predictors: clinical exophthalmos (OR 25.0), ophthalmoplegia (OR 14.2), CRP >60 (OR 6.9), WBC >15,600 (OR 7.7), SPA volume >3.8 mL (71% surgery), bony destruction, optic compromise (Moreddu J Otolaryngol HNS 2025 PMID 40652356; Le J AAPOS 2014 PMID 24924283). qSOFA/NEWS2 for systemic-toxicity escalation.
   inputs: temperature, sbp, crp, wbc
   actions: calc.qsofa, calc.news2
   advance: Chandler stage + surgical-need risk overlay assigned
9. 9TREATMENT
   Postseptal disease = inpatient IV broad-spectrum empiric covering MSSA/MRSA + streptococci (incl. S. anginosus group) + anaerobes: vancomycin + ceftriaxone (or ampicillin-sulbactam) ± metronidazole; clindamycin where anaerobe/penicillin issues (Cirks Mil Med 2025 PMID 39172646 — 25% MRSA, anaerobes; empiric clindamycin+ceftriaxone). Surgical-drainage decision (NON-pharmacologic): Chandler IV / large or non-medial SPA / age ≥9 / optic compromise / no 24-48 h improvement → endoscopic ± external orbital drainage + sinus surgery (Garcia & Harris Ophthalmology 2000 PMID 10919887; Le 2014). ROCM → lipid amphotericin B + EMERGENT surgical debridement + correct DKA/immunosuppression (route to fungal-sinusitis engine; recognised here). IV→PO step-down once afebrile + orbital signs regressing. Preseptal (Chandler I) → oral/ambulatory-IV antibiotics with daily review (Brugha Pediatr Emerg Care 2012 PMID 22344208).
   inputs: creatinine, pregnancy, age, sinusitis_source
   advance: IV empiric started for postseptal disease; surgical-drainage decision made; ophthalmology + ENT engaged; ROCM routed if present
10. 10DISPOSITION
    Chandler I preseptal, well, reliable, no orbital signs → ambulatory IV / oral with 24 h review (Brugha 2012 PMID 22344208). Chandler II-V → ADMIT, urgent ophthalmology + ENT co-management, IV antibiotics ± surgery. Optic compromise / CST / intracranial extension / ROCM / sepsis → admit + route OUT by engine_id to the owning engine with carryover state.
    inputs: proptosis, visual_acuity_and_colour_vision, sbp
    advance: disposition documented; admit + co-management for any postseptal disease; route-outs executed
11. 11MONITORING
    Serial visual acuity, colour vision, pupillary (RAPD), motility, and proptosis checks every 4 h (or more frequently if optic compromise) — deterioration mandates urgent re-imaging + surgical drainage (Garcia & Harris Ophthalmology 2000 — non-surgical SPA needs close observation). CRP/WBC trend; expect improvement within 24-48 h of correct IV therapy; failure to improve by 24-48 h triggers re-CT + surgical re-evaluation, NOT silent antibiotic continuation (Le J AAPOS 2014).
    inputs: visual_acuity_and_colour_vision, crp, wbc
    actions: panel.inflammation
    advance: objective orbital + inflammatory improvement by 24-48 h, OR surgical/re-imaging re-evaluation triggered
12. 12FOLLOWUP
    Complete IV→PO course (typically 2-3 weeks total guided by source-sinusitis and complication); ENT follow-up for the source ethmoid sinusitis and FESS planning (route to ent.acute-sinusitis.core.v1 for definitive sinus management); ophthalmology follow-up for residual diplopia / optic-nerve / motility sequelae; recurrence-driver control (treat the source sinus disease); ROCM survivors → prolonged antifungal + reconstruction. Counsel return precautions: any vision change, increasing proptosis, new diplopia, headache, or altered mental status → emergency return.
    inputs: sinusitis_source
    advance: antibiotic course + ENT/ophthalmology follow-up + source-sinus management plan documented; return precautions given