12-phase flow (12)

1. 1FRAME
   Frame the preterm-NICU NEC presentation: gestational age + birth weight + chronologic age in days + onset relative to feeding-advance. Onset < day 7 + no pneumatosis + recent indomethacin/steroids → SIP suspicion (pivot to differential); onset week 2-4 in VLBW preterm post-feeding-advance → classic NEC pretest 7-10%; onset in term/late-preterm → atypical, broaden DDx (malrotation/volvulus, CHD with mesenteric ischemia, sepsis with translocation).
   inputs: gestational_age_weeks, birth_weight_grams, chronologic_age_in_days
   advance: NEC vs SIP vs broader-DDx framing set; gestational-age cohort tagged
2. 2ENTRY
   Recognise via clinical features (feeding intolerance + abdominal distention + occult/bloody stools) OR imaging (pneumatosis intestinalis, pneumoperitoneum, portal venous gas) OR lab (thrombocytopenia + metabolic acidosis). Stage I-IIA Bell features anchor entry; stage IIIB pneumoperitoneum is immediate surgical-emergency entry.
   inputs: feeding_status_and_advance_history, stool_occult_blood_or_visible_blood
   advance: NEC suspected by Bell-stage feature combination
3. 3CONTEXT
   Gestational age + birth weight + feeding status (mother's-own-milk vs donor-human-milk vs formula; recent advance) + indomethacin/steroid history (raises SIP differential) + central line / TPN duration (candidemia risk) + prior antibiotic exposure (Cantey 2018 dose-response).
   inputs: gestational_age_weeks, birth_weight_grams, feeding_status_and_advance_history, indomethacin_or_steroid_recent_exposure, central_line_or_tpn_duration, prior_antibiotic_exposure_days
   advance: Risk-factor profile + feeding context + medication history captured
4. 4RED_FLAGS
   Pneumoperitoneum on KUB (Stage IIIB — surgical emergency) → immediate pediatric surgery consult; hemodynamic instability (SBP < gestational-age threshold, lactate ≥ 5, vasoactive medication, capillary refill > 3 s, mottling) → ICU + max support; respiratory failure / apnoea + bradycardia (Stage IIIA features) → intubation + ventilator; bulging abdomen + fixed loop + abdominal-wall erythema + induration → advanced NEC (Stage IIB-III).
   inputs: temperature, sbp_neonate, spo2_neonate
   actions: protocol.septic_shock
   advance: Red flags actioned; surgical / ICU escalation within minutes if Stage IIIB
5. 5INITIAL_WORKUP
   NPO + NG decompression + IV access + bowel rest; CBC with diff (age-adjusted), CRP, blood culture (≥ 1 mL), metabolic panel, ABG/VBG, lactate, platelets, coag panel, stool occult / visible blood; KUB AP + left-lateral-decubitus views (pneumatosis, pneumoperitoneum, portal venous gas, fixed loop); empiric antibiotics within 1 h: Stage I-II → ampicillin + gentamicin (Gram-positive + Gram-negative + anaerobe baseline) OR pip-tazo; Stage III → pip-tazo OR meropenem + vancomycin (broader gram-negative + MRSA cover); + micafungin / L-AmB if Candida risk factors.
   inputs: cbc_with_diff_neonate, blood_culture, crp, metabolic_panel_neonate, lactate_neonate, platelets_neonate, coag_panel_neonate, abg_or_vbg_neonate, stool_occult_blood_or_visible_blood, kub_xray_serial
   actions: panel.cbc, panel.renal, panel.coag, panel.inflammation, panel.abg
   advance: NPO + NG; cultures sent; empiric antibiotics in; KUB obtained + Bell-staged
6. 6BRANCHING_WORKUP
   Source-directed: abdominal US for free fluid + bowel-wall thickening + portal venous gas (complementary to KUB); fungal cultures + 1,3-β-D-glucan if Candida risk (TPN + broad-abx + preterm + thrombocytopenia); CRBSI workup if central line — differential time-to-positivity (Mermel IDSA 2009); LP if sepsis coinfection with CNS features; serial KUB q6-12h for Bell-stage progression detection. SIP differential workup if onset < day 7 + no pneumatosis + recent indomethacin/steroids.
   inputs: abdominal_ultrasound, fungal_culture_or_beta_d_glucan
   actions: workup.crbsi, workup.bacterial_meningitis
   advance: Source identified or empirically covered; serial imaging plan in place
7. 7DIFFERENTIAL
   Spontaneous intestinal perforation (SIP) — early < day 7 + no pneumatosis + indomethacin/steroid exposure (Gordon 2007 pivot). NEC in term infant → broader DDx (malrotation/volvulus → upper GI series; congenital heart disease with mesenteric ischemia → echo; sepsis with bacterial translocation). Hirschsprung-associated enterocolitis (history of delayed meconium passage). Allergic enterocolitis (milk-protein-induced). Volvulus / intussusception (late-preterm and term). Coexistence pairs: NEC + sepsis (most cases); NEC + AKI; NEC + DIC; NEC + Candidemia.
   advance: Mimics excluded or co-managed; SIP-vs-NEC pivot resolved if early-onset
8. 8RISK_STRATIFICATION
   Bell modified staging (Walsh & Kliegman 1986): Stage I (suspected) → 48-72 h rule-out medical; Stage IIA (pneumatosis) → confirmed NEC + full 7-10 d course; Stage IIB (pneumatosis + acidosis + thrombocytopenia) → severe systemic involvement; Stage IIIA (advanced no-perforation; ventilator + hypotension + DIC + neutropenia) → ICU + max support + surgical readiness; Stage IIIB (pneumoperitoneum) → surgical emergency. Mortality: Stage I-IIA ~ 5%; Stage IIB ~ 15%; Stage III ~ 30-50%.
   inputs: kub_xray_serial, platelets_neonate, abg_or_vbg_neonate, sbp_neonate
   advance: Bell stage assigned + mortality stratified + surgical-vs-medical pathway chosen
9. 9TREATMENT
   Medical management for Stage I-II: NPO 7-14 d + NG decompression + IV crystalloid maintenance + TPN + central venous access + bowel rest; antibiotics 7-10 d (Stage I-II) — ampicillin + gentamicin OR pip-tazo OR meropenem (broader); + acyclovir if HSV features ≤ 28 d; + micafungin / L-AmB if Candida risk. Surgical management for Stage IIIB: pediatric surgery consult; peritoneal drain (extremely preterm < 1000 g, unstable) vs laparotomy (larger / definitive); resection of necrotic bowel ± ostomy formation. Antibiotic course 10-14 d for Stage III. Vasoactive — epinephrine 0.05-0.3 µg/kg/min OR dopamine 5-15 µg/kg/min OR norepinephrine 0.05-0.5 µg/kg/min; hydrocortisone 1 mg/kg q8h if catecholamine-resistant.
   inputs: birth_weight_grams, gestational_age_weeks, sbp_neonate, kub_xray_serial
   actions: protocol.septic_shock
   advance: NPO + NG + antibiotics + fluid/TPN + surgical-vs-medical plan in place; vasoactive titrated if shock
10. 10DISPOSITION
    NICU for all NEC (Stage I-III); pediatric surgical service for Stage IIIB or rapidly deteriorating Stage IIIA; step-down to level-2 special care nursery only after antibiotic course complete + tolerating feed advances + Bell-staging resolved. PICU rare (most centres NICU-manages all neonates).
    inputs: sbp_neonate, spo2_neonate
    advance: Level of care set; surgical service involved if Stage IIIB
11. 11MONITORING
    Vitals q4h (q1h initially in ill neonate), abdominal girth q4h, NG output + stool output + emesis q4h, weight daily, lactate trend q2-4h until normalised, CBC + CRP + platelets at 24 + 48 h, blood culture follow-up at 24 + 48 h, vancomycin / gentamicin levels per pharmacy (trough or AUC), serial KUB q6-12h during acute phase, daily reassessment of antibiotic + duration with goal de-escalation per Cantey 2018 stewardship; nutrition + feeding-advance plan; developmental + feeding follow-up.
    inputs: cbc_with_diff_neonate, crp, blood_culture, platelets_neonate, kub_xray_serial
    actions: panel.cbc, panel.renal, panel.inflammation
    advance: Response confirmed; antibiotics narrowed or completed; KUB resolution; tolerating feed advances
12. 12FOLLOWUP
    Outpatient peds within 24-48 h of discharge for high-risk; 1-week visit for all; growth + feeding tracking + developmental milestones; peds-GI surveillance for stricture (~ 10-30% after Stage II-III medical; symptoms — feeding intolerance, distention, emesis post-recovery; contrast study + surgical resection if symptomatic stricture); peds-surgery follow-up for post-op (ostomy management, takedown timing); nutrition follow-up for SBS / IFALD if extensive resection (TPN management, lipid strategy, central line care, intestinal transplant evaluation if non-rehabilitatable); neurodevelopmental peds at 6 + 12 + 24 mo (Bayley III / ASQ-3 — preterm + NEC survivors at elevated risk); immunization catch-up per cause (PCV / Hib + hepatitis B); hearing screen if meningitis precipitant. Family education on return precautions; vaccination of family contacts (Tdap, influenza, COVID-19); breastfeeding support.
    advance: Outpatient plan documented; peds-GI + peds-surgery + nutrition + neurodev follow-up scheduled; family education delivered