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cardio.post-arrest.hypothermia.v1

Post-cardiac-arrest care — hypothermic cardiac arrest

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Phase E variant of cardio.post-arrest.core.v1 — narrowed to hypothermic cardiac arrest cohort. Bradycardia → asystole most common; VF possible. "Not dead until warm and dead" maxim drives extended ACLS until rewarmed to 32-35 °C. Severity stratification: mild 32-35 °C (passive warming), moderate 28-32 °C (active warming + drug spacing), severe <28 °C (ECMO/CPB candidate per ELSO + Walpoth 1997). Drug + defib modifications per AHA 2020 hypothermia §: epi withheld at core <30 °C, spaced q6-10 min at 30-34 °C; defib limited to 1 attempt at <30 °C. ECMO/CPB rewarming is gold standard for severe hypothermia + arrest; favourable outcomes documented at very low core temperatures (Walpoth 1997 PMID 9395428). Inherits manifest + design-brief pointer from parent. 5 setting playbooks (ed, icu, inpatient, transition, outpatient). 5 severity triggers: severe hypothermia <28 °C ECMO candidate, recurrent VF at low temp, refractory acidosis post-rewarming, rewarming vasoplegia, ECMO eligibility. Status INTEGRATED until terminology + RxNav-validated drug codes are reconciled. Authored 2026-05-15 by shard-06-cardio-acute Phase E wave 9.

Entry points (3)

  • symptom
    ROSC after hypothermic cardiac arrest — environmental, immersion, drug-induced, or endocrine etiology
    rosc_after_hypothermic_cardiac_arrest
  • vital_abnormality
    Severe accidental hypothermia (core <28 °C) with cardiac arrest — ECMO/CPB candidate per ELSO consensus
    severe_hypothermia_below_28c_with_arrest
  • history
    Comatose post-rewarming hypothermic arrest survivor — TTM candidate; neuroprog interpreted with caution given hypothermia confounding (Sandroni 2021 PMID 33745427)
    comatose_post_rewarming_with_unknown_neuro_status

Required inputs (20)

  • agerequired
    demographic • used at CONTEXT
    Elderly more vulnerable to hypothermia (lower thermoregulatory reserve, increased polypharmacy risk); pediatric thermoregulation patterns differ
  • exposure_mechanismrequired
    history • used at CONTEXT
    Environmental (alpine, winter exposure, homeless, cold-water immersion / drowning) vs drug-induced (alcohol, sedatives, opioids) vs endocrine (myxedema coma) — mechanism drives etiologic workup + rewarming pace
  • estimated_exposure_durationrequired
    history • used at CONTEXT
    Brief exposure with rapid cooling = better prognosis than prolonged exposure with slow cooling; modifies ECMO eligibility decision
  • arrest_witnessedrequired
    history • used at CONTEXT
    Witnessed + bystander CPR + low-flow time → favorable neuro prognosis (AHA 2020); CAHP/OHCA score inputs (note: hypothermia itself confers cerebral protection)
  • initial_rhythmrequired
    history • used at CONTEXT
    Bradycardia → asystole most common in deep hypothermia (slowed conduction); VF possible if electrolyte derangement or rapid temperature shift
  • low_flow_time_minrequired
    history • used at CONTEXT
    CPR duration → ECPR eligibility (ARREST PMID 33308475 — <60 min low-flow); cold-water hypothermia tolerates much longer downtime than normothermic arrest
  • co_existing_trauma_or_immersion
    history • used at CONTEXT
    Many hypothermic arrests co-occur with trauma (skiing, mountaineering) or drowning (cold-water immersion); modifies rewarming + workup
  • thyroid_or_adrenal_history
    history • used at CONTEXT
    Myxedema coma + adrenal crisis can present as hypothermic arrest; check TSH + cortisol if endocrine etiology suspected
  • sbprequired
    vital • used at TREATMENT
    Hypothermia produces transient bradycardia + hypotension that often improves with warming; MAP ≥65 target post-ROSC; rewarming-related vasoplegia common
  • core_temprequired
    vital • used at CONTEXT
    Severity stratification: mild 32-35 °C (passive warming sufficient); moderate 28-32 °C (active warming + drug spacing); severe <28 °C (ECMO/CPB candidate); measure with esophageal / bladder / rectal probe (low-reading thermometer)
  • spo2required
    vital • used at TREATMENT
    Avoid hyperoxia: SpO2 92-98% (AHA 2020 Class IIa); severe hypothermia produces left-shifted oxyhemoglobin curve
  • ecg_12_leadrequired
    imaging • used at INITIAL_WORKUP
    Osborn (J) waves at QRS-ST junction at core <30 °C — classic; prolonged PR/QRS/QTc; bradycardia; AF common; rule out underlying ischemic / channelopathy trigger
  • troponinrequired
    lab • used at INITIAL_WORKUP
    Cardiac etiology workup if ischemic precipitant suspected; rises from prolonged hypoperfusion + arrest itself
  • lactaterequired
    lab • used at INITIAL_WORKUP
    Tissue hypoperfusion; rises with rewarming as peripheral perfusion restored ("rewarming acidosis"); clearance trajectory drives prognosis (SCAI 2022 PMID 35718438)
  • creatininerequired
    lab • used at CONTEXT
    AKI common post-arrest + rhabdo from prolonged immobility; drug renal-adjustment
  • potassiumrequired
    lab • used at INITIAL_WORKUP
    Hyperkalemia from cell lysis + acidosis; K >12 mmol/L = traditional poor-prognosis marker per ELSO + Brown 2012 PMID 23215559 (relative cutoff in ECMO selection)
  • tsh_and_cortisol_if_myxedema_suspected
    lab • used at INITIAL_WORKUP
    Myxedema coma + adrenal crisis can present as hypothermic arrest; empiric stress-dose steroids + thyroid hormone if suspected before labs return
  • ethanol_and_drug_screen
    lab • used at INITIAL_WORKUP
    Toxicology common precipitant of hypothermia (alcohol, sedatives, opioids impair thermoregulation)
  • cxr_post_rewarmingrequired
    imaging • used at INITIAL_WORKUP
    Pulmonary edema common with rewarming; aspiration; pneumothorax from CPR; ARDS evolution
  • echo_post_rosc
    imaging • used at INITIAL_WORKUP
    LV/RV function for cardiac trigger workup; post-arrest dysfunction; rewarming-related changes

12-phase flow (12)

  1. 1FRAME
    Hypothermic cardiac arrest — bradycardia → asystole most common; VF possible; "not dead until warm and dead" maxim drives extended ACLS until rewarmed to 32-35 °C; ECMO/CPB gold standard for profound hypothermia + arrest; route to parent cardio.post-arrest.core.v1 for TTM + neuroprog
    inputs: core_temp, exposure_mechanism
    advance: hypothermic etiology + severity stratified by core temp
  2. 2ENTRY
    Modified ACLS: continuous compressions; intubate early; warm humidified ventilation; if core <30 °C withhold further epi/amiodarone doses + limit defib to 1 attempt; if 30-34 °C space drugs q6-10 min; activate ECMO/CPB team if severe hypothermia + arrest
    inputs: age, arrest_witnessed, core_temp, initial_rhythm
    advance: modified ACLS + active warming + ECMO team alerted (if indicated)
  3. 3CONTEXT
    Exposure mechanism + duration, witnessed status, low-flow time, drug/alcohol history, endocrine history, co-existing trauma or immersion
    inputs: estimated_exposure_duration, low_flow_time_min, co_existing_trauma_or_immersion, thyroid_or_adrenal_history, sbp, spo2, creatinine
    advance: context complete + GOC documented + family informed
  4. 4RED_FLAGS
    Severe hypothermia <28 °C with arrest (ECMO candidate); refractory VF/asystole at warm core temp; severe hyperkalemia >10-12 (traditional poor-prognosis marker); rewarming-related arrhythmias / vasoplegia / pulmonary edema; co-existing trauma
    inputs: core_temp, potassium, sbp
    actions: cardiogenic_shock
    advance: red flags screened + ECMO/CPB decision made + escalations triggered
  5. 5INITIAL_WORKUP
    ECG + serial troponin + BMP + lactate + ABG + CBC + coags + ETOH + UDS + TSH + cortisol (if myxedema suspected) + CXR + bedside echo + CT head if AMS or trauma; consider CT C-spine if trauma mechanism
    inputs: ecg_12_lead, troponin, lactate, potassium, cxr_post_rewarming
    actions: post_arrest_care, panel.cardiac, panel.renal
    advance: workup complete + endocrine + cardiac + co-injury assessed
  6. 6BRANCHING_WORKUP
    ECMO/CPB rewarming if severe hypothermia + arrest; STEMI on post-ROSC ECG → cath; recurrent VT/VF post-rewarming → EP / channelopathy workup; ARDS post-rewarming → ARDSnet vent; myxedema coma → IV levothyroxine + stress-dose steroids
    actions: acs_pathway, wide_complex_tach
    advance: rewarming method + cardiac vs endocrine vs trauma branching decided
  7. 7DIFFERENTIAL
    Primary environmental hypothermia vs drug-induced (alcohol, sedatives) vs endocrine (myxedema, adrenal crisis) vs sepsis-induced (cold sepsis in elderly) vs immersion / drowning vs trauma + exposure; co-precipitants common
    advance: primary mechanism + co-precipitants established
  8. 8RISK_STRATIFICATION
    Core temp + K + lactate + arrival pH + initial rhythm at 32 °C drive prognosis; CAHP/OHCA partial applicability (hypothermia confers cerebral protection); HOPE / ICE-PACS scores for ECMO selection in accidental hypothermia (Pasquier 2018 model); K >12 mmol/L traditional poor-prognosis cutoff
    inputs: core_temp, low_flow_time_min, sbp, lactate, potassium
    actions: calc.map, calc.heart, calc.ckd_epi_2021, calc.cha2ds2vasc
    advance: risk class + ECMO eligibility + continuation decision documented
  9. 9TREATMENT
    Active warming → ECMO/CPB if severe hypothermia + arrest (gold standard); less aggressive options if not ECMO candidate (warm IVF 40-42 °C, warm humidified vent, peritoneal/thoracic lavage, forced-air); standard post-ROSC bundle (vasopressor → MAP ≥65, lung-protective vent, sedation); TTM 33-37.5 °C × 24h after rewarming completed; etiology-specific therapy (IV levothyroxine + steroids if myxedema)
    inputs: sbp, core_temp, spo2, creatinine, potassium
    actions: protocol.cardiogenic_shock
    advance: rewarming + post-ROSC bundle + etiology-specific therapy delivered
  10. 10DISPOSITION
    CICU vs MICU per local pathway and predominant problem (cardiac etiology → CICU; environmental + multisystem → MICU); cardiology + intensivist + EP if channelopathy + endocrinology if myxedema
    advance: unit + service-line ownership assigned
  11. 11MONITORING
    Continuous telemetry + arterial line + central line + Foley; lactate q2-4h; BMP q6-12h; serial troponin; serial neuro exams; multimodal neuroprog ≥72h post-rewarm WITH CAUTION (Sandroni 2021 PMID 33745427) given hypothermia confounding biomarkers; continuous core temp monitoring during TTM
    inputs: creatinine, potassium
    actions: panel.renal, panel.cardiac
    advance: monitoring + neuroprog timeline documented with hypothermia caveat
  12. 12FOLLOWUP
    Cardiology + EP follow-up if cardiac trigger; endocrinology if myxedema or adrenal disease; substance-use referral if drug/alcohol precipitated; mental health (post-arrest PTSD high risk); social work (homelessness, exposure prevention); rehab for cognitive sequelae
    advance: cardiology + endo + substance-use + mental health + social work + rehab plan booked