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cardio.post-arrest.hypothermia.v1PRODUCTION
cardio.post-arrest.hypothermia.v1

Post-cardiac-arrest care — hypothermic cardiac arrest

cardiologyacuteadult
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12/12 authored

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

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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

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hypothermic etiology + severity stratified by core temp

Patient inputs (20)

Elderly more vulnerable to hypothermia (lower thermoregulatory reserve, increased polypharmacy risk); pediatric thermoregulation patterns differ

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

Brief exposure with rapid cooling = better prognosis than prolonged exposure with slow cooling; modifies ECMO eligibility decision

Witnessed + bystander CPR + low-flow time → favorable neuro prognosis (AHA 2020); CAHP/OHCA score inputs (note: hypothermia itself confers cerebral protection)

Bradycardia → asystole most common in deep hypothermia (slowed conduction); VF possible if electrolyte derangement or rapid temperature shift

CPR duration → ECPR eligibility (ARREST PMID 33308475 — <60 min low-flow); cold-water hypothermia tolerates much longer downtime than normothermic arrest

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)

AKI common post-arrest + rhabdo from prolonged immobility; drug renal-adjustment

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

Cardiac etiology workup if ischemic precipitant suspected; rises from prolonged hypoperfusion + arrest itself

Tissue hypoperfusion; rises with rewarming as peripheral perfusion restored ("rewarming acidosis"); clearance trajectory drives prognosis (SCAI 2022 PMID 35718438)

Hyperkalemia from cell lysis + acidosis; K >12 mmol/L = traditional poor-prognosis marker per ELSO + Brown 2012 PMID 23215559 (relative cutoff in ECMO selection)

Pulmonary edema common with rewarming; aspiration; pneumothorax from CPR; ARDS evolution

Hypothermia produces transient bradycardia + hypotension that often improves with warming; MAP ≥65 target post-ROSC; rewarming-related vasoplegia common

Avoid hyperoxia: SpO2 92-98% (AHA 2020 Class IIa); severe hypothermia produces left-shifted oxyhemoglobin curve

Many hypothermic arrests co-occur with trauma (skiing, mountaineering) or drowning (cold-water immersion); modifies rewarming + workup

Myxedema coma + adrenal crisis can present as hypothermic arrest; check TSH + cortisol if endocrine etiology suspected

Myxedema coma + adrenal crisis can present as hypothermic arrest; empiric stress-dose steroids + thyroid hormone if suspected before labs return

Toxicology common precipitant of hypothermia (alcohol, sedatives, opioids impair thermoregulation)

LV/RV function for cardiac trigger workup; post-arrest dysfunction; rewarming-related changes

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

Severity triggers (5)

5 need judgement
  • informationallife_threateningsevere_hypothermia_below_28c_with_arrest_ecmo_candidate
    Core temperature <28 °C with cardiac arrest — ECMO/CPB rewarming is gold standard (Walpoth 1997 PMID 9395428; ELSO accidental hypothermia consensus); favourable outcomes documented at very low core temperatures
    Trigger could not be auto-evaluated — needs clinician judgement.
  • informationallife_threateningrecurrent_vf_or_arrhythmia_at_low_core_temp
    Recurrent VF or arrhythmia at core temp <30 °C — drugs less effective, defibrillation limited; bridge with ECMO rewarming
    Trigger could not be auto-evaluated — needs clinician judgement.
  • informationallife_threateningecmo_eligibility_severe_hypothermia_with_arrest
    Severe hypothermia + cardiac arrest meeting ECMO criteria — witnessed event, no obvious lethal trauma, K typically <12 mmol/L (Brown 2012 + ELSO consensus); ECMO/CPB rewarming offers favourable outcomes even at very low temperatures
    Trigger could not be auto-evaluated — needs clinician judgement.
  • informationalsevererefractory_acidosis_post_rewarming
    Persistent severe metabolic acidosis (pH <7.2 + lactate >6) post-rewarming despite resuscitation — indicates inadequate perfusion or rewarming-related complication
    Trigger could not be auto-evaluated — needs clinician judgement.
  • informationalsevererewarming_related_vasoplegia_with_shock
    Profound vasoplegia + hypotension during rewarming — peripheral vasodilation as warming restores perfusion; common in moderate-to-severe hypothermia
    Trigger could not be auto-evaluated — needs clinician judgement.

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Recommended regimen

Hypothermic post-arrest phenotype — modified ACLS (drug spacing + defib limitation), ECMO/CPB rewarming gold standard for severe + arrest, etiology-specific endocrine therapy, post-rewarming bundle (AHA 2020 hypothermia + ERC 2021 + ELSO accidental hypothermia + Walpoth 1997)
axis: hypothermic_post_arrest_phenotype
Selected axis "Hypothermic post-arrest phenotype — modified ACLS (drug spacing + defib limitation), ECMO/CPB rewarming gold standard for severe + arrest, etiology-specific endocrine therapy, post-rewarming bundle (AHA 2020 hypothermia + ERC 2021 + ELSO accidental hypothermia + Walpoth 1997)" by default fallback (first axis)
  • norepinephrine
    first line
    vasopressor_alpha1_beta1
    0.05-0.5 µg/kg/min titrate MAP ≥65 • IV • continuous
    triggers: post_rosc_vasoplegia, rewarming_related_vasodilation_shock
    SOAP-II PMID 20200382; first-line post-ROSC vasoactive; particularly important during rewarming-related vasoplegia phase
    rxcui 7512
  • amiodarone
    first line
    class_iii_antiarrhythmic
    300 mg IV bolus → 150 mg if recurrent → 1 mg/min × 6h → 0.5 mg/min × 18h; HOLD additional doses if core <30 °C • IV • modified for hypothermia
    triggers: recurrent_vf_pvt_post_rewarming_above_30c
    AHA 2020 ACLS Class IIb; in hypothermia limit to 1 dose until warmed >30 °C, then resume standard cadence
    rxcui 703
  • epinephrine
    first line
    inotrope_chronotrope_vasopressor
    1 mg IV q3-5 min if normothermic; if core <30 °C → withhold further doses; if 30-34 °C → space q6-10 min • IV • modified for hypothermia
    triggers: cardiac_arrest_warm_core_temp, pea_asystole_at_or_above_30c
    AHA 2020 ACLS — modified dosing intervals for hypothermia given reduced metabolism + receptor responsiveness
    rxcui 3992
  • magnesium sulfate
    add on
    electrolyte_anti_arrhythmic
    1-2 g IV • IV • one-time + repeat for TdP
    triggers: torsades_de_pointes_post_rewarming, long_qt_unmasked
    AHA 2020 ACLS Class IIa for TdP; correct hypomagnesemia first
    rxcui 6585
  • levothyroxine
    comorbidity specific
    thyroid_hormone_replacement
    200-500 µg IV loading → 50-100 µg IV daily • IV • daily
    triggers: myxedema_coma_suspected_or_confirmed_with_hypothermic_arrest
    AACE myxedema coma management — IV levothyroxine + stress-dose steroids; precede T4 with hydrocortisone if adrenal insufficiency possible
    rxcui 10582
  • hydrocortisone
    comorbidity specific
    glucocorticoid_short_acting
    100 mg IV q8h × 24-48h • IV • q8h
    triggers: myxedema_coma, adrenal_crisis_suspected_with_hypothermic_arrest
    Standard adrenal crisis + myxedema coma management; precede levothyroxine with steroids to avoid precipitating crisis
    rxcui 5492
  • propofol
    first line
    sedative_iv_anesthetic
    5-50 µg/kg/min • IV • continuous; titrate RASS
    triggers: post_rosc_intubation_ttm
    PADIS 2018; hepatic metabolism slowed in hypothermia → reduce dose during cooling phase
    rxcui 8782
  • fentanyl
    first line
    opioid_analgesic
    25-200 µg/h • IV • continuous
    triggers: post_rosc_intubation_ttm, shivering_control
    PADIS 2018; analgesia + shivering suppression for TTM
    rxcui 4337
  • tranexamic acid
    add on
    antifibrinolytic
    1 g IV over 10 min • IV • within 3h of bleeding onset
    triggers: co_existing_trauma_with_bleeding
    CRASH-2 PMID 20554319 if traumatic bleeding co-existing with hypothermic arrest
    rxcui 10691

outpatient playbook — drug actions (3)

  1. 1. continue levothyroxine
    rxcui 6960
    levothyroxine titrated to TSH • PO • daily
    trigger: persistent hypothyroidism
    AACE thyroid
  2. 2. continue channelopathy regimen
    rxcui 6918
    nadolol or propranolol per type • PO • daily
    trigger: LQTS or CPVT
    HRS 2017
  3. 3. continue HF GDMT if structural CM
    rxcui 1656328
    sacubitril-valsartan + carvedilol + spironolactone + SGLT2i max tolerated • PO • as scheduled
    trigger: structural CM HFrEF
    ACC/AHA 2022 HF 4-pillar

Auto-drafted A&P note

outpatient

Subjective

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

Objective

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

Assessment

**Post-cardiac-arrest care — hypothermic cardiac arrest** (cardio.post-arrest.hypothermia.v1).
Phenotype framing: 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
Scope: 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

No severity triggers fired against current inputs.

Plan

Regimen axis: **Hypothermic post-arrest phenotype — modified ACLS (drug spacing + defib limitation), ECMO/CPB rewarming gold standard for severe + arrest, etiology-specific endocrine therapy, post-rewarming bundle (AHA 2020 hypothermia + ERC 2021 + ELSO accidental hypothermia + Walpoth 1997)**.
1. norepinephrine 0.05-0.5 µg/kg/min titrate MAP ≥65 IV continuous (vasopressor_alpha1_beta1, first line) — SOAP-II PMID 20200382; first-line post-ROSC vasoactive; particularly important during rewarming-related vasoplegia phase
2. amiodarone 300 mg IV bolus → 150 mg if recurrent → 1 mg/min × 6h → 0.5 mg/min × 18h; HOLD additional doses if core <30 °C IV modified for hypothermia (class_iii_antiarrhythmic, first line) — AHA 2020 ACLS Class IIb; in hypothermia limit to 1 dose until warmed >30 °C, then resume standard cadence
3. epinephrine 1 mg IV q3-5 min if normothermic; if core <30 °C → withhold further doses; if 30-34 °C → space q6-10 min IV modified for hypothermia (inotrope_chronotrope_vasopressor, first line) — AHA 2020 ACLS — modified dosing intervals for hypothermia given reduced metabolism + receptor responsiveness
4. magnesium sulfate 1-2 g IV IV one-time + repeat for TdP (electrolyte_anti_arrhythmic, add on) — AHA 2020 ACLS Class IIa for TdP; correct hypomagnesemia first
5. levothyroxine 200-500 µg IV loading → 50-100 µg IV daily IV daily (thyroid_hormone_replacement, comorbidity specific) — AACE myxedema coma management — IV levothyroxine + stress-dose steroids; precede T4 with hydrocortisone if adrenal insufficiency possible
6. hydrocortisone 100 mg IV q8h × 24-48h IV q8h (glucocorticoid_short_acting, comorbidity specific) — Standard adrenal crisis + myxedema coma management; precede levothyroxine with steroids to avoid precipitating crisis
7. propofol 5-50 µg/kg/min IV continuous; titrate RASS (sedative_iv_anesthetic, first line) — PADIS 2018; hepatic metabolism slowed in hypothermia → reduce dose during cooling phase
8. fentanyl 25-200 µg/h IV continuous (opioid_analgesic, first line) — PADIS 2018; analgesia + shivering suppression for TTM
9. tranexamic acid 1 g IV over 10 min IV within 3h of bleeding onset (antifibrinolytic, add on) — CRASH-2 PMID 20554319 if traumatic bleeding co-existing with hypothermic arrest

Setting playbook (outpatient) — Long-term cardiology / EP / endocrinology surveillance; ICD management if channelopathy or structural; substance-use long-term; mental health long-term; exposure prevention long-term
10. continue levothyroxine levothyroxine titrated to TSH PO daily — persistent hypothyroidism (AACE thyroid)
11. continue channelopathy regimen nadolol or propranolol per type PO daily — LQTS or CPVT (HRS 2017)
12. continue HF GDMT if structural CM sacubitril-valsartan + carvedilol + spironolactone + SGLT2i max tolerated PO as scheduled — structural CM HFrEF (ACC/AHA 2022 HF 4-pillar)

Non-pharmacologic actions:
- ICD/WCD adherence
- Cold-weather + alpine activity safety education
- Family CPR/AED ongoing
- Mental health long-term
- Substance-use recovery long-term
- Housing stability ongoing

AVOID / contraindication checks:
- Beta_blocker_avoid_acute_cardiogenic_shock (AHA 2020)
- Epinephrine_withhold_core_temp_below_30 (AHA 2020 hypothermia §)
- Defib_limit_to_1_attempt_at_core_temp_below_30 (AHA 2020 hypothermia §)
- Levothyroxine_precede_with_steroids_if_adrenal_insufficiency (AACE myxedema)

Monitoring

Regimen monitoring:
- continuous ecg telemetry (AHA 2020 Class I)
- serial troponin q3-6h x 24h (4th UDMI 2018)
- BMP q6-12h + Mg + K (rewarming-associated electrolyte derangement) (AHA 2020)
- continuous core temp via bladder or esophageal probe during warming and TTM (AHA 2020 + TTM2)
- continuous EEG for 24-48h (Sandroni 2021)
- NSE at 24h 48h 72h (Sandroni 2021) — interpret with caution given hypothermia confounding
- ABG q4-6h until pH and lactate stable (rewarming acidosis)
- CXR daily for pulmonary edema or VAP (rewarming-related)
- lactate q2-4h until normalized (SCAI 2022)

Setting (outpatient) monitoring:
- Quarterly BP + weight + symptom score
- Annual ECG + Holter if channelopathy
- Annual echo if HFrEF

Follow-up plan: 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
- Close-out criterion: cardiology + endo + substance-use + mental health + social work + rehab plan booked

Monitoring phase: 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

Disposition

Current setting: outpatient — Long-term cardiology / EP / endocrinology surveillance; ICD management if channelopathy or structural; substance-use long-term; mental health long-term; exposure prevention long-term

Disposition criteria:
- Long-term continuation; cross-link to cardio.hf.core.v1 for chronic HFrEF

Escalation triggers (move to higher acuity):
- ICD therapy delivered → urgent EP; consider catheter ablation per VANISH (PMID 27149033) if structural substrate
- EF declining despite GDMT → advanced HF eval
- Substance-use relapse with safety risk → urgent intervention

Earlier-Return Triggers

Return-precaution thresholds (watch for):
- [LIFE_THREATENING] Core temperature <28 °C with cardiac arrest — ECMO/CPB rewarming is gold standard (Walpoth 1997 PMID 9395428; ELSO accidental hypothermia consensus); favourable outcomes documented at very low core temperatures
- [LIFE_THREATENING] Recurrent VF or arrhythmia at core temp <30 °C — drugs less effective, defibrillation limited; bridge with ECMO rewarming
- [LIFE_THREATENING] Severe hypothermia + cardiac arrest meeting ECMO criteria — witnessed event, no obvious lethal trauma, K typically <12 mmol/L (Brown 2012 + ELSO consensus); ECMO/CPB rewarming offers favourable outcomes even at very low temperatures

Citations

- AHA 2020 ACLS / Post-Cardiac-Arrest Care hypothermia § + ERC 2021 accidental hypothermia + ELSO accidental hypothermia consensus + Brown 2012 NEJM + Walpoth 1997 NEJM ECMO + TTM2 + HYPERION + Sandroni 2021 neuroprog [PMID:33081530](https://pubmed.ncbi.nlm.nih.gov/33081530/)
- Cited evidence (PMID 23215559) [PMID:23215559](https://pubmed.ncbi.nlm.nih.gov/23215559/)
- Cited evidence (PMID 9395428) [PMID:9395428](https://pubmed.ncbi.nlm.nih.gov/9395428/)
- Cited evidence (PMID 34133859) [PMID:34133859](https://pubmed.ncbi.nlm.nih.gov/34133859/)
- Cited evidence (PMID 31532382) [PMID:31532382](https://pubmed.ncbi.nlm.nih.gov/31532382/)

Last reconciled with current guidelines: 2026-05-15.
References
  • AHA 2020 ACLS / Post-Cardiac-Arrest Care hypothermia § + ERC 2021 accidental hypothermia + ELSO accidental hypothermia consensus + Brown 2012 NEJM + Walpoth 1997 NEJM ECMO + TTM2 + HYPERION + Sandroni 2021 neuroprog — PMID:33081530
  • Cited evidence (PMID 23215559) — PMID:23215559
  • Cited evidence (PMID 9395428) — PMID:9395428
  • Cited evidence (PMID 34133859) — PMID:34133859
  • Cited evidence (PMID 31532382) — PMID:31532382