Metabolic, toxicology and environment

Accidental Hypothermia Algorithm

Stage it, rewarm by stage, modified ACLS below 30 °C

Reviewed by Alex G, BSN, RN, CEN, CCRN, CMC, NREMT-P · From the Reference tab of the app

Each step lists what to do, then the choices that lead on. In the app the algorithm is tapped through one decision at a time.

1 Handle gently and call for help: signs of life?

Call for help; if unconscious or unstable, alert the ECMO or cardiac surgery team early
Keep horizontal and move gently: rough handling can trigger VF; cut off wet clothes, insulate, warm the room
Monitor ECG; check pulse and breathing for up to 1 minute (ERC 2025); SpO₂ may not read on cold fingers
Core temperature with a low-reading probe: esophageal if intubated, otherwise epitympanic or bladder (rectal lags)

Pulse or breathing present → step 2 No signs of life → step 3

2 Which stage?

Stage by signs when core temperature cannot be measured (Swiss staging, ERC 2025)
Worse than the temperature explains: check glucose and look for drugs, head injury, stroke or sepsis

Stage 1: alert and shivering (about 35–32 °C) → step 4 Stage 2: drowsy or confused, shivering weak or gone (about 32–28 °C) → step 5 Stage 3: unconscious with pulse and breathing (about 28–24 °C) → step 6

3 Hypothermic cardiac arrest: CPR, call ECLS

Start CPR unless injury is obviously lethal or the body is frozen solid
Call the ECMO team now; ECLS center reachable within about 6 hours: transport with mechanical CPR
Below 28 °C, if continuous CPR is impossible during rescue: 5 minutes of CPR alternating with pauses of 5 minutes or less (10 below 20 °C, ERC 2021)
Pads on; measure core temperature to choose the drug and shock plan

Core below 30 °C, or not yet measured → step 7 Core 30 °C or more → step 8

4 Stage 1: rewarm actively

Remove wet clothes; dry, insulate and warm the room
Forced-air blanket or heat packs on the trunk
Warm sweet drinks if alert and able to swallow
Find the cause: alcohol, drugs, low glucose, injury, sepsis, hypothyroidism

Rewarming well → step 9 Drowsier, or shivering stops while still cold → step 5

5 Stage 2: active rewarming; any risk of arrest?

Keep horizontal and still; no standing or walking; continuous ECG
Forced-air warming of the trunk; warmed IV fluids (38–42 °C); warm humidified oxygen
Hypotension: warmed fluid boluses (cold diuresis leaves patients volume depleted)
Check glucose, potassium and a blood gas

HR under 45, SBP under 90, ventricular arrhythmia, or core under 30 °C → step 6 None of these: keep rewarming → step 9

6 High risk of arrest: ECLS-capable center

Transfer directly to a center that can start VA-ECMO or bypass (ERC 2025); call ahead; pads on, CPR ready
Intubate if needed with a gentle technique; warm humidified oxygen
Forced-air warming and warmed IV fluids; consider an intravascular warming catheter or a CRRT circuit
Arterial line; keep central line guidewires out of the heart (VF)
Below 28 °C, ECLS rewarming may be reasonable even with a pulse (AHA 2025, 2b)

Pulse lost → step 3 Stable and rewarming → step 9

7 Below 30 °C: limit shocks, hold epinephrine

VF or pulseless VT: one shock (AHA 2025) or up to three (ERC 2025); if VF persists, no more shocks until core reaches 30 °C
Hold epinephrine until core reaches 30 °C (ERC 2025; AHA 2025, 2b)
Amiodarone: ERC gives one 300 mg dose for a shockable rhythm, more only above 30 °C; AHA makes no recommendation
Keep compressions going and keep rewarming

Core reaches 30 °C → step 8 Decide on ECLS rewarming → step 10

8 30–35 °C: longer drug intervals

Epinephrine 1 mg every 6–10 minutes, twice the usual interval (ERC 2025)
Shocks per standard ACLS from 30 °C
Standard ACLS once core is above 35 °C

ROSC → step 9 No ROSC → step 10

9 After rewarming or ROSC

Rewarming shock: vasodilation unmasks volume loss; warmed fluid, then pressors
Recheck potassium, glucose, blood gas, lactate, CK, coagulation and platelets
Watch for arrhythmias, pulmonary edema, aspiration pneumonia, rhabdomyolysis, compartment syndrome, AKI and frostbite
Comatose after arrest: post-arrest temperature control (32–37.5 °C, prevent fever)
Find the cause: alcohol, drugs, low glucose, sepsis, hypothyroidism, adrenal insufficiency, stroke, trauma

End of this path.

10 Is ECLS rewarming worthwhile and within reach?

HOPE score (age, sex, asphyxia, CPR duration, potassium, temperature): survival 10% or more supports ECLS (AHA 2025)
No HOPE score: potassium 12 mmol/L or more predicts death in adults, though HOPE predicts better
Asphyxia before cooling (avalanche burial, drowning) lowers the odds
Do not use end-tidal CO₂ to predict outcome in hypothermic arrest (AHA 2025)

Candidate, ECLS available → step 11 Candidate, no ECLS within reach → step 12 HOPE under 10%, potassium 12 or more, or lethal injury → step 13

11 ECLS rewarming

VA-ECMO preferred over cardiopulmonary bypass (better survival, AHA 2025)
Compressions continue until flow starts
Rewarm at about 1.5–5 °C per hour (AHA 2025, 2b)
Expect swings in potassium, glucose and clotting; heparin per the ECMO team

Rewarmed with ROSC → step 9

12 No ECLS in reach: rewarm during CPR

Start non-ECLS rewarming if an ECLS center cannot be reached in about 6 hours (ERC 2025)
Warm lavage of the chest (through chest tubes) or peritoneum, an intravascular warming catheter, or a CRRT circuit
Warmed IV fluids, forced air, warm humidified oxygen; keep CPR going

ROSC → step 9 No ROSC after rewarming → step 13

13 Consider stopping resuscitation

Obvious lethal injury: decapitation, truncal transection, incineration, or frozen solid (AHA 2025)
HOPE survival under 10%, or potassium 12 mmol/L or more when HOPE cannot be scored
No ROSC after rewarming
The physician decides with the team; support the family and document