Hypothermia ❄️
Accidental hypothermia for on-call doctors: HPSC recognition (<35°C), RCUK 2025 Swiss staging, gentle handling, rewarming, arrhythmia risk below 30°C, and when to escalate for ECLS.
Scope
- This topic covers accidental hypothermia and peri-arrest care: educational content based on RCUK 2025. Follow your hospital's local protocol.
- Distinguish from therapeutic cooling / targeted temperature management after cardiac arrest, and from inadvertent perioperative hypothermia (different definition and pathway; see Related NICE guidance).
- HPSC cold weather advice supports recognition and vulnerable groups in Ireland; it is not a full rewarming pathway.
🚨 Red Flags / Escalation
- Core temperature <35°C or clinical signs of hypothermia: immediate medical review (HPSC).
- Impaired consciousness, absent or weak vital signs, or suspected Stage II–IV: senior / ED / critical care early.
- Per RCUK 2025, transfer patients with imminent-arrest risk or in cardiac arrest directly to an ECPR centre for rewarming if:
- Heart rate <45 min⁻¹
- Systolic BP <90 mmHg
- Ventricular arrhythmia
- Core temperature <30°C
- Arrest or peri-arrest: call the resuscitation team (often 2222), start ALS with hypothermia modifications below, and involve ICU / ECLS pathway early.
- Do not declare death until the patient is warm (or futility is agreed with seniors using local / HOPE-based prognostication).
🧠 Definition and differentials
- Accidental hypothermia (HPSC / RCUK framing): core body temperature <35°C from environmental or other non-therapeutic heat loss.
- Therapeutic cooling: deliberate temperature control after ROSC or for other indications. Do not manage as accidental hypothermia.
- Perioperative hypothermia: inadvertent cooling around surgery. NICE CG65 uses a peri-op threshold of core temperature <36°C. Use theatre / recovery warming protocols and the NICE link; this page is for accidental exposure and peri-arrest care.
📞 What to Ask / Orders to Make
- Exposure history: outdoors, immersion, wet clothes, inadequate heating, prolonged lie after fall, intoxication, sepsis, endocrine disease.
- Vulnerable group? Age >65 or <5, chronic cardiac / respiratory / kidney disease, disability, dementia, homelessness, fuel poverty (HPSC).
- Ask for: ABCDE, continuous cardiac monitoring, low-reading / core thermometer if available, 12-lead ECG, blood glucose, ABG / VBG, U&E (K⁺), FBC, coagulation, lactate.
- Remove wet clothing and start insulation while waiting for medical review. Handle gently: rough movement can precipitate VF.
- Confirm local ED hypothermia / ECLS referral pathway and nearest ECPR-capable centre.
📋 Assessment
- ABCDE with prolonged pulse / breathing check: up to 1 minute in an unconscious hypothermic patient (RCUK 2025).
- Measure core temperature with a low-reading thermometer when possible. If core temperature cannot be measured, use Swiss staging (below).
- HPSC recognition signs: cold covered skin (abdomen / axilla), shivering, drowsiness, slurred speech, slow breathing, confusion, incoordination, thready pulse.
- Look for reversible contributors: hypoxia, hypoglycaemia, sepsis, trauma, overdose, myxoedema, adrenal failure, stroke.
- ECG: bradycardia, Osborn (J) waves, atrial fibrillation, ventricular arrhythmias. Arrhythmia risk rises as temperature falls, especially <30°C.
Swiss staging (RCUK 2025)
- Use when core temperature cannot be measured, or alongside measured temperature.
Stage IMild
- Estimated core temp
- 35–32°C
- Clinical features
- Conscious with shivering
Stage IIModerate
- Estimated core temp
- 32–28°C
- Clinical features
- Impaired consciousness (confusion, lethargy); shivering may be reduced or absent
Stage IIISevere
- Estimated core temp
- 28–24°C
- Clinical features
- Unconscious, but vital signs (pulse, breathing) present
Stage IVDeep
- Estimated core temp
- <24°C
- Clinical features
- Vital signs absent
| Stage | Severity | Estimated core temp | Clinical features |
|---|---|---|---|
| Stage I | Mild | 35–32°C | Conscious with shivering |
| Stage II | Moderate | 32–28°C | Impaired consciousness (confusion, lethargy); shivering may be reduced or absent |
| Stage III | Severe | 28–24°C | Unconscious, but vital signs (pulse, breathing) present |
| Stage IV | Deep | <24°C | Vital signs absent |
💊 Management: circulation present
- Gentle handling at all times. Move to a warm environment; remove wet clothes; dry and insulate (blankets, forced-air warming per local protocol).
- Oxygen if hypoxic or unwell. IV access. Cardiac monitoring before and during rewarming.
- Rewarm according to local ED protocol. Typical measures: warm environment, insulation, active external warming, and warmed IV fluids if volume needed. Avoid rapid / rough movement.
- Correct hypoglycaemia, hypoxia, and other reversible causes. Treat concurrent illness (infection, trauma, intoxication).
- Stage I: often passive + active external rewarming and observation. Escalate if consciousness falls or vital signs deteriorate.
- Stage II–III: senior / ED / ICU involvement; continuous monitoring; prepare for arrhythmia and possible ECLS transfer if imminent-arrest criteria are met.
💊 Cardiac arrest and peri-arrest (RCUK 2025)
- Follow standard ALS as the foundation, then apply hypothermia modifications.
- Below 30°C: high arrhythmia risk. After three shocks for persistent VF, delay further defibrillation until core temperature >30°C.
- Below 30°C: adrenaline accumulates and may do more harm than good. Give IV adrenaline 1 mg (1:10,000) once core temperature reaches 30°C, unless imminent ECPR is planned.
- Core temperature 30–35°C: space adrenaline doses to every 6–10 minutes.
- Amiodarone: loading dose 300 mg if a shockable rhythm is present; delay further doses until core temperature >30°C.
- Core temperature <28°C: if immediate continuous CPR is not feasible, delay CPR or use intermittent CPR per RCUK guidance during prolonged transport.
- Consider a mechanical CPR device if transport is prolonged.
- Rewarm arrested patients with VA-ECMO (ECPR) when available. If an ECPR centre cannot be reached within a reasonable time (e.g. about 6 hours), start non-ECLS rewarming per local critical care protocol.
- In hospital, base prognostication of successful rewarming on the HOPE score (hypothermiascore.org or local tool), with senior decision-making.
Actions for interns
- Confirm the temperature is real: use an appropriate thermometer; do not dismiss a low reading in a vulnerable or exposed patient.
- Start gentle handling, dry insulation, monitoring, and ABCDE while calling for senior help.
- Document Swiss stage or measured core temperature, exposure history, and ECG findings.
- Know your hospital’s ED hypothermia pathway and how to escalate for ECLS / ECPR.
- Do not stop resuscitation solely because of prolonged downtime if hypothermia preceded arrest: discuss with seniors and follow RCUK / local ECLS criteria.
Based on
Related NICE guidance
NICENICE CG65 — Hypothermia: prevention and management in adults having surgery (updated Dec 2016)
Full guidance on nice.org.uk. BetterCall is not endorsed by NICE.
Note Template
Ready-to-use clinical note structure
🕒 08 / 10 / 2026 — 16:06 ATRP re: accidental hypothermia Patient: [age] [sex] Location: [ward / ED / other] Admission Dx: [reason for admission] PMHx: [frailty, dementia, cardiac/resp/renal disease, endocrine, alcohol/drugs] 🧾 Hx: • Exposure: [outdoors / immersion / wet clothes / inadequate heating / prolonged lie after fall / other] • Duration of exposure: [known / unknown] • Vulnerable group (HPSC): [>65 / <5 / chronic disease / disability / dementia / homelessness / fuel poverty / none] • Associated: [trauma / intoxication / sepsis / hypoglycaemia / other] 🩺 Exam: • Core temp: __ °C (method: [tympanic / rectal / oesophageal / bladder / other]) • Swiss stage: [I / II / III / IV / not applicable] • HR: __ BP: __ RR: __ SpO₂: __ GCS: __ • Shivering: [Y/N] Skin: [cold covered areas Y/N] • Handling: gentle; wet clothes removed: [Y/N] 🧪 Investigations: • ECG: [bradycardia / AF / VF/VT / Osborn waves / other] • Glucose: __ K⁺: __ ABG/VBG: [ ] Lactate: __ • Other: FBC, coagulation, septic screen [ ] 💊 Management: • Insulation / active external warming: [ ] • Warmed fluids: [Y/N] • Cardiac monitoring: [Y/N] • Arrest / peri-arrest: [Y/N] • If arrest (RCUK 2025): shocks __; adrenaline held until ≥30°C [Y/N]; amiodarone [ ] • ECPR / ECLS criteria considered: HR <45 / SBP <90 / ventricular arrhythmia / core <30°C: [met / not met] • Transfer to ECPR centre discussed: [Y/N] 📋 Impression: Accidental hypothermia Stage [ ] / core __ °C Likely cause: [exposure / immersion / post-fall / other] Haemodynamic status: [stable / peri-arrest / arrest] 📌 Plan: • Continue rewarming per [local ED protocol] • Senior / ICU / ECLS: [ ] • HOPE score if arrest for prognostication: [ ] • Family updated: [Y/N] 👤 [Your Name], [Role] IMC: _______
Educational reference only. Medical disclaimer