Hypothermia - Emergency Medicine

Quick Answer

One-liner: Hypothermia is a core temperature below 35°C requiring rapid rewarming; mild hypothermia (32-35°C) can be managed with passive rewarming, while severe hypothermia (below 28°C) demands active core rewarming, modified resuscitation, and prolonged CPR ("not dead until warm and dead").

Accidental hypothermia is defined as an involuntary drop in core body temperature below 35°C (95°F). It ranges from mild (32-35°C) where patients shiver and maintain cardiac output, to severe (below 28°C) where patients are comatose, bradycardic, and at high risk of ventricular fibrillation. Hypothermia provides neuroprotection by reducing cerebral metabolic rate by approximately 50% for every 10°C temperature drop, allowing survival after prolonged cardiac arrest. Management focuses on preventing further heat loss, rapid rewarming (passive for mild, active for moderate/severe), and modified resuscitation with prolonged CPR, up to three defibrillation attempts before rewarming to greater than 30°C, and withholding adrenaline below 30°C. "Not dead until warm and dead" is a critical principle - continue CPR until patient is rewarmed to at least 32-35°C unless there are obvious signs of irreversible death (e.g., serum potassium greater than 12 mmol/L, fatal injuries, or rigor mortis).

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ACEM Exam Focus

Primary Exam Relevance

• Physiology: Thermoregulation (hypothalamic set-point, shivering thermogenesis, non-shivering thermogenesis), cold-induced diuresis, decreased cerebral metabolic rate (Q10 effect), cold-induced diuresis, hemoconcentration, coagulopathy
• Pharmacology: Reduced drug metabolism below 30°C, adrenaline interval modifications, lidocaine toxicity in hypothermia, vasopressor effects
• Anatomy: Peripheral vasoconstriction (cutaneous circulation), countercurrent heat exchange, brown adipose tissue distribution

Fellowship Exam Relevance

• Written: Classification (mild/moderate/severe), Osborn J waves, passive vs active rewarming, ventricular fibrillation management, "not dead until warm and dead," frostbite management, HOPE score for prognosis
• OSCE: Hypothermic cardiac arrest resuscitation, frostbite assessment, ECG interpretation (Osborn waves), rewarming technique demonstration, Indigenous health communication
• Key domains tested: Medical Expert (clinical management), Collaborator (retrieval team coordination), Professional (ethical considerations in prolonged resuscitation)

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Key Points

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Epidemiology

Australian/NZ Specific

• Seasonal variation: Peak incidence June-August (Southern Hemisphere winter), with secondary peak in alpine regions during ski season (July-September) [16]
• Geographic distribution: Higher incidence in Tasmania, Victoria alpine regions, ACT, and rural NSW/Victoria due to colder temperatures. NT and Queensland have lower rates but higher mortality due to delayed presentation [17]
• Urban vs rural: Urban areas: 3-4 per 100,000/year; Rural/remote: 8-12 per 100,000/year due to outdoor occupations, homelessness, delayed access to care [18]
• Indigenous population: Aboriginal and Torres Strait Islander peoples 2-3× higher incidence of hypothermia-related presentations in remote communities, particularly neonatal cold stress and elderly environmental exposure [19][20]
• Māori population: Māori have 1.5-2× higher hypothermia mortality due to socioeconomic factors, rural residence, and comorbidities [21][22]
• Outdoor exposure: Bushwalkers, fishermen, skiers account for 40-50% of severe hypothermia cases in Australia/NZ [23]
• Alcohol/drug-related: 35-45% of adult hypothermia cases involve alcohol or substance use, increasing risk due to impaired judgment, vasodilation, and reduced shivering [24][25]

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Pathophysiology

Mechanism

Heat loss exceeds heat production: Hypothermia occurs when heat loss (radiation, conduction, convection, evaporation) exceeds thermogenic capacity (shivering, non-shivering thermogenesis, basal metabolic rate). The hypothalamus (preoptic area) detects temperature deviation from set-point (~37°C) and activates compensatory responses:

1. Peripheral vasoconstriction: Reduced blood flow to skin and extremities to conserve core heat, causing cold extremities, peripheral cyanosis, and reduced heat loss through radiation
2. Shivering thermogenesis: Skeletal muscle contraction increases heat production 3-5× basal rate, effective above 32°C. Requires ATP and glycogen, impaired by malnutrition, exhaustion, alcohol
3. Non-shivering thermogenesis: Brown adipose tissue (BAT) activation via sympathetic stimulation (β3-adrenergic receptors) uncouples oxidative phosphorylation, producing heat. Most active in infants, limited in adults
4. Behavioral responses: Seeking shelter, adding clothing, huddling (impaired in intoxication, dementia, neurological injury)

Cold-induced physiological changes:

Pathological Progression

Cold exposure → Heat loss > Heat production
    ↓
Core temperature below 35°C → Hypothermia
    ↓
Mild (32-35°C): Shivering, tachycardia, tachypnoea, ataxia → Conscious
    ↓
Moderate (28-32°C): Shivering ceases, bradycardia, confusion, arrhythmias (AF, J-waves) → Impaired consciousness
    ↓
Severe (below 28°C): Coma, VF risk, marked bradycardia, hypotension → Cardiac arrest possible
    ↓
Profound (below 24°C): Apparent death, asystole/VF, rigid muscles → Cardiac arrest
    ↓
Outcome: Survival with rapid rewarming + ECMO (if below 28°C arrest) OR Death if delayed/potassium greater than 12 mmol/L

Why It Matters Clinically

• Neuroprotection: For every 10°C drop, cerebral metabolic rate decreases ~50%, allowing tolerance of prolonged hypoxia/ischaemia. Patients can survive greater than 60 minutes cardiac arrest if cooled before arrest (e.g., immersion hypothermia) [26][27]
• Cold heart irritability: Temperatures below 28°C cause myocardial instability due to altered ion channel function (delayed depolarization, prolonged repolarization), increasing VF risk with minimal stimuli (movement, intubation, central line) [28][29]
• Afterdrop phenomenon: During rewarming, cold peripheral blood returns to core, causing further temperature drop (1-3°C) and risk of core cooling. Minimize by focusing rewarming on trunk, avoiding extremity heating [30][31]
• Drug metabolism: Hepatic enzyme activity decreases 50% per 10°C below normal, leading to prolonged drug half-lives (e.g., adrenaline, lidocaine, opioids). Dosing must be modified [32][33]
• Rewarming shock: Peripheral vasodilation during rewarming causes relative hypovolaemia due to cold diuresis and hemoconcentration. Requires aggressive IV fluid resuscitation (warm 38-42°C crystalloids) [34][35]

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Clinical Approach

Recognition

Trigger suspicion for hypothermia in:

• Outdoor exposure (bushwalking, fishing, skiing, homelessness)
• Cold environment immersion (water, mud, snow)
• Alcohol/drug intoxication in cold weather
• Elderly or infant with altered mental status in winter
• Trauma with prolonged field time
• Unexplained bradycardia, altered mental status, or cold extremities

Key discriminators from other conditions:

Initial Assessment

Primary Survey

• A (Airway): Assess patency. Jaw thrust (not head tilt) if cervical spine injury suspected. Hypothermic patients may have decreased airway reflexes → aspiration risk
• B (Breathing): Respiratory rate may be slow and shallow. Look for paradoxical breathing, apnoea. Auscultate for crackles (pulmonary oedema from cold stress). SpO2 may be inaccurate with cold peripheral vasoconstriction
• C (Circulation): Palpate central pulse (carotid/femoral) for up to 1 minute (bradycardia may be extreme). Check capillary refill (prolonged). Assess skin temperature (cold extremities vs warm core). Monitor BP (hypotension common in moderate-severe). ECG monitoring critical (Osborn waves, arrhythmias)
• D (Disability): AVPU/GCS assessment. Confusion common in moderate hypothermia, coma in severe. Pupils may be fixed/dilated in profound hypothermia (not death). Check glucose (hypoglycaemia can mimic or coexist)
• E (Exposure): Remove wet clothing, prevent further heat loss (insulation, vapour barrier). Check for frostbite (fingers, toes, ears, nose). Assess for trauma (falls, immersion injuries)

History

Key Questions

Red Flag Symptoms

Examination

General Inspection

• General appearance: Shivering (mild) or absent shivering (moderate-severe). Patients may be curled in fetal position (heat conservation). Altered mental status (confusion, slurred speech, ataxia, coma). Skin pale, cool, cyanosed peripherally. May have wet clothing from immersion or precipitation
• Vital signs: Temperature (core: low-reading rectal, oesophageal, or bladder probe). HR: Bradycardic relative to temperature (expected HR ≈ 60 beats/min at 28°C). BP: Hypotensive in moderate-severe. RR: Slow, shallow. SpO2: May be falsely low due to peripheral vasoconstriction
• Skin: Check for frostnip (pale, numb, painless with warming), frostbite (white/yellow, hard, numb, painless after thawing), trench foot (chronic cold exposure: red, swollen, painful, no tissue freezing)

Specific Findings

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Investigations

Immediate (Resus Bay)

Standard ED Workup

Advanced/Specialist

Point-of-Care Ultrasound

Hypothermia POCUS applications:

• Cardiac: Confirm cardiac activity vs asystole (important - absent motion may be reversible in hypothermia). Exclude pericardial tamponade. Assess ventricular function (often globally depressed in moderate-severe hypothermia). Guide central line placement (often difficult due to vasoconstriction)
• Lung: Assess for pulmonary oedema (B-lines), pneumothorax (absence of lung sliding)
• Abdominal: FAST scan for free fluid (hypothermia may mask bleeding signs)
• Vascular: Assess for deep vein thrombosis (cold-induced coagulopathy + immobility)

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Management

Immediate Management (First 10 minutes)

1. Remove from cold environment immediately (5 minutes)
   - Move to warm, dry shelter
   - Remove wet clothing (minimizing movement)
   - Prevent further heat loss (insulation + vapour barrier)

2. Assess ABCDE (2 minutes)
   - Airway: Jaw thrust (no head tilt if C-spine injury)
   - Breathing: Assisted ventilation if respiratory rate below 10/min or SpO2 below 94%
   - Circulation: Palpate central pulse for 1 minute. ECG monitoring (Osborn waves, arrhythmias)
   - Disability: AVPU/GCS. Glucose check
   - Exposure: Full inspection, prevent heat loss

3. Measure core temperature (1 minute)
   - Low-reading rectal, oesophageal (intubated), or bladder probe
   - Classify severity: Mild (greater than 32°C), Moderate (28-32°C), Severe (below 28°C)

4. Initiate appropriate rewarming (2 minutes)
   - Mild (greater than 32°C): Passive rewarming (insulation, blankets)
   - Moderate (28-32°C): Active external (forced-air, warm packs)
   - Severe (below 28°C): Active internal (warm IV fluids, lavage, ECMO for arrest)

5. Handle GENTLY throughout (ONGOING)
   - Minimize movement and procedures that may precipitate VF (below 30°C)
   - Avoid rough handling, vigorous suctioning, rapid central line insertion
   - Explain "cold heart" concept to team

Resuscitation (if applicable)

Airway

• Mild to moderate hypothermia (greater than 30°C): Standard airway management. Oropharyngeal/nasopharyngeal airway if GCS below 9. Consider early intubation if respiratory compromise (RR below 10, SpO2 below 94%, decreased consciousness). RSI with modified doses (reduce induction agents 50% if below 32°C)
• Severe hypothermia (below 30°C): Intubation indicated for GCS below 8, respiratory failure, or cardiac arrest. Handle airway gently (movement can precipitate VF). Use cuffed tube. Warm humidified oxygen (40-45°C). Confirm tube placement with capnography (EtCO2 target 35-40 mmHg). Consider mechanical ventilator for prolonged ventilation

Breathing

• Oxygenation: High-flow oxygen (10-15 L/min via non-rebreather mask) for spontaneous breathing patients. Target SpO2 94-98% (corrected for temperature - left shift oxyhaemoglobin curve may falsely elevate SpO2)
• Ventilation: For intubated patients, tidal volume 6-8 mL/kg, rate 10-12/min (may need lower rate below 30°C to avoid auto-PEEP). PEEP 5-10 cmH2O (up to 15-20 cmH2O for severe hypoxaemia). Warm humidified gases (40-45°C)
• Monitoring: Continuous capnography. EtCO2 below 10 mmHg indicates ineffective CPR. EtCO2 greater than 35-40 mmHg suggests good perfusion/ROSC

Circulation

Hypothermic cardiac arrest management (Modified ALS):

1. Start CPR immediately (continuous if possible)
   - Chest compressions 100-120/min, depth 5-6 cm
   - Compression:ventilation ratio 30:2 (single rescuer), 15:2 (two rescuers)
   - Minimize interruptions (below 10 seconds)
   - Consider mechanical CPR device for prolonged resuscitation

2. Assess rhythm, defibrillate if VF/pVT
   - Up to 3 stacked shocks (if immediately available, below 20 seconds)
   - Biphasic energy: 120-200J
   - If refractory after 3 shocks → REWARM to greater than 30°C before further attempts
   - Dry chest before pads (water conducts current)

3. Airway and breathing
   - Intubate early (if available skills)
   - Warm humidified oxygen (40-45°C)
   - Capnography monitoring (EtCO2 target 35-40 mmHg)

4. IV access and medications (MODIFIED)
   - Give warm IV fluids (38-42°C crystalloid)
   - Withhold ADRENALINE if core temperature below 30°C
   - If 30-34°C: Adrenaline 1 mg IV every 6-10 MINUTES (standard is 3-5 minutes)
   - If greater than 34°C: Standard dosing (1 mg IV every 3-5 minutes)
   - Consider amiodarone 300 mg IV (load) if VF refractory to defibrillation
   - Reduced metabolism: Drug effects prolonged

5. Active rewarming (CRITICAL)
   - ECMO/ECLS is GOLD STANDARD for hypothermic arrest below 28°C
   - Transfer to ECMO centre immediately (do NOT stop CPR for transfer)
   - Non-ECLS rewarming:
     * Forced-air warming blankets (trunk focus, avoid extremities initially)
     * Warm IV fluids (38-42°C, rapid infusion)
     * Warm humidified oxygen (40-45°C)
     * Peritoneal/thoracic lavage (38-42°C saline) in severe cases

6. Continue CPR until REWARMED
   - "Not dead until warm and dead"
   - Continue until core temperature 32-35°C AND no ROSC
   - Consider futility if: Serum potassium greater than 12 mmol/L, fatal injuries, rigor mortis, chest wall frozen

7. Reassess after rewarming to greater than 30°C
   - Check rhythm, defibrillate if VF/pVT
   - Resume standard ALS protocols if greater than 32°C
   - Consider termination if no ROSC at 35°C with treatable causes excluded

Modified CPR for transport:

• Continuous CPR preferred: Maintain compressions during transport if possible
• Intermittent CPR (if continuous impractical): 5 minutes CPR minimum, then up to 5 minutes without CPR, resume CPR ASAP. This is better than no CPR in severe hypothermia (below 28°C) [36]
• Mechanical CPR devices: Useful for prolonged resuscitation, transport, ECMO cannulation. Devices: LUCAS, AutoPulse, ZOLL

Medications

Paediatric Dosing

Ongoing Management

Rewarming techniques by severity:

Rewarming complications management:

• Afterdrop: Monitor core temperature closely during rewarming. Continue active rewarming until afterdrop stabilizes. Aggressive warm IV fluids
• Rewarming shock: Peripheral vasodilation causes relative hypovolaemia. Give warm crystalloids (38-42°C) 20-30 mL/kg bolus, titrate to MAP greater than 65 mmHg. Consider vasopressors (noradrenaline) if refractory
• Arrhythmias: VF most common below 28°C. Treat with defibrillation (up to 3 shocks), then rewarm. Amiodarone for refractory VF greater than 30°C. Handle gently to prevent iatrogenic VF
• Pulmonary oedema: From cold stress, rewarming, fluid resuscitation. Diuretics (furosemide 20-40 mg IV) if overload, CPAP support
• Coagulopathy: Prolonged PT/APTT, bleeding. Correct with FFP, platelets, cryoprecipitate if bleeding or before invasive procedures. Avoid unnecessary invasive procedures until greater than 32°C
• Rhabdomyolysis: From prolonged immobility, frostbite. Monitor CK, renal function. Aggressive IV fluids, urine alkalinisation (sodium bicarbonate) if CK greater than 5,000 IU/L

Definitive Care

Admission criteria:

• Core temperature below 35°C with inability to maintain normothermia (e.g., elderly, malnourished, endocrine dysfunction)
• Moderate hypothermia (28-32°C) requiring active rewarming
• Severe hypothermia (below 28°C) regardless of clinical status
• Hypothermia with comorbidities (cardiac disease, sepsis, trauma, metabolic derangements)
• Frostbite requiring surgical assessment (deep tissue injury)

ICU/HDU criteria:

• Severe hypothermia (below 28°C)
• Hypothermic cardiac arrest requiring ECMO
• Cardiovascular instability (hypotension, arrhythmias) despite rewarming
• Respiratory failure requiring mechanical ventilation
• Coagulopathy with bleeding
• Multiorgan dysfunction (renal, hepatic, cerebral)

Definitive management:

• ECMO centre: For hypothermic cardiac arrest below 28°C. Transfer with continuous CPR. ECMO provides circulatory support + rapid rewarming
• Cardiology monitoring: Continuous ECG for arrhythmias, especially during rewarming. Temporary pacing may be required for bradyarrhythmias
• Surgical referral: For frostbite (plastic surgery, vascular surgery), necrotic tissue debridement, amputation if necessary (delayed 1-3 months for demarcation)
• Rehabilitation: Physical therapy for frostbite recovery, neurological rehabilitation if hypoxic brain injury, psychological support (post-traumatic stress from near-death experience)

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Disposition

Admission Criteria

• All patients with core temperature below 32°C requiring active rewarming
• Severe hypothermia (below 28°C) regardless of clinical status
• Hypothermic cardiac arrest patients (post-ROSC)
• Hypothermia with significant comorbidities (cardiac, respiratory, renal failure, sepsis, trauma)
• Frostbite requiring surgical assessment (deep tissue injury)
• Social factors: homelessness, inadequate housing, inability to maintain normothermia at home

ICU/HDU Criteria

• Severe hypothermia (below 28°C)
• Hypothermic cardiac arrest patients (pre- or post-ECMO)
• Cardiovascular instability (SBP below 90 mmHg, arrhythmias) despite active rewarming
• Respiratory failure requiring mechanical ventilation (RR below 8, PaO2 below 60 mmHg on 6L oxygen, GCS below 8)
• Coagulopathy with clinically significant bleeding
• Multiorgan dysfunction (AKI creatinine greater than 200 μmol/L, bilirubin greater than 50 μmol/L, lactate greater than 4 mmol/L)
• Requirement for invasive monitoring (arterial line, CVP)

Discharge Criteria

• Core temperature ≥35°C and stable for ≥2 hours
• Normal mental status (GCS 15, orientation normal)
• Stable cardiovascular parameters (HR 60-100, SBP greater than 100 mmHg, no arrhythmias)
• Normal respiratory status (RR 12-20, SpO2 greater than 94% on room air)
• No evidence of frostbite requiring ongoing care
• Adequate social support and shelter (homelessness requires alternative disposition)
• Able to maintain normothermia (appropriate clothing, heating access)
• Red flags to return: recurrent hypothermia symptoms, altered mental status, chest pain, dyspnoea, frostbite progression

Follow-up

• GP letter: Detail hypothermia episode, investigations, management, disposition. Emphasize prevention: appropriate clothing, avoid alcohol in cold, seek shelter early
• Specialist referral:
  • Cardiology if arrhythmias, myocardial injury (elevated troponin)
  • Vascular/plastic surgery for frostbite requiring ongoing care or potential amputation
  • Endocrinology if underlying endocrine dysfunction (hypothyroidism, diabetes)
  • Social work for homelessness, inadequate housing, elderly living alone
• Patient education:
  • "Prevention: Wear layers, waterproof outer layer, keep head/hands/feet covered, stay dry, avoid alcohol in cold, carry emergency supplies (blankets, high-energy food)"
  • "Recognition: Early signs of hypothermia (shivering, confusion, cold extremities) - seek shelter immediately"
  • "Frostbite prevention: Keep extremities warm and dry, avoid tight clothing, check sensation regularly"
• Community referral: Homeless services, aged care assessment, occupational health for outdoor workers

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Special Populations

Paediatric Considerations

Unique vulnerability:

• Higher surface area-to-volume ratio: Heat loss 2-3× faster than adults
• Limited shivering capacity: Immature thermoregulation, less effective shivering
• Brown adipose tissue: More active in infants (below 1 year) for non-shivering thermogenesis
• Inability to communicate: Infants/young children cannot report cold symptoms

Management modifications:

• Core temperature: Low-reading rectal probe preferred (bladder probes too small for most children)
• Rewarming: More aggressive due to faster heat loss. Use forced-air warming blankets with pediatric attachments. Warm IV fluids (38-40°C) at 10-20 mL/kg
• Medications: Weight-based dosing. Reduce induction agents 50% for RSI if below 32°C. Adrenaline 0.01 mg/kg (1:10,000)
• Frostbite: More common in children (hands/feet due to playing outside without gloves/boots). Higher risk of long-term sequelae (growth plate injury)
• Neonatal hypothermia: Critical issue in remote Indigenous communities. Thermal stress during retrieval. Incubator with humidity control. Kangaroo care (skin-to-skin) for stabilization

Prognosis: Children have better neurologic outcomes after hypothermic cardiac arrest compared to adults due to greater neuroplasticity and more rapid cooling (higher water content). Survival greater than 70% with ECMO for hypothermic arrest below 30°C [37][38]

Pregnancy

Physiological considerations:

• Increased metabolic rate: Higher baseline heat production (20-30% above non-pregnant)
• Peripheral vasodilation: Reduced vasoconstriction capacity, increased heat loss
• Gravid uterus: After 20 weeks, compresses inferior vena cava when supine → reduced venous return, hypotension worsened by hypothermia
• Fetal vulnerability: Fetal temperature follows maternal temperature. Hypothermia causes fetal bradycardia, distress, risk of teratogenicity if severe

Management modifications:

• Positioning: Left lateral tilt (15-30°) after 20 weeks to relieve aortocaval compression, especially during CPR
• Monitoring: Continuous fetal heart rate monitoring if greater than 20 weeks gestation and viable (typically greater than 24 weeks). Fetal bradycardia indicates maternal hypothermia severity
• Rewarming: Similar to non-pregnant, but prioritize maternal core temperature ≥35°C to protect fetus. Active internal rewarming (warm IV fluids, forced-air) preferred
• CPR modifications: Standard CPR with left lateral tilt. Consider perimortem caesarean section if no ROSC after 4-5 minutes of maternal arrest and uterus palpable above umbilicus (20+ weeks) [39][40]
• Medications: Most drugs cross placenta. Teratogenic risk lower than risk of maternal death. Use standard hypothermia medication modifications (adrenaline withheld below 30°C)
• ECMO: VA-ECMO can support both mother and fetus if required. Transfer to ECMO centre with obstetric capability

Prognosis: Maternal survival similar to non-pregnant if rapid rewarming achieved. Fetal outcome depends on duration and severity of hypothermia. Fetal survival possible even after prolonged maternal arrest if cooled before arrest (neuroprotective effect)

Elderly

Increased vulnerability:

• Reduced thermoregulation: Decreased shivering response, impaired vasoconstriction, reduced brown adipose tissue
• Comorbidities: Cardiovascular disease, diabetes, hypothyroidism, malnutrition increase risk
• Medications: β-blockers, sedatives, antipsychotics impair thermoregulation and shivering
• Social factors: Living alone, inadequate heating, limited mobility increase exposure risk

Management modifications:

• Slower rewarming: Avoid rapid rewarming (greater than 2°C/hour) due to reduced cardiovascular reserve. Monitor for arrhythmias, pulmonary oedema
• Aggressive monitoring: Continuous ECG (high arrhythmia risk), frequent temperature checks (every 15-30 minutes during rewarming)
• Medication review: Review β-blockers (may prevent compensatory tachycardia), sedatives (reduce shivering), anticoagulants (bleeding risk with frostbite)
• Social assessment: Assess home environment, heating, support systems. Involve social work for inadequate housing, living alone, inability to self-care
• Prognosis: Higher mortality (up to 50% in severe hypothermia) due to comorbidities, reduced physiologic reserve. However, good outcomes possible with appropriate management

Indigenous Health

Important Note: Aboriginal and Torres Strait Islander considerations:

Health disparities:

• 2-3× higher incidence of hypothermia-related presentations compared to non-Indigenous Australians, particularly in remote communities [19][20]
• Higher mortality from environmental hypothermia due to delayed presentation, limited healthcare access, comorbidities
• Neonatal hypothermia is a major contributor to infant mortality (2-3× higher than non-Indigenous infants) - thermal stress during long-distance retrievals from remote communities [41][42]
• Elderly Indigenous Australians at particular risk due to inadequate housing, energy poverty (inability to afford heating), living alone in remote communities

Cultural safety:

• Involve Aboriginal Health Workers (AHWs) and Aboriginal Liaison Officers (ALOs) early in care - they facilitate communication, provide cultural context, build trust
• Use culturally appropriate communication: avoid direct confrontation, use "yarning" (storytelling) approach, allow family/community presence during treatment
• Respect cultural protocols around death and dying: involve family in discussions about prolonged resuscitation, "not dead until warm and dead" concept
• Consider men's and women's business: some clinical discussions/examinations may require same-gender clinicians or family members present

Communication barriers:

• Language diversity: Use interpreters for patients with limited English proficiency (many remote communities have traditional languages)
• Health literacy: Explain medical concepts simply, use visual aids, check understanding (teach-back method)
• Mistrust of healthcare system: Build rapport through AHW involvement, explain all procedures, obtain informed consent clearly

Geographic barriers:

• Remote communities: Limited access to emergency care, long retrieval times (RFDS), limited local resources (no forced-air warmers, no ECMO capability)
• Housing conditions: Inadequate insulation, lack of heating, overcrowding increase hypothermia risk
• Outdoor activities: Traditional hunting/fishing, mustering increase exposure risk. Education on prevention critical

Clinical implications:

• Consider coexisting conditions: Higher prevalence of diabetes, cardiovascular disease, renal disease, rheumatic heart disease - complicates hypothermia management
• Medication interactions: Higher rates of β-blocker, ACE inhibitor use - may impair physiologic response to cold
• Social disposition: Many Indigenous patients return to inadequate housing. Arrange social work support, temporary housing if needed before discharge

Important Note: Māori health considerations:

Health disparities:

• 1.5-2× higher hypothermia mortality compared to non-Māori New Zealanders [21][22]
• Higher incidence of environmental hypothermia in rural Māori communities due to outdoor occupations, inadequate housing, socioeconomic factors
• Māori infants have 1.5-2× higher neonatal hypothermia rates, contributing to infant mortality gap

Cultural safety (tikanga and manaakitanga):

• Whānau involvement: Extended family central to decision-making. Involve whānau early in treatment, resuscitation decisions, discharge planning
• Manaakitanga (care and respect): Show respect for patient and whānau, explain protocols, involve kaumātua (elders) in cultural aspects of care
• Tikanga (customary practices): Respect cultural protocols around physical contact (some whānau prefer same-gender clinicians), spiritual practices (prayer, karakia), death rituals (tangi, body handling)
• Kaitiakitanga (guardianship): Recognize whānau as guardians of patient's wellbeing. They should be informed of all major decisions

Communication considerations:

• Use Māori Health Workers or cultural liaisons when available
• Incorporate te reo Māori (Māori language) where appropriate: greetings (kia ora), acknowledgment of whānau, use of culturally appropriate terms
• Allow whānau to perform cultural practices during treatment (prayer, blessing) - this supports wellbeing and should be facilitated

Healthcare access barriers:

• Rural location: Many Māori live in rural areas with limited healthcare access, longer retrieval times
• Socioeconomic factors: Higher rates of unemployment, inadequate housing, energy poverty increase hypothermia risk
• Distrust of healthcare system: Historical trauma affects trust. Build rapport through cultural safety, whānau involvement

Clinical implications:

• Consider comorbidities: Higher prevalence of cardiovascular disease, diabetes, respiratory disease in Māori populations
• Medication review: Higher use of β-blockers, cardiovascular medications may affect cold response
• Social disposition: Arrange whānau support, temporary housing, social services before discharge to prevent recurrence

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Pitfalls & Pearls

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Viva Practice

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OSCE Scenarios

Station 1: Hypothermic Cardiac Arrest Resuscitation

Format: Resuscitation Station Time: 11 minutes Setting: ED resuscitation bay

Candidate Instructions:

You are the team leader managing a 45-year-old male found collapsed after 12 hours exposure to -2°C overnight. He is unresponsive, pulseless, apnoeic. Paramedics report core temperature 27°C and ECG showing ventricular fibrillation. You have a nurse and registrar to assist. Manage this patient according to hypothermia cardiac arrest protocols.

Examiner Instructions: Patient is a manikin. Monitor shows VF, temperature 27°C. Candidate should demonstrate modified hypothermia cardiac arrest management. Team member (nurse/registrar) will follow instructions and ask clarifying questions.

Actor/Patient Brief: N/A (manikin station)

Marking Criteria:

Total: /11

Expected Standard:

• Pass: ≥6/11
• Key discriminators:
  • Withholds adrenaline below 30°C (critical - fail if gives standard dosing)
  • Limits defibrillation to 3 shocks before rewarming (critical - fail if continues defibrillating without rewarming)
  • States "not dead until warm and dead" principle (critical - fail if suggests early termination)
  • Starts active rewarming early (pass - fail if only passive rewarming)

Station 2: Moderate Hypothermia Assessment and Management

Format: Clinical Reasoning Station Time: 11 minutes Setting: ED cubicle

Candidate Instructions:

A 65-year-old male presents after 3 hours exposure to 5°C rain. He is confused, slurred speech, ataxic. You have assessed him and found core temperature 30°C. The ECG shows sinus bradycardia (HR 48/min) with Osborn J waves. Please explain your assessment and management plan to the examiner.

Examiner Instructions: Ask candidate to classify hypothermia severity, explain ECG findings, outline immediate management, discuss disposition. Provide prompts if needed: "What medication modifications are required?"

• "What complications might occur during rewarming?"

Actor/Patient Brief: N/A (candidate-examiner station)

Marking Criteria:

Total: /11

Expected Standard:

• Pass: ≥6/11
• Key discriminators:
  • Correctly classifies moderate hypothermia (fail if misclassifies as mild or severe)
  • Recognizes Osborn J waves and explains significance (fail if misses this finding)
  • Starts active external rewarming, not just passive (fail if only insulation)
  • Correctly modifies medication intervals (fail if gives standard adrenaline dosing)

Station 3: Frostbite Assessment and Patient Education

Format: Communication and Clinical Reasoning Station Time: 11 minutes Setting: ED examination room

Candidate Instructions:

A 28-year-old male presents after 4 hours skiing at -8°C. He reports numbness and white appearance of both hands. You have examined him and found Grade 2 frostbite (blisters forming after initial rewarming). The patient is anxious about potential amputation. Please assess the frostbite, explain management, and provide education to the patient.

Examiner Instructions: Candidate will interact with patient actor. Assess frostbite severity, explain rewarming technique, provide pain management, discuss prognosis and follow-up. Patient will express anxiety about amputation, ask questions about recovery time.

Actor/Patient Brief: You are a 28-year-old male skier. Your hands are numb and have white patches. You're worried about losing your fingers. You want to know:

• Will I need amputation?
• How long until I recover?
• Will I be able to ski again?
• What can I do to prevent this in the future? Be anxious but receptive to clear explanations. Ask follow-up questions.

Marking Criteria:

Total: /11

Expected Standard:

• Pass: ≥6/11
• Key discriminators:
  • Correctly identifies Grade 2 frostbite (fail if misclassifies)
  • Provides realistic prognosis without overpromising (fail if guarantees no amputation)
  • Explains rapid rewarming technique clearly (fail if misses key steps)
  • Addresses patient anxiety with empathy (fail if dismissive)

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SAQ Practice

Question 1 (8 marks)

Stem: A 38-year-old female is found collapsed in a remote alpine area after 16 hours overnight exposure to -8°C. She is unresponsive, pulseless, with core temperature 25°C. ECG shows ventricular fibrillation. Paramedics have initiated CPR and provided 3 shocks without ROSC.

Question: Outline your management of this hypothermic cardiac arrest, including medication modifications, rewarming strategy, and prognostication.

Model Answer:

• Immediate management (2 marks):

  • Continue high-quality CPR (100-120/min, depth 5-6 cm, minimal interruptions)
  • Up to 3 defibrillation shocks delivered (already done by paramedics) - no further shocks until rewarming
  • Intubate early for airway protection and effective ventilation, provide warm humidified oxygen (40-45°C)
  • Continuous capnography monitoring (target EtCO2 35-40 mmHg)

• Medication modifications (2 marks):

  • Withhold adrenaline - core temperature 25°C (below 30°C), drug metabolism severely reduced (~12% of normal)
  • If greater than 30°C, give adrenaline 1 mg IV every 6-10 minutes (double standard interval)
  • Consider amiodarone 300 mg IV if VF refractory to defibrillation after rewarming greater than 30°C
  • Reduce induction agents 50% for RSI (if intubation not already performed)

• Rewarming strategy (2 marks):

  • "Immediate: Forced-air warming blankets applied to trunk (armpit, chest, back) - avoid extremities initially (afterdrop prevention)"
  • "Active internal: Warm IV fluids (38-42°C) rapid infusion, warm humidified oxygen (40-45°C)"
  • "ECMO transfer: URGENT transfer to ECMO centre (gold standard for hypothermic arrest below 28°C). Do NOT stop CPR for transfer - maintain continuous or intermittent CPR (5 min on, up to 5 min off)"
  • "Non-ECLS rewarming (if ECMO not available): Consider peritoneal lavage (38-42°C saline via dialysis catheter) or thoracic lavage (via chest tubes) for refractory cases"

• Prognostication (2 marks):

  • ""Not dead until warm and dead": Continue CPR until core temperature reaches 32-35°C before considering termination"
  • "Serum potassium: Critical prognostic indicator. below 8 mmol/L = potentially salvageable, 8-10 mmol/L = guarded, greater than 12 mmol/L = generally futile (cell lysis before cooling)"
  • "HOPE score: Hypothermia Outcome Prediction after ECLS score uses age, sex, mechanism (asphyxia vs non-asphyxia), potassium, temperature to predict survival"
  • "Mechanism: Non-asphyxic hypothermia (this case - exposure hypothermia) has better prognosis than asphyxic (avalanche burial, drowning) if potassium below 8 mmol/L"

Examiner Notes:

• Accept: Mention of mechanical CPR device for prolonged resuscitation, discussion of intermittent CPR if continuous not possible during transport, mention of futility criteria (fatal injuries, rigor mortis, chest wall frozen)
• Do not accept: Giving adrenaline below 30°C (this is incorrect and dangerous), defibrillating more than 3 shocks before rewarming, stopping CPR without rewarming to 32-35°C

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Question 2 (6 marks)

Stem: A 62-year-old male with history of atrial fibrillation presents after 2 hours exposure to 4°C rain. He is alert but confused, shivering. Core temperature 34°C. ECG shows atrial fibrillation with ventricular response 70/min and small Osborn J waves.

Question: How would you manage this mild hypothermia with atrial fibrillation?

Model Answer:

• Classification (1 mark):

  • "Mild hypothermia (32-35°C): Shivering present, alert but confused. Shivering indicates intact thermogenesis"
  • "ECG findings: AF common in hypothermia 28-32°C (this patient 34°C - likely pre-existing AF exacerbated by cold stress). Small Osborn J waves suggest early myocardial irritability"

• Immediate management (2 marks):

  • "Passive rewarming: Remove wet clothing, full body insulation with wool blankets and vapour barrier (plastic wrap), warm room"
  • "Shivering support: Provide high-carbohydrate oral fluids (juice, warm sweet drinks) to fuel shivering heat generation. Avoid alcohol, caffeine, smoking (impair thermoregulation)"
  • "Monitoring: Continuous cardiac monitoring (arrhythmia risk), repeat core temperature every 30-60 minutes, monitor for afterdrop during rewarming"
  • "ABCDE assessment: Airway patent, breathing adequate (supplemental O2 if SpO2 below 94%), circulation stable, disability (confusion - monitor for deterioration), exposure (check for frostbite)"

• AF management (1 mark):

  • "Rate control: Ventricular response 70/min is adequate - no specific rate control required"
  • "Consider underlying cause: Cold stress exacerbates AF, may resolve with rewarming"
  • "Anticoagulation: If CHA2DS2-VASc score indicates anticoagulation, continue existing therapy. Do not initiate new anticoagulation in acute hypothermia (coagulopathy risk)"
  • "Cardioversion: Not indicated in acute hypothermia - AF often resolves with rewarming"

• Disposition (1 mark):

  • Admit to ward/HDU for observation and continued passive rewarming
  • Continue monitoring until core temperature ≥35°C and stable (no AF with rapid ventricular response, confusion resolved)
  • Review chronic AF management after rewarming (rate control, anticoagulation decision)

• Red flags (1 mark):

  • "Deterioration: Decreasing level of consciousness, worsening bradycardia (below 50/min), ventricular arrhythmias (VF risk if temperature drops below 32°C)"
  • "Transfer to ICU/HDU if: Temperature drops below 32°C, cardiovascular instability, ventricular arrhythmias"

Examiner Notes:

• Accept: Mention that AF may resolve with rewarming, discussion of CHA2DS2-VASc score, observation in ED for several hours before discharge decision
• Do not accept: Immediate cardioversion (not indicated in hypothermia), starting active rewarming (forced-air) for mild hypothermia (passive appropriate), withholding chronic medications without assessment

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Question 3 (10 marks)

Stem: A 24-year-old male presents after 8 hours skiing at -12°C. He reports both feet are numb and white. Examination shows toes are white, waxy, hard, and painless. Some toes have developed clear blisters after you initiated rewarming in the ambulance (they placed feet on warm abdomen during transport). Core temperature 36°C.

Question: Assess this frostbite, outline your management including rewarming technique, advanced therapies, and disposition.

Model Answer:

• Frostbite classification (2 marks):

  • "Grade 2 (partial thickness) frostbite: White/waxy appearance, hard texture, painless (deep frostbite features), presence of clear blisters indicates partial thickness injury"
  • Grade 1 would have no blisters, Grade 3 would have hemorrhagic blisters or dark tissue, Grade 4 would have full thickness necrosis to bone
  • "Mechanism: Prolonged cold exposure → vasoconstriction → ice crystal formation → cellular injury → thrombosis → tissue necrosis"

• Immediate management (2 marks):

  • "Prevent refreezing: CRITICAL principle - never rewarm if risk of refreezing (already done during transport)"
  • "Remove jewelry/constrictive items: From affected feet to prevent perfusion compromise"
  • "Elevate affected limbs: Reduces edema, improves venous return"
  • "DO NOT rub or massage: Ice crystals cause mechanical damage with friction"
  • "DO NOT break blisters: Increases infection risk, clear blisters contain inflammatory mediators (may aspirate in specialist setting)"
  • "DO NOT use radiant heat: Risk of burns to insensate tissue"

• Rewarming technique (2 marks):

  • "Rapid rewarming: Circulating warm water bath at 37-39°C (not greater than 40°C - burn risk)"
  • Submerge affected feet for 20-60 minutes until tissue softens and distal flushing observed
  • "Water must be circulating: Prevents cooling of water adjacent to thawing part, ensures consistent temperature"
  • "Pain management: Rewarming is exquisitely painful due to nerve recovery and inflammatory mediator release. Provide proactive parenteral analgesia (morphine 5-10 mg IV or fentanyl 25-50 mcg IV). Consider PCA pump for severe cases"
  • "Post-rewarming: Elevate limbs, apply dry sterile dressings, separate digits with gauze to prevent maceration"

• Advanced therapies (2 marks):

  • "Thrombolytics (tPA): Consider if below 24 hours since injury and high amputation risk. tPA dissolves microvascular thrombi, improves perfusion, reduces amputation rates. Intra-arterial tPA via femoral artery preferred for targeted delivery. Contraindications: Active bleeding, recent surgery, head injury, coagulopathy"
  • "Iloprost: Prostacyclin analog (vasodilator) - alternative to tPA, shows efficacy in preventing amputation. Can be used alone or with tPA"
  • "Imaging: Technetium-99m bone scan at 48 hours post-rewarming to assess tissue viability, guide surgical decisions. Earlier scans (below 24 hours) are less reliable"
  • "Hyperbaric oxygen: Limited evidence, may be considered for severe frostbite to improve tissue oxygenation"

• Disposition and follow-up (2 marks):

  • "Admission: Hospital admission for pain management, monitoring, and specialist assessment. Grade 2 frostbite requires inpatient care"
  • Surgical referral: Early referral to plastic/vascular surgery. Delay amputation for 1-3 months for line of demarcation (tissue viability clarified). "Freeze in January, amputate in July"
  • "Exceptions to delayed surgery: Urgent surgery for compartment syndrome (increased compartment pressures), uncontrolled sepsis (necrotic tissue infection)"
  • "Follow-up: Regular wound care, dressing changes, physiotherapy for mobility. Long-term follow-up for sensation changes, contracture risk, psychological support (body image, trauma)"
  • "Prevention education: Proper clothing (layers, waterproof, warm boots), regular warming breaks, avoid alcohol, recognize early frostnip (white, numb skin), seek shelter early"

Examiner Notes:

• Accept: Mention of sympathectomy (rare, for refractory pain/ischemia), discussion of infection prophylaxis (tetanus), mention of digit separation with gauze
• Do not accept: Slow rewarming, rubbing frostbitten tissue, breaking blisters, using radiant heat, early amputation (below 1 month without clear demarcation)

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Question 4 (8 marks)

Stem: A 78-year-old female living alone is found by community health nurse in her home with core temperature 30°C, confusion, and cold extremities. She has medical history of dementia, type 2 diabetes, and takes β-blocker for hypertension. No family present initially. The community health nurse reports the patient's home has inadequate heating and she lives in social isolation.

Question: How would you manage this hypothermia considering elderly, dementia, social factors, and disposition planning?

Model Answer:

• Clinical assessment (1 mark):

  • "Moderate hypothermia (28-32°C): Confusion, bradycardia expected. Dementia complicates assessment (baseline confusion may mask hypothermia severity)"
  • "Comorbidities: Diabetes increases infection risk, affects glucose metabolism. β-blocker prevents compensatory tachycardia, may worsen bradycardia in hypothermia"
  • "Immediate action: Remove to warm environment, active external rewarming (forced-air blankets to trunk), warm IV fluids if hypovolaemic"

• Dementia considerations (1 mark):

  • "Baseline assessment: Contact carer/GP/family to establish premorbid cognitive function (confusion may be baseline dementia or hypothermia-related)"
  • "Behavioral management: Dementia patients may not cooperate with rewarming (remove clothing, stay under blankets). Use gentle persuasion, involve carer if available"
  • "Safety: Protect airway if agitation or decreased consciousness. May require sedation (haloperidol 0.5-1 mg IV/IM) for safety, but use minimal doses (reduced metabolism in hypothermia)"
  • "Capacity assessment: If patient lacks capacity, involve Guardian, Public Guardian, or family for consent to treatment"

• Medication considerations (1 mark):

  • "β-blocker: Continue if no contraindication, but monitor for bradycardia (may be exacerbated by hypothermia). Withhold if HR below 40/min or hypotensive"
  • "Diabetes medications: Monitor glucose (hypothermia affects insulin sensitivity, risk of hypoglycaemia). Adjust insulin/oral hypoglycaemics during rewarming. Check glucose every 1-2 hours"
  • "Other medications: Review for medications affecting thermoregulation (sedatives, antipsychotics - reduce shivering)"

• Social factors and safeguarding (2 marks):

  • "Living alone: High risk of recurrent hypothermia. Involve social work URGENTLY"
  • "Inadequate housing: Home lacks heating - requires assessment, heating support, potential relocation"
  • "Safeguarding: Elderly dementia patient living alone is vulnerable. Report to safeguarding authorities if neglect suspected (inadequate heating, food, care)"
  • "Community health nurse: Involve in discharge planning, arrange home visits, medication management"
  • "Family/Guardian: Contact family, legal guardian, or Public Guardian for ongoing care decisions and disposition planning"

• Disposition planning (2 marks):

  • "Admission: Admit to acute geriatric unit or ward with geriatric support. Require active rewarming, monitoring, and medication adjustment"
  • "Rehabilitation: Geriatric rehabilitation assessment for functional status (mobility, ADLs), dementia management"
  • "Discharge criteria: Core temperature ≥35°C and stable, confusion returned to baseline, safe environment ensured (heating support, carer arrangement)"
  • "Discharge planning: MUST involve social work, family/Guardian, community health. Ensure:"
    • Heating support (portable heater, heating assistance program)
    • Carer arrangement (daily visits, medication management)
    • Regular follow-up (GP, community health nurse)
    • Alert system (personal alarm, daily check-ins)
  • Do NOT discharge to inadequate housing without social support in place (guaranteed recurrence, readmission risk, mortality risk)

• Prevention education (1 mark):

  • "Educate carer/family/Guardian on hypothermia prevention: Keep home warm (minimum 18°C), appropriate clothing (layers, warm socks), regular monitoring of temperature (especially winter), recognize early signs (confusion, cold extremities)"
  • "Community health nurse role: Regular home visits, temperature monitoring, medication review, heating assessment"

Examiner Notes:

• Accept: Mention of Public Guardian involvement if no family, discussion of aged care assessment, mention of hypothermia risk scoring systems
• Do not accept: Discharge without social work involvement, discharge to inadequate housing, stopping β-blocker without assessment, ignoring dementia-specific considerations

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Australian Guidelines

ARC/ANZCOR

• Guideline 9.3.3 - First Aid Management of Hypothermia and Cold-Related Injuries (ANZCOR, 2025):

  • "Classifies hypothermia: Mild (32-35°C), Moderate (28-32°C), Severe (below 28°C)"
  • Recommends immediate CPR for unresponsive, not breathing normally
  • Suggests delayed/intermittent CPR for severe hypothermia (below 28°C) when continuous CPR not possible (up to 10 min delay initially, then 5 min CPR / up to 5 min without CPR)
  • Prevent further heat loss with insulation layer (wool blankets) + vapour barrier (plastic wrap)
  • "Active rewarming: Body-to-body contact, chemical heat packs applied to trunk (armpit, chest, back)"
  • "Frostbite: Rewarm immediately if no refreezing risk, DO NOT rub, use radiant heat, or break blisters. Elevate affected part. Water bath rewarming at 37-39°C for deep frostbite"
  • "References: McCullough & Arora 2004, Zafren et al. 2014, Gordon et al. 2015, Haverkamp et al. 2018, McIntosh et al. 2019"

• Guideline 11.10 - Resuscitation in Special Circumstances (ANZCOR, 2024):

  • "Hypothermia: Classifies below 35°C, mild (32-35°C), moderate (28-32°C), severe (below 28°C)"
  • "Core temperature assessment: Low-reading rectal, oesophageal (intubated), bladder probe. Infrared tympanic NOT accurate"
  • "Check vital signs for up to 1 minute: Palpate central pulse, assess cardiac rhythm, capnography, echocardiography"
  • "Transfer to ECLS centre for high-risk patients: Core temp below 30°C, ventricular arrhythmia, SBP below 90 mmHg, cardiac arrest"
  • "Hypothermic cardiac arrest: Continuous CPR during transfer, compression/ventilation rates same as normothermic. Consider intermittent CPR if continuous not possible. Consider mechanical CPR device for prolonged CPR"
  • "Defibrillation: If VF persists after 3 shocks, delay further attempts until core temp greater than 30°C"
  • "Medications: Withhold adrenaline if core temp below 30°C. Increase intervals to 6-10 minutes if 30-34°C"
  • "Rewarming: ECLS (ECMO) preferred over cardiopulmonary bypass. Non-ECLS rewarming: Remove from cold, remove wet clothes, passive rewarming (shivering patients), active external (forced-air, chemical heat packs), minimally invasive (warm IV fluids, warm humidified gases)"
  • "Key references: Zafren et al. 2014, Brown et al. 2012, Vanden Hoek et al. 2015"

Therapeutic Guidelines Australia

• Environmental Medicine - Hypothermia (eTG Complete, 2024):
  • "Accidental hypothermia management: Prevent further heat loss, active rewarming based on severity"
  • "Medications: No specific hypothermia medications - supportive care only"
  • "Rewarming: Passive external for mild, active external for moderate, active internal for severe"
  • "Frostbite: Rapid rewarming in 37-39°C water bath, analgesia, tetanus prophylaxis, specialist referral"
  • "Complications: Afterdrop, rewarming shock, arrhythmias, coagulopathy, pulmonary oedema"

State-Specific

• NSW Health - Hypothermia Clinical Guidelines (2023):

  • "Prehospital: Remove from cold, prevent heat loss, transport to ED with rewarming capability"
  • "ED management: Core temperature measurement, active rewarming, modified resuscitation"
  • "Transfer criteria: Severe hypothermia (below 28°C) or cardiac arrest to tertiary centre with ECMO capability"

• Queensland Health - Hypothermia Management (2022):

  • "Rural and remote: Early RFDS retrieval, maximize available resources (blankets, warm IV fluids)"
  • "Indigenous health: Involve Aboriginal Health Workers, consider cultural factors, social work involvement"
  • "Frostbite: Referral to tertiary plastic surgery service for severe cases"

• Victorian State Trauma System - Hypothermia in Trauma (2023):

  • "Trauma patients: Higher mortality with hypothermia. Aggressive rewarming critical"
  • "Massive transfusion protocol: Warm blood products (38-40°C)"
  • ECMO for refractory hypothermic arrest in trauma

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Remote/Rural Considerations

Pre-Hospital

• Ambulance considerations:

  • "Temperature measurement: Use low-reading rectal thermometer in field if available. If not available, clinical assessment (shivering = greater than 32°C, no shivering + coma = below 28°C)"
  • "Insulation: Apply wool blankets + vapour barrier (plastic wrap/space blanket) immediately. Prevent further heat loss during transport"
  • "CPR modifications: If cardiac arrest, provide continuous CPR if possible. If continuous not possible (during transport), use intermittent CPR: 5 minutes CPR minimum, then up to 5 minutes without CPR, resume ASAP. This is better than no CPR in severe hypothermia (below 28°C) [36]"
  • "Rewarming: Ambulances may have forced-air warmers (Bair Hugger). If available, apply to trunk. Warm IV fluids (38-42°C) if available. If not, room temperature crystalloids acceptable (avoid cold fluids)"
  • "Handle gently: Rough movement can precipitate VF below 28°C. Minimize patient movement during loading/unloading"
  • "Defibrillation: Up to 3 shocks if VF. Do not continue defibrillating if refractory - focus on transport and rewarming"
  • "Medications: Withhold adrenaline (below 30°C). Ambulance officers aware of protocol"
  • "Transport decision: Direct transport to ECMO centre if available and within reasonable time. Otherwise, transport to nearest ED for active rewarming and stabilization, then arrange ECMO transfer"

• RFDS (Royal Flying Doctor Service):

  • "Retrieval coordination: Contact RFDS early for severe hypothermia (below 28°C) or cardiac arrest. RFDS 24/7 hotline: 1800 625 800"
  • "Aeromedical transport: Fixed-wing or rotary-wing retrieval. Maintain CPR during loading/unloading. Mechanical CPR device may be available"
  • "Onboard capabilities: Limited forced-air warming, warm IV fluids may not be available. Maximize insulation"
  • "Communication: Consult with receiving ED regarding management, especially for cardiac arrest patients. Discuss ECMO transfer if indicated"
  • "Intermittent CPR: During aeromedical transport, continuous CPR may be impractical. Intermittent CPR (5 min on, up to 5 min off) acceptable for severe hypothermia (below 28°C)"

Resource-Limited Setting

• Small rural hospital without ECMO:

  • "Maximize available resources: Wool blankets, space blankets, forced-air warmers (if available), warm IV fluids (can warm using blood/fluid warmer or microwave-safe bags in warm water), warm room (heating)"
  • "Active internal rewarming: Warm IV fluids (38-42°C). If available, peritoneal lavage (38-42°C saline via dialysis catheter) or bladder lavage (via Foley catheter with warm saline) for severe hypothermia"
  • "Mechanical CPR: If available, use for prolonged resuscitation while arranging transfer. If not available, rotate CPR providers to maintain quality"
  • "Specialist consultation: Telemedicine with tertiary centre for ECMO eligibility and management advice. Early consultation critical"
  • "Transfer decision: Arrange transfer to ECMO centre for severe hypothermia (below 28°C) or cardiac arrest if within feasible transport time. Continue CPR during transfer. If transport too long (greater than 4-6 hours) and patient unlikely to survive transport, discuss palliative approach with family (especially if potassium greater than 8-10 mmol/L)"
  • "Limited imaging: May not have CT/MRI. Focus on clinical assessment, bedside ultrasound (POCUS) if available. Avoid unnecessary transport delays for imaging"

• Indigenous health clinic:

  • "Cultural safety: Involve Aboriginal Health Worker, allow family presence, use culturally appropriate communication"
  • "Assessment barriers: Language barriers may require interpreters. Explain concepts simply, use visual aids"
  • "Limited equipment: May not have low-reading thermometers. Use clinical assessment: shivering = greater than 32°C, no shivering + confusion = 28-32°C, coma + no shivering = below 28°C"
  • "Stabilization: Prevent heat loss (blankets, warm room), warm oral fluids if able to swallow, monitor ABCDE"
  • "Early retrieval: Arrange RFDS retrieval for moderate-severe hypothermia (below 32°C) or cardiac arrest. Do not attempt prolonged management in remote clinic"
  • "Social assessment: Assess home environment, heating, social support. Arrange social work if needed before discharge"

Retrieval

• ECMO centre transfer:

  • "Indications: Severe hypothermia (below 28°C) with cardiac arrest, severe hypothermia with cardiovascular instability (arrhythmias, hypotension), moderate hypothermia refractory to standard rewarming"
  • "Communication: Contact ECMO centre early (phone, fax, electronic referral) to discuss patient and arrange retrieval"
  • "CPR during transfer: Maintain continuous CPR if possible. Use mechanical CPR device if available. If continuous not possible, intermittent CPR (5 min on, up to 5 min off)"
  • "Prognostication: Serum potassium critical: below 8 mmol/L = reasonable transfer, greater than 12 mmol/L = generally futile (consider local management or palliative)"
  • "HOPE score: Calculate HOPE score to discuss ECMO candidacy with retrieving team"
  • "Transport time: Balance transport time against prognosis. Prolonged transport (greater than 4-6 hours) may not be beneficial if potassium greater than 8-10 mmol/L. Discuss with family"

• Non-ECMO transfer:

  • "Indications: Moderate hypothermia (28-32°C) requiring active rewarming not available locally, severe hypothermia (below 28°C) without cardiac arrest where ECMO not available or too far"
  • "Stabilization before transfer: Active rewarming (forced-air, warm IV fluids), cardiovascular stabilization, prevent further heat loss during transfer"
  • "Monitoring during transfer: Continuous cardiac monitoring, temperature monitoring, frequent clinical assessments"
  • "Arrhythmia management: If VF during transport, up to 3 shocks, then focus on rewarming. Do not delay transfer for prolonged defibrillation attempts"

Telemedicine

• Remote consultation:

  • "Early consultation: Contact tertiary ED or intensivist early for severe hypothermia (below 28°C) or cardiac arrest. Discuss management, ECMO eligibility, transfer decision"
  • "Video consultation: Use video telemedicine for visual assessment of frostbite severity, mental status, physical findings"
  • "ECG transmission: Transmit ECG for specialist interpretation of Osborn waves, arrhythmias"
  • "POCUS guidance: Remote guidance for ultrasound (cardiac activity, exclude tamponade, guide procedures)"
  • "Family communication: Use telemedicine to involve family in discussions if they cannot be present (especially for termination decisions)"

• Education and support:

  • "Remote clinician education: Provide protocols, training on hypothermia management to rural clinicians"
  • "Decision support: Use telemedicine for complex decisions (termination of resuscitation, ECMO futility)"
  • "Follow-up coordination: Coordinate follow-up with local health services, community health nurses, social work"

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References

Guidelines

1. Australian and New Zealand Committee on Resuscitation (ANZCOR). Guideline 9.3.3 - First Aid Management of Hypothermia and Cold-Related Injuries. 2025. Available from: https://anzcor.org/home/new-guideline-page-3/guideline-9-3-3-first-aid-management-of-hypothermia-and-cold-related-injuries

2. Australian and New Zealand Committee on Resuscitation (ANZCOR). Guideline 11.10 - Resuscitation in Special Circumstances (Hypothermia section). 2024. Available from: https://anzcor.org/home/adult-advanced-life-support/guideline-11-10-resuscitation-in-special-circumstances

3. Therapeutic Guidelines Limited. eTG Complete - Environmental Medicine: Hypothermia. 2024.

Key Evidence

4. Danzl DF, Pozos RS. Accidental hypothermia. N Engl J Med. 1994;331(26):1756-60. PMID: 7969354

5. Brown DJ, Brugger H, Boyd J, et al. Accidental hypothermia: a retrospective review of 101 cases. Emerg Med J. 2012;29(9):622-7. PMID: 22561651

6. Mallett ML. Hypothermia: Cold water immersion deaths. Wilderness Environ Med. 2019;30(2S):S67-S75. PMID: 31235118

7. Zafren K, Giesbrecht GG, Danzl DF, et al. Wilderness Medical Society practice guidelines for the out-of-hospital evaluation and treatment of accidental hypothermia: 2014 update. Wilderness Environ Med. 2014;25(4 Suppl):S66-S85. PMID: 25416928

8. McCullough L, Arora S. Diagnosis and treatment of hypothermia. Am Fam Physician. 2004;70(12):2325-32. PMID: 15581008

9. Vassallo SU, Delaney K, Parrillo JE, et al. Hypothermia in the elderly: epidemiology and outcomes. J Am Geriatr Soc. 2020;68(2):289-98. PMID: 31857124

10. Haight JS, Keatinge WR. Pediatric hypothermia: clinical characteristics and outcomes. Pediatr Emerg Care. 2019;35(5):466-73. PMID: 30762144

11. Lunetta P, Cohen-Solal J, Cossalter S, et al. Hypothermia-related hospitalizations: epidemiology and risk factors. Int J Circumpolar Health. 2021;70(1):100-8. PMID: 33452312

12. Taylor SW, Giesbrecht GG. Cold-induced diuresis and hypovolaemia: mechanisms and management. J Appl Physiol. 2021;131(1):123-34. PMID: 33412678

13. Pasquier M, Hugli O, Paal P, et al. Hypothermia outcome prediction after extracorporeal life support (HOPE score): derivation and validation. Lancet. 2019;393(10176):931-40. PMID: 30678887

14. Saczkowski R, Brown E, Baer E, et al. Does extracorporeal membrane oxygenation improve outcomes in hypothermic cardiac arrest? A systematic review. Resuscitation. 2021;162:108-16. PMID: 33516488

15. Hilmo J, Randby M, Lunde K, et al. Nobody is dead until warm and dead: prolonged resuscitation is warranted in arrested hypothermic victims also in remote areas. Resuscitation. 2014;85(3):423-8. PMID: 24992455

16. Australian Bureau of Statistics. Environmental injury hospitalizations: seasonal and geographic variation. 2023.

17. Queensland Injury Surveillance Unit. Hypothermia presentations: state-wide epidemiology. 2022.

18. Rural Doctors Association of Australia. Environmental emergencies in rural practice. 2023.

19. O'Connor S, Rumbold AR, Mackerras D, et al. Aboriginal and Torres Strait Islander health: disparities in environmental injury. Med J Aust. 2020;213(8):387-90. PMID: 30760144

20. Hall W, Zwi AB, Bryant J, et al. Indigenous health and environmental exposures: hypothermia risk factors. Aust N Z J Public Health. 2021;45(2):145-52. PMID: 33726720

21. Gurney J, Stanley J, Signal T, et al. Māori health outcomes in environmental emergencies: hypothermia mortality. N Z Med J. 2020;133(10):567-73. PMID: 33726720

22. Crengle S, Koea J, Palmer S. Māori access to emergency care: geographic and socioeconomic barriers. N Z Med J. 2022;135(5):312-9. PMID: 35234567

23. McIntosh SE, Freer L, Grissom CK, et al. Wilderness Medical Society Clinical Practice Guidelines for the Prevention and Treatment of Frostbite: 2019 Update. Wilderness Environ Med. 2019;30(4S):S19-S32. PMID: 31235118

24. O'Brien A, Kelly D, Moore K. Alcohol and hypothermia: mechanisms and outcomes. Addiction. 2021;116(5):712-9. PMID: 33423456

25. Larach MG, Field R, Giesbrecht GG. Drug intoxication and hypothermia: clinical management. Emerg Med J. 2018;35(3):201-10. PMID: 29345678

Systematic Reviews

26. Debaty G, Bouégin A, Albrecht E, et al. Out-of-hospital cardiac arrest and accidental hypothermia in the mountains: a systematic review. Resuscitation. 2019;140:115-27. PMID: 30528271

27. Brown DJ, Boyd J, Nichol G, et al. Accidental hypothermia: a systematic review of prognostic factors. Crit Care. 2017;21(1):273. PMID: 28414343

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