Hyperthermia Emergency (Heat Illness)

Quick Answer

One-liner: Hyperthermia emergency encompasses heat exhaustion (core temp 38-40°C, rapid recovery) and heat stroke (core temp greater than 40°C with CNS dysfunction, mortality 10-50%), requiring immediate recognition and active cooling to prevent multi-organ failure.

30-second summary: Hyperthermia emergency ranges from heat exhaustion (core temperature 38-40°C, headache, nausea, tachycardia, rapid recovery with cooling and fluids) to heat stroke (core temperature greater than 40°C with CNS dysfunction - confusion, seizures, coma - mortality 10-50%). Heat stroke is classified as classic (non-exertional, hot dry skin, elderly/comorbid) or exertional (young healthy athletes, profuse sweating, rhabdomyolysis). Immediate management: Stop activity, active cooling (evaporative for classic, ice water immersion 1-3°C for exertional), fluid resuscitation (isotonic crystalloids), and monitor for complications (rhabdomyolysis, DIC, renal failure, hepatic failure). Cooling rate of 0.15-0.35°C/min is target. Cooling stops at core temperature 38.5-39°C. Shivering should be prevented with benzodiazepines if using evaporative cooling. Mortality for heat stroke approaches 50% without treatment, 10-20% with aggressive cooling. Australia's increasing heatwaves make heat illness a public health emergency, with elderly, children, athletes, and outdoor workers at highest risk. Indigenous and Māori populations face disproportionate burden due to housing, comorbidities, and rural/remote living conditions.

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ACEM Exam Focus

Primary Exam Relevance

• Anatomy: Thermoregulatory hypothalamus, sweat gland distribution, cutaneous blood flow, brown adipose tissue (paediatrics)
• Physiology: Thermoregulation (heat production vs heat dissipation), heat loss mechanisms (radiation, conduction, convection, evaporation), sweating threshold, cutaneous vasodilation, renal sodium conservation in heat stress
• Pharmacology: Medications impairing thermoregulation (anticholinergics, diuretics, beta-blockers, antipsychotics), dantrolene (only for malignant hyperthermia, NOT heat stroke), benzodiazepines (shivering prophylaxis)

Fellowship Exam Relevance

• Written: Heat exhaustion vs heat stroke differentiation, cooling methods (evaporative vs ice water immersion), complications (rhabdomyolysis, DIC, multi-organ failure), heatwave epidemiology, sport/workplace heat safety guidelines, Bouchama's heat stroke definition, classic vs exertional heat stroke
• OSCE: Resuscitation station (heat stroke management), Communication station (heat illness prevention education), Clinical reasoning (atypical hyperthermia presentation)
• Key domains tested: Medical Expert (rapid recognition, cooling techniques, complication management), Collaborator (team coordination for cooling, ICU handover), Professional (sport/workplace safety advocacy, public health messaging), Cultural Competence (Indigenous/Māori health considerations)

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Key Points

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Epidemiology

Australian/NZ Specific

• Heatwave excess mortality: 2009 Victoria heatwave: 374 excess deaths (+234%) over 3 days [10]
• 2019-20 Black Summer bushfires: Extreme heat conditions contributed to 445 excess deaths [11]
• Sydney 2011 heatwave: Heat-related emergency presentations increased 3-fold [12]
• Climate change projections: By 2050, heatwave days projected to increase 2-4× in Australian cities, increasing heat illness burden [13]
• Sport-related heat illness: Australian Rules Football, cricket, rugby league have highest incidence. 2014 Australian Open tennis: 960 spectators treated for heat illness, players forced to retire due to extreme conditions [14]
• Workplace heat illness: Construction, mining, agricultural workers highest risk. Outdoor workers have 3-4× higher heat-related mortality [15]

Indigenous Population Considerations:

• Aboriginal and Torres Strait Islander peoples have 2-3× higher heat-related mortality compared to non-Indigenous Australians [16]
• Contributing factors: Higher prevalence of comorbidities (diabetes, cardiovascular disease), substandard housing (lack of air conditioning, poor ventilation), geographic isolation (remote communities with limited cooling resources), socioeconomic disadvantage, chronic disease burden [17]
• Māori population (NZ) also experiences 1.5-2× higher heat-related hospitalization rates [18]

Rural/Remote Considerations:

• Heatwave impact exacerbated in rural/remote communities due to limited access to cooling facilities, delayed medical care, limited health workforce, and older housing stock [19]
• RFDS reports 40-60% increase in retrievals for heat-related illness during extreme heat events [20]

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Pathophysiology

Mechanism

Hyperthermia results from failure of thermoregulatory homeostasis when heat production exceeds heat dissipation. Normal thermoregulation maintains core temperature at 37°C ± 0.5°C through hypothalamic control center balancing:

Heat Production Sources:

• Basal metabolic rate (BMR)
• Physical activity/exercise (can increase 10-20× resting metabolism)
• Fever (infectious/inflammatory)
• Medications (stimulants, antipsychotics, thyroid hormones)
• Environmental heat gain

Heat Dissipation Mechanisms:

1. Radiation (60% at rest): Infrared emission from skin to cooler environment. Dependent on temperature gradient.
2. Convection (15% at rest): Air movement across skin removes heat. Enhanced by fans, wind.
3. Conduction (3% at rest): Direct contact with cooler objects (water, cold packs).
4. Evaporation (22% at rest, greater than 100% during exercise): Sweat evaporation from skin surface, panting (animals). Most effective in humid conditions when combined with forced air.

Pathophysiological Progression

Heat Stress → Compensated Thermoregulation → Decompensated Hyperthermia → Multi-Organ Failure

Stage 1: Heat Stress (Compensated)

• Increased cardiac output, cutaneous vasodilation, sweating
• Core temperature 37-38°C
• Physiological responses maintain homeostasis
• Symptoms: Thirst, mild fatigue, increased heart rate

Stage 2: Heat Exhaustion (Early Decompensation)

• Fluid and electrolyte depletion (sweating 1-2 L/hour during heavy exercise)
• Cardiovascular strain (tachycardia, relative hypotension)
• Core temperature 38-40°C
• Symptoms: Headache, nausea, vomiting, dizziness, muscle cramps, weakness
• Reversible with cooling and fluid replacement

Stage 3: Heat Stroke (Severe Decompensation)

• Thermoregulatory failure (sweating stops in classic heat stroke)
• Direct thermal injury to cells (protein denaturation, membrane dysfunction)
• Systemic inflammatory response syndrome (SIRS)
• Core temperature greater than 40°C with CNS dysfunction
• Medical emergency - irreversible injury without rapid cooling

Stage 4: Multi-Organ Failure

• Cardiovascular collapse (myocardial depression, arrhythmias)
• CNS injury (cerebral edema, seizures, coma)
• Hepatic necrosis (transaminases greater than 1,000 IU/L)
• Acute kidney injury (ATN from hypoperfusion, rhabdomyolysis)
• DIC (coagulopathy, bleeding)
• ARDS (pulmonary edema)
• Mortality 10-50% even with treatment

Why It Matters Clinically

The core temperature greater than 40°C threshold is critical because above this temperature:

• Protein denaturation occurs (greater than 42°C)
• Cellular membranes lose integrity
• Enzyme systems fail
• Mitochondrial dysfunction leads to ATP depletion
• Direct cytotoxic injury causes apoptosis/necrosis

Cooling must be rapid (below 30 minutes to reach below 40°C) because:

• Thermal injury is time-dependent
• Inflammatory cascade is self-perpetuating (SIRS, cytokine storm)
• Cellular damage becomes irreversible after 60-90 minutes of severe hyperthermia
• Early cooling (within 30 minutes) reduces mortality from 50% to 10-20%

Classic vs Exertional Heat Stroke Pathophysiology

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Clinical Approach

Recognition

Heat Exhaustion Recognition Features:

• Core temperature 38-40°C
• Headache, dizziness, nausea, vomiting
• Tachycardia (HR 100-140 bpm)
• Hypotension (SBP 90-100 mmHg, orthostatic)
• Sweating present (profuse)
• Mild confusion (normal GCS 14-15)
• Muscle cramps, weakness
• Thirst, fatigue

Heat Stroke Recognition Features:

• Core temperature greater than 40°C (mandatory diagnostic criterion)
• CNS dysfunction (mandatory diagnostic criterion):
  • Confusion, disorientation, agitation
  • Delirium, seizures, coma
  • Ataxia, dysarthria
• Skin findings:
  • "Classic: Hot, dry skin (anhidrosis) - 50-60% of cases"
  • "Exertional: Profuse sweating - 40-50% of cases"
  • Anhidrosis is NOT universal
• Cardiovascular: Tachycardia (greater than 140 bpm), hypotension (SBP below 90 mmHg), arrhythmias
• Gastrointestinal: Nausea, vomiting, diarrhea, hepatic tenderness
• Musculoskeletal: Muscle cramps, weakness, rhabdomyolysis (dark urine)
• Respiratory: Tachypnea, ARDS (severe cases)
• Renal: Oliguria, anuria, AKI

Bouchama Heat Stroke Definition (Diagnostic Criteria):

1. Core temperature greater than 40°C
2. CNS dysfunction (altered mental status, seizures, coma)
3. Hot, dry skin OR profuse sweating
4. Exclusion of other causes of hyperthermia (sepsis, thyroid storm, malignant hyperthermia, NMS, serotonin syndrome)

Initial Assessment

Primary Survey (Critical Patients)

• A: Airway protection if GCS below 8, seizure prophylaxis (benzodiazepines)
• B: Oxygenation (SpO2 94-98%), ventilatory support if respiratory distress
• C: Circulatory assessment (BP, HR, peripheral perfusion), IV access (2 large-bore)
• D: GCS assessment (focus on CNS dysfunction), pupil examination, check for seizures
• E: Core temperature (rectal, esophageal, or bladder probe), skin assessment (dry vs sweating), check for signs of trauma (exertional collapse), remove clothing to facilitate cooling

History

Key Questions

Red Flag Symptoms

Examination

General Inspection

• Level of consciousness (GCS), agitation, delirium, coma
• Skin: Hot to touch, dry (anhidrosis) vs sweating, color (flushed vs cyanotic)
• Diaphoresis: Profuse sweating (exertional) vs absent (classic)
• Muscle tone: Normal vs rigid (rhabdomyolysis, seizures)
• Signs of trauma: Fall injuries from exertional collapse

Specific Findings

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Investigations

Immediate (Resus Bay)

Standard ED Workup

Advanced/Specialist

Point-of-Care Ultrasound

POCUS applications for hyperthermia:

• Cardiac: Assess global systolic function, rule out wall motion abnormalities (myocardial injury), volume status (IVC collapsibility)
• Lung: Assess for pulmonary edema (B-lines), pneumothorax (in trauma from collapse)
• Abdominal: Gallbladder wall thickening (hypovolemia), free fluid (unlikely in heat stroke but rule out trauma)
• Focused Assessment with Sonography in Trauma (FAST): If fall or collapse with trauma
• Procedural guidance: IV access, bladder catheterization

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Management

Immediate Management (First 10 minutes)

1. STOP ACTIVITY immediately and move to cool/shaded environment
2. REMOVE clothing to facilitate heat loss
3. MEASURE core temperature (rectal, esophageal, or bladder probe)
4. START ACTIVE COOLING immediately if core temp greater than 40°C
5. OBTAIN IV access (2 large-bore lines, 16-18G)
6. ADMINISTER isotonic crystalloids (Normal saline or Hartmann's) 500-1000 mL bolus
7. MONITOR ECG, SpO2, BP, temperature continuously
8. TREAT seizures (benzodiazepines: diazepam 5-10 mg IV or lorazepam 2-4 mg IV)
9. INTUBATE if GCS below 8, respiratory failure, or inability to protect airway
10. CALL FOR HELP (ICU, critical care team)

Resuscitation

Airway

• GCS ≥8: Airway patent, supplemental oxygen via nasal cannula or face mask (4-6 L/min, target SpO2 94-98%)
• GCS below 8: Rapid sequence intubation (RSI)
  • "Induction: Ketamine 1-2 mg/kg IV (hemodynamically stable, bronchodilatory) OR etomidate 0.3 mg/kg IV (hemodynamic stability)"
  • "Paralysis: Rocuronium 1.2 mg/kg IV OR succinylcholine 1-1.5 mg/kg IV (if no contraindications)"
  • "Post-intubation: Sedation (midazolam infusion), analgesia (fentanyl infusion), ventilator lung-protective strategy"

Breathing

• Oxygenation: Target SpO2 94-98%
• Ventilation (if intubated):
  • "Tidal volume: 6-8 mL/kg IBW"
  • "PEEP: 5-10 cm H2O"
  • "FiO2: Titrate to SpO2"
  • "Respiratory rate: 12-16 breaths/min"
• Non-intubated: High-flow nasal cannula or non-rebreather mask if hypoxic

Circulation

• Fluid resuscitation:
  • "Initial bolus: Normal saline or Hartmann's 500-1000 mL IV over 15-30 minutes"
  • "Ongoing: Titrate to urine output greater than 0.5 mL/kg/hr, MAP greater than 65 mmHg"
  • Avoid overhydration (risk of pulmonary edema in ARDS)
  • "Rhabdomyolysis: Aggressive fluids 200-300 mL/hr to maintain urine output 100-200 mL/hr"
• Vasopressors (if refractory hypotension despite fluids):
  • Norepinephrine 0.05-0.5 mcg/kg/min IV infusion
  • Target MAP greater than 65 mmHg
• Arrhythmias:
  • "Sinus tachycardia: Treat underlying hyperthermia (cooling, fluids)"
  • "Atrial fibrillation with RVR: Rate control (metoprolol 2.5-5 mg IV, avoid in hypotension) OR rhythm control (amiodarone 150 mg IV)"
  • "Ventricular tachycardia: Amiodarone 150 mg IV over 10 minutes, then 1 mg/min infusion for 6 hours"
  • "Pulseless VT/VF: ACLS protocol (defibrillation, epinephrine 1 mg IV q3-5 min)"

Active Cooling Methods

Cooling Priority: Rapid cooling to reduce core temperature to 38.5-39°C within 30 minutes

Cold Water Immersion (Exertional Heat Stroke)

Technique:

1. Fill tub with water at 1-3°C (ice + water mixture)
2. Immerses patient up to neck
3. Continuously stir water to prevent warm layer formation
4. Monitor core temperature continuously (rectal/esophageal probe)
5. Remove from water when core temperature reaches 38.5-39°C
6. Continue evaporative cooling if temperature rebounds

Shivering prophylaxis: If shivering impedes cooling, give:

• Diazepam 5-10 mg IV OR
• Chlorpromazine 25-50 mg IV (cautious in hypotension)

Contraindications:

• Altered mental status with inability to protect airway (risk of drowning)
• Hemodynamic instability (risk of cardiovascular collapse)
• Elderly/comorbid patients (shivering common, cardiovascular strain)

Evaporative Cooling (Classic Heat Stroke, ICU)

Technique:

1. Remove all clothing
2. Spray patient with lukewarm water (15-20°C) using spray bottles
3. Direct high-velocity fans at patient (use room fans if available)
4. Continuously mist and fan until core temperature reaches 38.5-39°C
5. Monitor core temperature continuously
6. Prevent shivering with benzodiazepines (diazepam 5-10 mg IV)

Advantages:

• Can be performed at bedside
• No risk of drowning
• Suitable for intubated/comatose patients
• Well-tolerated by elderly/comorbid patients

Enhanced evaporative cooling (for refractory cases):

• Add ice packs to axillae, groin, neck
• Cooling blankets (overlay)
• Consider intravascular cooling catheter if available

Cooling Targets

• Target temperature: 38.5-39°C
• Stop cooling when target reached
• Overcooling below 38°C is NOT recommended:
  • May induce shivering (counterproductive)
  • May cause cardiovascular instability
  • Complicates monitoring

Temperature monitoring:

• Rectal probe: Most accessible, 5-10 minute lag from core
• Esophageal probe: Most accurate, fast response, requires intubation
• Bladder probe: Accurate, requires Foley catheter with temperature sensor
• Avoid: Oral, axillary, tympanic (inaccurate for cooling monitoring)

Medications

Paediatric Dosing

Ongoing Management

After initial cooling to 38.5-39°C:

1. Continuous monitoring:

   • Core temperature (every 5 minutes until stable, then hourly)
   • ECG, SpO2, BP (continuous)
   • Urine output (hourly, target greater than 0.5-1 mL/kg/hr)
   • Neurological status (GCS hourly)

2. Laboratory monitoring:

   • FBC, U&E, CK, LFTs, coagulation (q6-12h for 24-48h)
   • Troponin (q12h if myocardial dysfunction suspected)
   • ABG/VBG (as clinically indicated)

3. Cooling:

   • Continue evaporative cooling if temperature rebounds greater than 39°C
   • Prevent shivering with benzodiazepines

4. Complication management:

   • Rhabdomyolysis: Aggressive fluids (200-300 mL/hr), alkalinise urine (sodium bicarbonate if pH below 7.1), consider dialysis if refractory AKI
   • DIC: Treat underlying cause, replace blood products (FFP, platelets, cryoprecipitate) as indicated
   • Hepatic necrosis: Supportive care, consider N-acetylcysteine (controversial), monitor for hepatic encephalopathy
   • AKI: Nephrology input, dialysis if indicated
   • ARDS: Lung-protective ventilation, consider proning, ECMO if refractory
   • Seizures: Benzodiazepines, levetiracetam loading 20 mg/kg, then 10 mg/kg q12h

Definitive Care

• ICU admission for all heat stroke patients
• Cooling: Continue monitoring, prevent temperature rebounds
• Organ support:
  • Mechanical ventilation if respiratory failure
  • Renal replacement therapy if AKI
  • Inotropic support if myocardial dysfunction
  • Vasopressors if distributive shock
• Disposition:
  • "Admission: ICU for heat stroke, ward for heat exhaustion if resolving"
  • "Discharge: Heat exhaustion with normal vitals, normal labs, reliable follow-up"
  • "Heat stroke: Minimum 48-72 hour observation, often 7-14 day hospitalization"

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Disposition

Admission Criteria

ICU Admission (Mandatory for heat stroke):

• Core temperature greater than 40°C with CNS dysfunction
• Hemodynamic instability (SBP below 90 mmHg refractory to fluids)
• Respiratory failure requiring mechanical ventilation
• Severe complications:
  • Rhabdomyolysis (CK greater than 10,000 IU/L)
  • AKI (creatinine greater than 2× baseline, oliguria)
  • DIC (coagulopathy, bleeding)
  • Hepatic necrosis (AST/ALT greater than 1,000 IU/L)
  • ARDS
• Persistent neurological abnormalities

Ward Admission:

• Heat exhaustion with ongoing symptoms
• Moderate rhabdomyolysis (CK 1,000-10,000 IU/L)
• Mild AKI (creatinine below 2× baseline)
• Requiring IV fluids but stable for ward care
• Social factors (unable to self-care at home)

ICU/HDU Criteria

Level 3 (ICU):

• Mechanical ventilation
• Vasopressor requirement
• Renal replacement therapy
• Multi-organ failure (greater than 2 organ systems)
• Refractory seizures

Level 2 (HDU):

• Single organ support
• Invasive monitoring (arterial line, CVP)
• Close observation (hourly neurological checks)
• High-dependency fluid/electrolyte management

Discharge Criteria

Heat exhaustion discharge:

• Core temperature below 38°C
• Normal mental status (GCS 15)
• Normal vital signs (SBP greater than 90 mmHg, HR below 100 bpm, RR below 20)
• Normal laboratory values (CK below 1,000 IU/L, normal creatinine, normal electrolytes)
• Able to tolerate oral fluids
• Reliable adult supervision at home
• Red flags education provided

Heat stroke discharge:

• Minimum 48-72 hour observation
• Resolution of CNS dysfunction (GCS 15)
• Resolution of complications (normal CK, normal creatinine, normal coagulation)
• Normal LFTs (AST/ALT below 100 IU/L)
• Hemodynamically stable off vasopressors
• Able to ambulate and self-care
• Heat illness prevention education provided
• Follow-up arranged with GP or specialist

Follow-up

• GP letter: Include diagnosis, management, complications, follow-up plan
• Specialist referral:
  • Nephrology (if AKI, CK greater than 1,000 IU/L)
  • Cardiology (if myocardial dysfunction, arrhythmias)
  • Neurology (if persistent neurological deficits)
  • Hepatology (if hepatic necrosis)
• Rehabilitation: Physical therapy if deconditioned, occupational therapy if functional limitations
• Heat illness prevention education:
  • Heat safety measures
  • Hydration strategies
  • Acclimatization to heat
  • Recognition of early heat illness symptoms

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Special Populations

Paediatric Considerations

Differences from adults:

• Higher surface-area-to-mass ratio → faster heat gain/loss
• Immature thermoregulatory system → less efficient sweating
• Dependence on adults for hydration and heat safety
• Higher risk of heat exhaustion/stroke in enclosed vehicles

Management modifications:

• Cooling methods: Cold water immersion preferred if safe (faster cooling), evaporative cooling alternative
• Fluid resuscitation: 10-20 mL/kg bolus, ongoing maintenance fluids
• Monitoring: More frequent neurological checks (children may compensate longer then decompensate rapidly)
• Seizure threshold: Lower in children, aggressive seizure prophylaxis
• Dosing: Weight-based medication dosing

Heat illness prevention in children:

• Never leave children unattended in vehicles (even with windows cracked)
• Adequate hydration during play
• Limit outdoor activities during peak heat (10 am - 4 pm)
• Acclimatization for sports participation

Pregnancy

Physiological changes affecting heat stress:

• Increased BMR (15-20% higher) → increased heat production
• Decreased thermoregulatory threshold → sweating starts at lower temperatures
• Increased blood volume → potential for hypervolemia, cardiac strain
• Fetal thermoregulation depends on maternal temperature

Management modifications:

• Cooling: Evaporative cooling preferred (avoid cold water immersion with supine hypotension risk)
• Fluid resuscitation: Aggressive but avoid pulmonary edema (reduced lung capacity)
• Monitoring: Fetal heart rate monitoring if viable gestation (greater than 24 weeks)
• Medications: Avoid teratogenic drugs (most cooling medications safe)
• Disposition: Obstetric consultation, consider maternal-fetal transfer to tertiary centre

Fetal considerations:

• Maternal hyperthermia greater than 38°C associated with neural tube defects (first trimester) and fetal distress (third trimester)
• Rapid maternal cooling critical for fetal protection

Elderly

Increased risk factors:

• Reduced thermoregulatory efficiency (impaired sweating, cutaneous vasodilation)
• Higher prevalence of comorbidities (cardiovascular disease, diabetes, CKD)
• Polypharmacy (anticholinergics, diuretics, beta-blockers)
• Social isolation (limited access to cooling, delayed presentation)
• Reduced thirst perception → dehydration

Management modifications:

• Cooling methods: Evaporative cooling preferred (cold water immersion poorly tolerated, shivering common, cardiovascular strain)
• Fluid resuscitation: Conservative boluses (250-500 mL), monitor for pulmonary edema
• Cardiovascular monitoring: More aggressive (elderly at risk of arrhythmias, myocardial ischemia)
• Dosing: Reduced medication doses (renal/hepatic impairment)
• Discharge: Extended observation (24-48 hours minimum for heat exhaustion)

Heat illness prevention in elderly:

• Social checks during heatwaves (neighbors, community services)
• Access to air conditioning or cooling centers
• Medication review during heat season
• Hydration reminders

Indigenous Health

Important Note: Aboriginal, Torres Strait Islander, and Māori considerations:

Health Disparities:

• Aboriginal and Torres Strait Islander peoples: 2-3× higher heat-related mortality compared to non-Indigenous Australians [16]
• Māori (NZ): 1.5-2× higher heat-related hospitalization rates [18]
• Contributing factors:
  • Higher prevalence of comorbidities (diabetes, cardiovascular disease, CKD)
  • Substandard housing (lack of air conditioning, poor ventilation, overcrowding)
  • Geographic isolation (remote communities with limited cooling resources)
  • Socioeconomic disadvantage (limited access to healthcare, delayed presentation)
  • Cultural factors (reluctance to seek care, language barriers)
  • Chronic disease burden amplifies heat vulnerability

Cultural Safety Considerations:

• Involve Aboriginal Health Workers (AHWs), Aboriginal Liaison Officers (ALOs), or Māori Health Workers early
• Use culturally appropriate communication (plain language, visual aids, family presence)
• Respect cultural protocols around health, healing, and family decision-making
• Allow extended family presence (whānau involvement for Māori)
• Consider cultural practices around cooling (e.g., traditional bush medicines alongside western medicine)

Geographic Barriers:

• Remote/remote communities: Limited access to cooling facilities, delayed medical care
• Seasonal variations: Wet season (NT) may delay retrieval
• Resource limitations: No ICU, limited ventilators, limited blood product availability
• RFDS: Early retrieval consideration for heat stroke (see Remote/Rural section)

Communication Strategies:

• Use interpreters if language barriers exist
• Avoid medical jargon, use simple explanations
• Visual aids (thermometers, pictures of cooling methods)
• Written information in plain English or translated materials
• Family/community education on heat illness prevention

Heat Illness Prevention Programs:

• Community-led heat safety education
• Cooling center access during heatwaves
• Cultural liaison for medication review (heat-predisposing medications)
• Traditional knowledge integration with western heat safety

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Pitfalls & Pearls

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Viva Practice

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OSCE Scenarios

Station 1: Resuscitation Station - Heat Stroke Management

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

Candidate Instructions:

You are the team leader in the ED. A 32-year-old male marathon runner has been brought in by ambulance. He collapsed during a race on a hot day (32°C). He is confused and profusely sweating. The paramedics report a rectal temperature of 41.5°C en route. You have a nurse and a registrar to assist you. Please manage this patient.

Examiner Instructions: The patient is a 32-year-old male with exertional heat stroke. He presents with:

• GCS 13 (confused but verbalizes)
• Core temperature (rectal probe): 41.5°C
• HR 145 bpm, BP 98/62 mmHg, RR 26/min, SpO2 97% on room air
• Skin: Hot, profusely sweating
• No evidence of trauma

The patient responds to voice but is confused. Airway is patent. Breathing is adequate. IV access: 18G in right antecubital fossa.

Expected progression:

1. Candidate recognizes heat stroke (core temp greater than 40°C + CNS dysfunction)
2. Candidate initiates active cooling immediately (cold water immersion or evaporative cooling)
3. Candidate orders fluid resuscitation (Normal saline or Hartmann's 500-1000 mL bolus)
4. Candidate orders investigations (FBC, U&E, CK, LFTs, coagulation, ABG, urinalysis)
5. Candidate monitors for complications (rhabdomyolysis, DIC, AKI)
6. Candidate arranges ICU admission

Marking Criteria:

Expected Standard:

• Pass: ≥12/19
• Key discriminators:
  • "Fail: Delays cooling for investigations or transfer, uses dantrolene, fails to recognize heat stroke"
  • "Pass: Initiates cooling immediately, uses appropriate method, orders fluids and investigations"
  • "High pass: Demonstrates knowledge of exertional vs classic heat stroke, targets cooling correctly, explains monitoring for complications (rhabdomyolysis, DIC)"

Critical Actions (Must be performed for pass):

1. Recognizes heat stroke (core temp greater than 40°C + CNS dysfunction)
2. Initiates active cooling immediately (do NOT delay for transfer)
3. Administers IV fluid bolus (500-1000 mL)
4. Orders CK (screen for rhabdomyolysis)
5. Arranges ICU admission

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Station 2: Communication Station - Heat Illness Prevention Education

Format: Communication Time: 11 minutes Setting: ED cubicle

Candidate Instructions:

You are an emergency physician. A local high school has had 3 students present to the ED with heat exhaustion over the past 2 weeks during sports training sessions in hot weather. The school principal is concerned and has asked for your advice on preventing heat illness in student athletes. You have 11 minutes to provide comprehensive heat illness prevention education.

Examiner Instructions: The school principal is concerned but not medically trained. They want practical, actionable advice for preventing heat illness in student athletes during sports training. They are open to implementing new policies and procedures.

The principal may ask:

• "How do we know when it's too hot to train outside?"
• "What should students drink during training?"
• "How can we recognize heat illness early?"
• "What should we do if a student collapses?"

Expected progression:

1. Candidate establishes rapport and acknowledges concern
2. Candidate explains heat illness spectrum (heat exhaustion vs heat stroke)
3. Candidate provides practical prevention strategies:
   • Hydration guidelines
   • Acclimatization protocols
   • Rest and cooling breaks
   • Recognizing early symptoms
   • Emergency action plan
4. Candidate addresses heat policy implementation (wet bulb globe temperature, cancellation thresholds)
5. Candidate offers resources and follow-up support

Marking Criteria:

Expected Standard:

• Pass: ≥12/19
• Key discriminators:
  • "Fail: Provides incorrect medical advice, fails to explain heat stroke urgency, no practical recommendations"
  • "Pass: Provides practical hydration and cooling advice, explains heat illness spectrum, discusses emergency action plan"
  • "High pass: Discusses WBGT monitoring, specific cancellation thresholds, acclimatization protocols, offers resources for implementation"

Critical Actions (Must be performed for pass):

1. Explains heat exhaustion vs heat stroke
2. Provides hydration guidelines (150-250 mL every 15-20 min)
3. Describes early symptoms of heat illness
4. Outlines emergency action plan (call 000, start cooling)
5. Recommends cancellation of training in extreme heat

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Station 3: Clinical Reasoning Station - Atypical Hyperthermia

Format: Clinical Reasoning Time: 11 minutes Setting: ED consultation room

Candidate Instructions:

A 42-year-old female presents with fever, confusion, and muscle rigidity. She was started on fluoxetine (SSRI) for depression 2 weeks ago and recently increased the dose. She also takes tramadol for chronic back pain. On examination: T 39.5°C, GCS 13, HR 125 bpm, BP 115/75 mmHg. She is confused and has muscle rigidity with hyperreflexia. No clear heat exposure history. Please provide your differential diagnosis and initial management plan.

Examiner Instructions: The candidate should recognize the atypical presentation (hyperthermia without heat exposure, muscle rigidity, serotonergic medications) and generate differential diagnoses.

The examiner may ask:

• "What is your differential diagnosis?"
• "What is the most likely diagnosis?"
• "How would you manage this patient?"
• "What investigations would you order?"
• "What are the complications you are concerned about?"

Expected progression:

1. Candidate generates differential diagnosis:
   • Serotonin syndrome (SSRI + tramadol)
   • Neuroleptic malignant syndrome (if on antipsychotics)
   • Heat stroke (but no heat exposure)
   • Malignant hyperthermia (no anesthesia exposure)
   • Sepsis (possible but no infectious source)
2. Candidate identifies most likely diagnosis (serotonin syndrome)
3. Candidate provides management plan:
   • Discontinue serotonergic medications
   • Benzodiazepines for agitation/muscle rigidity
   • Cooling if temperature greater than 40°C
   • Supportive care, ICU admission
4. Candidate orders investigations (CK, renal function, electrolytes, coagulation)
5. Candidate discusses complications (rhabdomyolysis, DIC, AKI)

Marking Criteria:

Expected Standard:

• Pass: ≥12/19
• Key discriminators:
  • "Fail: Misses serotonin syndrome, recommends dantrolene (wrong indication), fails to discontinue serotonergic medications"
  • "Pass: Identifies serotonin syndrome as likely diagnosis, discontinues triggering medications, recommends benzodiazepines"
  • "High pass: Clearly differentiates serotonin syndrome from NMS/MH, discusses clonus vs rigidity, knows that cyproheptadine is antidote (though rarely used in ED), discusses fluid management for rhabdomyolysis"

Critical Actions (Must be performed for pass):

1. Identifies serotonin syndrome as likely diagnosis
2. Recommends discontinuing serotonergic medications (fluoxetine, tramadol)
3. Recommends benzodiazepines for agitation/muscle rigidity
4. Orders CK (screen for rhabdomyolysis)
5. Arranges ICU admission

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SAQ Practice

Question 1 (8 marks)

Stem: A 28-year-old male marathon runner collapses at the 35 km mark during a summer race. Ambient temperature 34°C, humidity 75%. He is confused on arrival to ED. Core temperature 41.8°C, HR 150 bpm, BP 90/60 mmHg, RR 28/min, SpO2 97% on room air. Skin is hot and profusely sweating. CK is 8,500 IU/L.

Question: (a) What is the diagnosis and what are the key diagnostic criteria? (2 marks) (b) Outline your immediate management plan, including cooling method and targets. (4 marks) (c) What complications should you monitor for, and how would you manage them? (2 marks)

Model Answer:

(a) Diagnosis and diagnostic criteria (2 marks):

• Diagnosis: Exertional heat stroke (1 mark)
• Key diagnostic criteria (1 mark):
  • Core temperature greater than 40°C (41.8°C in this case)
  • CNS dysfunction (confusion)
  • Heat exposure history (summer marathon)
  • "Exertional pattern: Young athlete, profuse sweating (anhidrosis NOT universal)"

(b) Immediate management plan (4 marks):

• Active cooling immediately (1 mark):
  • Cold water immersion (1-3°C) preferred for exertional heat stroke in young athlete (1 mark)
  • Alternatively, evaporative cooling (water mist + high-velocity fans) if immersion unavailable
  • "Cooling target: Cool to 38.5-39°C, then stop cooling (do not overcool below 38°C) (1 mark)"
• Fluid resuscitation (1 mark):
  • Normal saline or Hartmann's 500-1000 mL IV bolus over 15-30 minutes
  • Ongoing fluids titrated to urine output greater than 0.5 mL/kg/hr
• Airway and breathing (0.5 mark):
  • GCS currently acceptable (greater than 8) but monitor closely
  • Supplemental oxygen if hypoxic (SpO2 94-98%)
• Monitoring (0.5 mark):
  • Continuous ECG, SpO2, BP, core temperature (rectal or esophageal probe)
• Investigations (include in management):
  • FBC, U&E, CK (already elevated 8,500 IU/L), LFTs, coagulation, ABG, urinalysis (myoglobin screen)

(c) Complications and management (2 marks):

• Rhabdomyolysis (1 mark):
  • CK 8,500 IU/L confirms rhabdomyolysis
  • "Management: Aggressive fluids 200-300 mL/hr to maintain urine output 100-200 mL/hr, alkalinise urine if pH below 7.1, consider dialysis if AKI refractory"
• Other complications to monitor (1 mark):
  • Acute kidney injury (monitor creatinine, urine output)
  • Hepatic necrosis (monitor LFTs, AST/ALT may be greater than 1,000 IU/L)
  • DIC (monitor INR, APTT, fibrinogen, platelets)
  • ARDS (monitor for pulmonary edema, respiratory distress)
  • Seizures (benzodiazepines prophylaxis)
  • Arrhythmias (ECG monitoring, electrolytes)

Examiner Notes:

• Accept: Evaporative cooling if cold water immersion not available, isotonic crystalloids (Normal saline or Hartmann's), any appropriate cooling target (38-39°C range)
• Do not accept: Dantrolene (only for malignant hyperthermia/NMS), delaying cooling for transfer, axillary/tympanic temperature for monitoring
• Full marks for: Recognition of exertional heat stroke, cold water immersion as preferred cooling, aggressive fluids for rhabdomyolysis, listing multiple complications

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Question 2 (8 marks)

Stem: A 72-year-old female is found unconscious in her non-air-conditioned apartment during a heatwave. Indoor temperature 39°C. On arrival to ED, she is comatose (GCS 3), core temperature 41.5°C, HR 158 bpm, BP 65/40 mmHg, RR 32/min, SpO2 88% on room air. Skin is hot and dry. She has a history of hypertension and type 2 diabetes.

Question: (a) What is the diagnosis and what are the key features distinguishing it from exertional heat stroke? (2 marks) (b) Outline your immediate management, including airway, breathing, circulation, and cooling. (4 marks) (c) What is the expected prognosis, and what factors influence outcome? (2 marks)

Model Answer:

(a) Diagnosis and distinguishing features (2 marks):

• Diagnosis: Classic heat stroke (1 mark)
• Distinguishing features from exertional heat stroke (1 mark):
  • Elderly patient (72 years) vs young athlete
  • Non-exertional (found in apartment) vs during exercise
  • Hot dry skin (anhidrosis) vs profuse sweating
  • Higher mortality (20-50%) vs exertional (10-20%)
  • Multi-organ failure (DIC, hepatic necrosis) more common vs rhabdomyolysis more common in exertional
  • Coma (GCS 3) vs confusion in exertional

(b) Immediate management (4 marks):

• Airway (1 mark):
  • GCS 3 → Immediate intubation required
  • "RSI: Ketamine 1 mg/kg IV (hemodynamic support preferred) or etomidate 0.3 mg/kg IV"
  • Rocuronium 1.2 mg/kg IV for paralysis
  • "Post-intubation: Midazolam infusion, fentanyl infusion"
• Breathing (1 mark):
  • "Lung-protective ventilation: TV 6-8 mL/kg IBW, PEEP 5-10 cm H2O, FiO2 titrate to SpO2 94-98%"
  • Monitor for ARDS
• Circulation (1.5 marks):
  • "Fluid resuscitation: Normal saline 500-1000 mL IV bolus (conservative due to age, monitor for pulmonary edema)"
  • "Vasopressors: Norepinephrine 0.05-0.5 mcg/kg/min IV infusion if refractory hypotension despite fluids (target MAP greater than 65 mmHg)"
  • Large-bore IV access (16-18G) × 2
• Cooling (0.5 mark):
  • Evaporative cooling preferred for elderly/comorbid (cold water immersion poorly tolerated)
  • Remove clothing, water mist + high-velocity fans
  • "Target: Cool to 38.5-39°C"

(c) Prognosis and influencing factors (2 marks):

• Expected prognosis: Guarded to poor (1 mark)
  • "Mortality for classic heat stroke with coma: 20-50%, higher (greater than 60%) with GCS below 8 and core temp greater than 41°C"
• Factors influencing outcome (1 mark):
  • "Favorable: Rapid cooling (below 30 minutes), age below 65, shorter hyperthermia duration, no pre-existing comorbidities, normal baseline functional status"
  • "Unfavorable: Prolonged hyperthermia (greater than 2 hours), core temperature greater than 42°C, comatose presentation (GCS below 8), multi-organ failure (DIC, AKI, hepatic necrosis), pre-existing cardiovascular disease (hypertension, diabetes), delayed cooling (greater than 60 minutes)"
  • "This patient: Several unfavorable factors (age 72, GCS 3, core temp 41.5°C, comorbidities), but mortality may be reduced to 30-40% with rapid cooling and aggressive ICU support"

Examiner Notes:

• Accept: Etomidate instead of ketamine for RSI, Hartmann's instead of Normal saline for fluids
• Do not accept: Cold water immersion in elderly (poorly tolerated), dantrolene, conservative fluids without monitoring for pulmonary edema
• Full marks for: Recognizing classic heat stroke, intubation for GCS below 8, evaporative cooling for elderly, appropriate fluid dosing, knowledge of prognosis factors

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Question 3 (8 marks)

Stem: You are working in a remote community clinic during a heatwave (ambient 43°C). A 50-year-old Aboriginal man presents with headache, dizziness, nausea, and fatigue for 3 days. He works outdoors as a mining labourer. On examination: T 39.2°C (tympanic), HR 120 bpm, BP 105/75 mmHg, RR 22/min, SpO2 97%, GCS 15. He is diaphoretic, appears dehydrated (dry mucous membranes). The clinic has limited resources (no ICU, no ventilator). RFDS retrieval available but 4-hour flight time.

Question: (a) What is the diagnosis, and what are the criteria distinguishing it from heat stroke? (2 marks) (b) Outline your management in this remote setting, including disposition decisions. (4 marks) (c) What are the important cultural and public health considerations for Aboriginal communities during heatwaves? (2 marks)

Model Answer:

(a) Diagnosis and distinguishing criteria (2 marks):

• Diagnosis: Heat exhaustion (1 mark)
• Distinguishing from heat stroke (1 mark):
  • Core temperature 39.2°C (below 40°C) - heat exhaustion is 38-40°C, heat stroke is greater than 40°C
  • Intact CNS (GCS 15) - heat stroke requires CNS dysfunction (confusion, seizures, coma)
  • Diaphoretic (sweating) - classic heat stroke has hot dry skin (anhidrosis) but not universal
  • Rapid recovery with cooling and fluids - heat exhaustion resolves quickly, heat stroke requires ICU and prolonged management

(b) Management in remote setting (4 marks):

• Immediate management (2 marks):
  • Stop activity and move to cool/shaded area (air-conditioned clinic)
  • "Cooling measures: Evaporative cooling (water mist + fans), remove excess clothing, cool towels to head, neck, axillae (1 mark)"
  • "Rehydration: Oral fluids if able (water, electrolyte solution). If vomiting: IV Normal saline or Hartmann's 500-1000 mL bolus, then maintenance 100-150 mL/hr (1 mark)"
  • "Medications: Antiemetic (ondansetron 4-8 mg IV) if vomiting, paracetamol 1 g for headache"
• Monitoring (1 mark):
  • Tympanic temperature q30min (rectal probe unavailable), vital signs q30min
  • GCS hourly (monitor for progression to heat stroke)
  • Urine output (catheter if needed, target greater than 0.5 mL/kg/hr)
• Disposition (1 mark):
  • If improving (core temp below 38°C, normal vitals, GCS 15, tolerating oral fluids) within 2-4 hours → Discharge with adult supervision, AHW follow-up
  • If deteriorating (core temp greater than 40°C OR GCS below 14) → Urgent RFDS retrieval to tertiary hospital with ICU (heat stroke)
  • "Contact RFDS: 24/7 retrieval hotline 1800 625 800"

(c) Cultural and public health considerations (2 marks):

• Cultural safety (1 mark):
  • Involve Aboriginal Health Worker (AHW) for cultural liaison, communication, family engagement
  • Respect cultural protocols (family decision-making, presence of elders)
  • Use plain language, visual aids, interpreter if language barriers
  • Understand social context (housing conditions, work responsibilities)
• Public health considerations (1 mark):
  • Aboriginal and Torres Strait Islander peoples have 2-3× higher heat-related mortality due to comorbidities, substandard housing, geographic isolation
  • "Prevention education: Community-led, culturally appropriate (hydration, early symptom recognition, rest breaks, cool housing)"
  • "Vulnerable groups: Check on elderly, children, people with chronic diseases during heatwaves"
  • "Resources: Cooling centers, social checks, AHW home visits, heat safety information"
  • "Climate change: Heatwaves increasing in frequency and duration, future burden on Indigenous communities"

Examiner Notes:

• Accept: Any appropriate cooling method (evaporative, cold packs), isotonic crystalloids (Normal saline or Hartmann's)
• Do not accept: Diagnosis of heat stroke (core temp below 40°C, GCS 15), discharge without observation, cold water immersion in remote clinic without monitoring
• Full marks for: Recognizing heat exhaustion, appropriate cooling and rehydration, clear disposition criteria, cultural safety involvement, public health awareness

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Question 4 (8 marks)

Stem: A 55-year-old male presents with fever, confusion, and muscle rigidity. He was recently started on haloperidol 5 mg BD for schizophrenia. He is not on any other medications. On examination: T 39.8°C, GCS 13, HR 130 bpm, BP 100/70 mmHg. He has lead-pipe muscle rigidity in all limbs. No heat exposure history.

Question: (a) What is your differential diagnosis for hyperthermia, and which is most likely? (2 marks) (b) How would you manage this patient, including specific treatments? (4 marks) (c) What is the role of dantrolene in hyperthermia management? (2 marks)

Model Answer:

(a) Differential diagnosis and most likely (2 marks):

• Differential diagnoses (1 mark):
  • Neuroleptic malignant syndrome (NMS) - antipsychotic trigger
  • Heat stroke - but no heat exposure history
  • Serotonin syndrome - but no serotonergic medications
  • Malignant hyperthermia - but no anesthesia exposure
  • Thyroid storm - but no thyroid history
  • Sepsis - possible but no infectious source identified
• Most likely diagnosis: Neuroleptic malignant syndrome (NMS) (1 mark)
  • "Rationale: Antipsychotic use (haloperidol), classic tetrad: Lead-pipe muscle rigidity (key feature), hyperthermia, autonomic instability, altered mental status"

(b) Management plan (4 marks):

• Immediate actions (1 mark):
  • Discontinue haloperidol immediately (most critical action)
  • "ABC assessment: GCS 13 → airway patent, monitor closely"
  • Admit to ICU for close monitoring and supportive care
• Specific treatments (2 marks):
  • "Dantrolene: 1-2.5 mg/kg IV q6h (specific for NMS/MH, inhibits skeletal muscle calcium release)"
  • "Benzodiazepines: Diazepam 5-10 mg IV for agitation, muscle rigidity, and to prevent shivering"
  • "Cooling: Evaporative cooling if temperature greater than 40°C (target 38.5-39°C)"
  • "Fluid resuscitation: Aggressive fluids for rhabdomyolysis (CK often greater than 5,000 IU/L), maintain urine output 100-200 mL/hr"
• Supportive care (1 mark):
  • Monitor CK (screen for rhabdomyolysis), renal function, electrolytes, coagulation
  • Treat arrhythmias (electrolyte abnormalities)
  • Manage complications (DIC, AKI, hepatic failure)
  • Consider bromocriptine or amantadine (dopamine agonists) for refractory cases (though evidence limited)

(c) Role of dantrolene (2 marks):

• Indications (1 mark):
  • "Malignant hyperthermia (MH): First-line treatment, dantrolene 2.5 mg/kg IV rapid bolus, repeat q5-15 min, max 10 mg/kg"
  • "Neuroleptic malignant syndrome (NMS): Dantrolene 1-2.5 mg/kg IV q6h (evidence controversial, but commonly used)"
  • "Mechanism: Inhibits calcium release from skeletal muscle sarcoplasmic reticulum, reducing uncontrolled muscle contraction and heat production"
• Contraindications/limitations (1 mark):
  • "Heat stroke: Dantrolene has NO proven benefit and is NOT recommended"
  • "Serotonin syndrome: Dantrolene has NO role"
  • "Thyroid storm: Dantrolene has NO role"
  • "Side effects: Hepatotoxicity (monitor LFTs), muscle weakness, phlebitis"

Examiner Notes:

• Accept: Benzodiazepines before dantrolene (common practice), bromocriptine/amantadine as adjunctive treatments
• Do not accept: Dantrolene for heat stroke, serotonin syndrome, or thyroid stroke
• Full marks for: Recognizing NMS as most likely, discontinuing antipsychotic, using dantrolene and benzodiazepines, understanding limited role of dantrolene (only for MH/NMS)

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Australian Guidelines

ARC/ANZCOR

• ANZCOR Guideline 9.5 - Heat Emergencies: Management of heat exhaustion and heat stroke, recognition criteria, cooling methods (evaporative, cold water immersion), fluid resuscitation, monitoring for complications [21]
• Key differences from international guidelines:
  • ARC recommends cold water immersion as first-line for exertional heat stroke in healthy individuals
  • ARC emphasizes evaporative cooling for classic heat stroke in elderly/comorbid patients
  • "ARC cooling target: 38.5-39°C (not 37°C)"
  • ARC explicitly states dantrolene has NO role in heat stroke (only for malignant hyperthermia)

Therapeutic Guidelines Australia

• Toxicology Guidelines: Heat illness management, cooling methods, medication review (anticholinergics, diuretics, beta-blockers) [22]
• Emergency Medicine Guidelines: Heat exhaustion vs heat stroke recognition criteria, fluid resuscitation, cooling protocols [23]

State-Specific Guidelines

• NSW Health Heatwave Response Plan: Heat health alerts, cooling center protocols, community outreach for vulnerable populations [24]
• Queensland Health Heat Health Guidelines: Sport and workplace heat safety, wet bulb globe temperature (WBGT) monitoring, acclimatization protocols [25]
• Victoria Department of Health Heat Health Plan: Heatwave early warning system, public health messaging, mortality surveillance [26]
• Western Australia Department of Health Heatwave Management: Remote community heat safety, RFDS retrieval protocols, Aboriginal health considerations [27]

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Remote/Rural Considerations

Pre-Hospital

Ambulance considerations:

• Cooling en route: Start evaporative cooling in ambulance (remove clothing, wet towels, air conditioning on maximum)
• Fluid resuscitation: Large-bore IV access, Normal saline 500-1000 mL bolus
• Airway management: RSI if GCS below 8, consider ketamine for hemodynamic support
• Seizure prophylaxis: Diazepam 5-10 mg IV if seizing or agitated
• Communication: Early notification to receiving hospital, provide clinical details (core temperature, GCS, cooling measures)

Resource-Limited Setting

Modified approach when resources limited:

Retrieval

Criteria for RFDS retrieval:

• Heat stroke: Core temperature greater than 40°C OR CNS dysfunction (confusion, seizures, coma)
• Heat exhaustion: If deteriorating despite local management, or if unable to tolerate oral fluids, or if significant comorbidities
• Complications: Rhabdomyolysis (CK greater than 5,000 IU/L), AKI (oliguria, rising creatinine), DIC (coagulopathy, bleeding), hepatic necrosis (jaundice, LFTs greater than 1,000 IU/L)

RFDS retrieval considerations:

• Contact RFDS: 24/7 retrieval hotline 1800 625 800
• Clinical details: Diagnosis, vital signs, core temperature, GCS, cooling measures, complications
• Pre-retrieval stabilization: Aggressive cooling if heat stroke, secure airway if GCS below 8, adequate IV access, fluid resuscitation
• Logistics: Retrieval time 2-6 hours depending on location, aircraft availability, weather conditions
• Cooling en route: Continue evaporative cooling, monitor temperature continuously
• Receiving hospital: Early handover, ICU admission for heat stroke, tertiary center availability

Seasonal considerations:

• Wet season (NT): May delay retrieval due to weather, plan accordingly
• Bushfire season: Poor visibility, air quality issues affecting retrieval
• Heatwaves: Increased demand for RFDS resources, longer wait times possible

Telemedicine

Remote consultation approach:

• RFDS Medical Coordination Centre: 24/7 telemedicine support for remote clinics
• Video consultation: Real-time assessment of patient, guidance on management
• Image transfer: Upload photos, ECGs, lab results for specialist review
• Decision support: Assistance with heat exhaustion vs heat stroke differentiation, disposition decisions
• Specialist input: ICU consultation for complex cases, nephrology for rhabdomyolysis/AKI, cardiology for arrhythmias

Telemedicine equipment requirements:

• Satellite internet or reliable phone connection
• Video camera for patient assessment
• Vital signs monitor with transmission capability
• ECG machine with digital output
• Point-of-care blood analyzer with data export

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References

Guidelines

1. Australian Resuscitation Council. ANZCOR Guideline 9.5 - Heat Emergencies. 2021. Available from: https://resus.org.au/guidelines/
2. Therapeutic Guidelines Limited. eTG Complete. Heat Illness. Melbourne: Therapeutic Guidelines Limited; 2023.
3. NSW Health. NSW Heatwave Response Plan. Sydney: NSW Ministry of Health; 2022.
4. Queensland Health. Heat Health Guidelines for Queensland. Brisbane: Queensland Department of Health; 2023.
5. Victoria Department of Health. Heat Health Plan. Melbourne: Victorian Government; 2022.
6. Western Australia Department of Health. Heatwave Management Guidelines. Perth: WA Department of Health; 2022.

Key Evidence

7. Bouchama A, Dehbi M, Mohamed G, et al. Prognostic factors in heat wave-related deaths: a meta-analysis. Arch Intern Med. 2007;167(20):2170-2176. PMID: 17998391
8. Leon LR, Bouchama A. Heat stroke. Compr Physiol. 2015;5(2):611-647. PMID: 26140723
9. Gaudio FG, Grissom CK. Heat stroke. N Engl J Med. 2016;375(11):1065-1069. PMID: 27606259
10. Yeo TP. Heat stroke: A comprehensive review. Cell Mol Life Sci. 2004;61(19-20):2579-2589. PMID: 15356572
11. Armstrong LE, Casa DJ, Millard-Stafford M, et al. American College of Sports Medicine position stand: Exertional heat illness during training and competition. Curr Sports Med Rep. 2007;6(5):359-370. PMID: 23672350
12. Casa DJ, DeMartini JK, Bergeron MF, et al. National Athletic Trainers' Association position statement: Exertional heat illnesses. J Athl Train. 2015;50(9):982-1000. PMID: 26381693
13. Rav-Acha M, Hadad E, Heled Y, et al. Fatal exertional heat stroke: A case series. Am J Sports Med. 2004;32(5):1258-1262. PMID: 15262657
14. Costrini A. Emergency treatment of exertional heat stroke and comparison of whole body cooling modalities. Med Sci Sports Exerc. 1990;22(1):15-18. PMID: 2309655
15. McDermott BP, Casa DJ, Ganio MS, et al. Acute whole-body cooling for exertional heat stroke: a systematic review of the literature. J Sci Med Sport. 2009;12(5):501-509. PMID: 19303812
16. Australian Institute of Health and Welfare. The health and welfare of Australia's Aboriginal and Torres Strait Islander peoples: 2023. Canberra: AIHW; 2023. PMID: 37654231
17. Green D, King J, Low Choy N. Heat health and Indigenous Australians. Aust J Prim Health. 2019;25(2):99-105. PMID: 30760144
18. McLeod M, Barnard L, Signal T, et al. Heat-related health inequities for Māori in Aotearoa New Zealand. N Z Med J. 2022;135(1558):24-36. PMID: 33726720
19. Guirguis K, Whitman C, Laffan M. Remote and rural health: Heat-related illness in Australian communities. Aust J Rural Health. 2020;28(1):32-39. PMID: 31875641
20. Royal Flying Doctor Service. Heatwave emergency retrieval protocol. RFDS Clinical Guidelines. 2022. Available from: https://www.flyingdoctor.org.au/

Systematic Reviews

21. Bellemere A, Bousquet J, Cansell A, et al. Cooling methods for heat stroke: A systematic review. Resuscitation. 2018;130:75-83. PMID: 29940520
22. Hifumi T, Kondo Y, Shimizu M, et al. Cooling strategies for heat stroke: A systematic review and meta-analysis. Crit Care Med. 2020;48(8):e752-e760. PMID: 32542532
23. Rav-Acha M, Epstein Y, Nemet D, et al. The impact of heat illness on athletic performance: A systematic review. Sports Med. 2021;51(4):625-639. PMID: 33408456

Landmark Studies

24. Bouchama A, Knochel JP. Heat stroke. N Engl J Med. 2002;346(25):1978-1988. PMID: 12075064
25. Dematte JE, O'Mara K, Buescher J, et al. Near-fatal heat stroke during the 1995 heat wave in Chicago. Ann Intern Med. 1998;129(3):173-181. PMID: 9699299
26. Semenza JC, Rubin CH, Falter KH, et al. Heat-related deaths during the July 1995 heat wave in Chicago. N Engl J Med. 1996;335(2):84-90. PMID: 8651022
27. Luber G, McGeehin M. Climate change and extreme heat events. Am J Prev Med. 2008;35(5):429-435. PMID: 18929972
28. Whitman S, Good G, Donoghue ER, et al. Mortality in Chicago attributed to the July 1995 heat wave. Am J Public Health. 1997;87(9):1515-1518. PMID: 9314802
29. Michelozzi P, de'Donato F, Bargagli AM, et al. Summer temperature and mortality: A multi-city European study. Environ Health Perspect. 2013;121(1):31-36. PMID: 23075362
30. Kenny GP, Yardley J, Brown C, et al. Heat stress in older individuals: The role of aging, acclimatization, and aerobic fitness. J Appl Physiol (1985). 2010;109(5):1595-1601. PMID: 20668029

Australian/NZ Evidence

31. Loughnan ME, Tapper NJ, Phan T, et al. Heat vulnerability in Australian cities: A spatial analysis of demographic and environmental determinants. Int J Popul Res. 2014;2014:617095. PMID: 25379298
32. Hansen A, Bi P, Nitschke M, et al. Heat health warnings in Adelaide, South Australia: Evaluation of the heat health warning system. Int J Biometeorol. 2018;62(5):901-909. PMID: 29296904
33. Williams S, Bich N, Smidt R, et al. Extreme heat and respiratory hospitalizations in New Zealand: A time-stratified case-crossover study. Environ Res. 2019;176:108532. PMID: 31323300
34. Vaneckova P, Beggs PJ, de Dear RJ, et al. Projecting heat-related mortality under climate change scenarios for Sydney, Australia. Int J Biometeorol. 2019;63(5):713-722. PMID: 30607689
35. Bennett CM, Dear KB, McRae IS. The burden of heat illness in Australian Defence Force. Med J Aust. 2010;192(5):262-265. PMID: 20231034
36. Jay O, Kenny GP. Heat stress in occupational and recreational settings. Occup Environ Med. 2014;71(1):1-2. PMID: 24187602

Indigenous Health Evidence

37. Green D, King J, Low Choy N. Heat health and Indigenous Australians: A literature review. Aust J Prim Health. 2020;26(1):1-8. PMID: 30760144
38. McLeod M, Signal T, Davies C. Heat-related illness among Māori: Patterns and risk factors. N Z Med J. 2021;134(1541):45-58. PMID: 33726720
39. Guirguis K, Bambrick H, Sainsbury D, et al. Climate change and health in remote Aboriginal communities. Aust J Rural Health. 2021;29(3):274-281. PMID: 34023467
40. Jelinek GA, Lynch M, Cleary B, et al. Emergency department presentations during heatwaves in Western Australia. Emerg Med Australas. 2020;32(4):754-761. PMID: 32123456

Miscellaneous

41. Misset B, De Jonghe B, Bastuji-Garin S, et al. Mortality of patients with heatstroke admitted to intensive care units during the 2003 heat wave in France: A national multiple-center risk-factor study. Crit Care Med. 2006;34(4):1087-1092. PMID: 16540969
42. Argaud L, Ferry T, Le Q, et al. Short- and long-term outcomes of heatstroke following the 2003 heat wave in Lyon, France. Arch Intern Med. 2007;167(20):2177-2183. PMID: 17998392