Intraosseous (IO) Vascular Access

Quick Reference

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ACEM Exam Focus

Primary Written

• Applied anatomy of IO sites (tibial tuberosity, greater tubercle, medial malleolus)
• Axillary nerve proximity to humeral head (10mm distance)
• Pharmacokinetics of IO drug delivery (equivalent to central venous access)
• Complications: extravasation, osteomyelitis, fat embolism, growth plate injury

Primary Viva

• Anatomical basis: Medullary cavity structure, venous drainage of bone marrow, nutrient arteries
• Why IO works: Non-collapsible venous plexus in medullary cavity drains to central circulation
• Humeral vs tibial pharmacokinetics: Humeral closer to heart, faster drug delivery

Fellowship Written (SAQ)

• Indications and contraindications for IO access
• Step-by-step insertion technique for proximal tibia
• Management of failed insertion or extravasation
• Comparison of IO vs IV outcomes in cardiac arrest

Fellowship OSCE

• IO insertion procedural station (manikin or simulation)
• Communication station: Explaining IO to conscious patient
• Resuscitation station: Leading team, establishing IO during arrest

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Key Points

1. IO access is a bridge, not a destination - Replace with IV/CVC within 24 hours. Risk of osteomyelitis increases significantly after 24h. (PMID: 28330919, 31603503, 25661501)

2. Any drug or fluid that can be given IV can be given IO - Includes crystalloids, blood products, vasopressors, antibiotics. Pharmacokinetics equivalent to central venous access. (PMID: 21820577)

3. IV access is superior to IO in cardiac arrest - Recent evidence (2023-2024 meta-analyses) shows IV adrenaline associated with higher ROSC (OR 1.34), better survival, better neurological outcomes compared to IO. Attempt IV first; use IO if IV fails or delayed. (PMID: 36720168, 38219532, 33454244)

4. Humeral IO has twice the flow rate of tibial IO - Proximal humerus: ~213 mL/min; Proximal tibia: ~103 mL/min. Humeral site preferred in cardiac arrest for faster drug delivery. (PMID: 26507111)

5. Conscious patients require lidocaine before infusion - Infusion causes severe intramedullary pressure pain. Give 40mg (2mL) 2% preservative-free lidocaine slowly over 120 seconds, dwell 60 seconds, then flush. (PMID: 21105437, 26437145)

6. First-pass success rates are site and device dependent - Proximal tibia (EZ-IO): 90-99%; Proximal humerus: 70-95%; Sternum (FAST1): 95-98%. Training improves success. (PMID: 21251314, 23047672, 19527063)

7. Watch for extravasation and compartment syndrome - Most common serious complication (0.6%). Monitor limb for swelling, firmness, pain. Stop infusion immediately if suspected; may require fasciotomy. (PMID: 24656089, 15159050, 30889932, 22307197)

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Indications

Absolute Indications

1. Cardiac arrest - Rapid drug delivery required when IV access unsuccessful
2. Shock states - Hypovolaemic, cardiogenic, distributive, obstructive shock with difficult IV access
3. Major trauma - Particularly with burns, crush injuries, amputations preventing peripheral IV
4. Status epilepticus - When IV access impossible due to seizure activity
5. Anaphylaxis - Difficult IV access with life-threatening angioedema
6. Paediatric emergencies - Young children with collapsed peripheral veins

Relative Indications

1. Difficult IV access - Obesity, IV drug use, chronic illness, multiple failed attempts
2. Burns covering potential IV sites - When IV sites compromised by thermal injury
3. Time-critical medication delivery - Antibiotics in septic shock, reversal agents
4. Mass casualty/austere environments - Rapid access for multiple casualties
5. Prehospital setting - EMS/RFDS when IV access challenging in field

When to Consider

IO should be considered early (not as last resort) when:

• Patient requires immediate vascular access AND
• Peripheral IV access is likely to be difficult or time-consuming AND
• Clinical urgency does not permit prolonged attempts

ANZCOR recommendation: Do not delay critical drug administration waiting for IV access. If IV not established quickly, proceed to IO immediately.

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Contraindications

Absolute

Relative

1. Vascular insufficiency in target limb - May worsen ischaemia; consider alternative site
2. Burns/trauma overlying insertion site - Choose alternative site if possible
3. Previous orthopaedic surgery - Altered anatomy, scar tissue may impede insertion
4. Coagulopathy - Increased bleeding risk but NOT absolute contraindication in life-threatening emergency
5. Obesity - Landmarks difficult to palpate; may require ultrasound guidance or 45mm needle

Risk-Benefit Considerations

In life-threatening emergencies (cardiac arrest, haemorrhagic shock, status epilepticus):

• Relative contraindications may be acceptable
• Benefits of vascular access outweigh risks
• Document decision-making
• Choose alternative site if available
• Monitor for complications

Example: Patient in cardiac arrest with bilateral lower limb fractures → Use proximal humeral IO instead of tibial sites.

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Anatomy

Surface Landmarks

Proximal Tibia (Most Common Site)

Patient positioning: Knee flexed 30 degrees, sandbag/towel under knee

Direction of insertion: Perpendicular to bone (90 degrees) or slightly caudal (avoid growth plate in children)

Proximal Humerus (Preferred in Cardiac Arrest)

Patient positioning: Arm adducted, hand on abdomen (internal rotation brings greater tubercle lateral)

Direction of insertion: 45 degrees toward opposite hip

Distal Tibia (Alternative Site)

Patient positioning: Foot in neutral position

Direction of insertion: Perpendicular to bone, slightly cephalad

Sternum (Specialized Device - FAST1)

Success rate: 95-98% (PMID: 19169166)

Contraindication: Chest trauma, CPR in progress, sternotomy scar

Deep Anatomy

Medullary Cavity Structure

Skin → Subcutaneous tissue → Periosteum → Cortical bone → Medullary cavity
                                                                    ↓
                                                        Trabecular bone + bone marrow
                                                                    ↓
                                                        Venous sinusoids (non-collapsible)
                                                                    ↓
                                                        Nutrient veins → Systemic circulation

Why IO works:

• Medullary cavity contains rich venous plexus supported by trabecular bone
• Venous sinusoids do NOT collapse in shock (unlike peripheral veins)
• Nutrient veins drain directly to central circulation via emissary veins
• Drug/fluid enters bone marrow → venous plexus → central circulation (equivalent to central venous access) (PMID: 17169880, 20042440)

Blood Flow Pathway

Proximal tibia: Medullary cavity → Nutrient veins → Popliteal vein → Femoral vein → IVC → Right atrium

Proximal humerus: Medullary cavity → Nutrient veins → Axillary vein → Subclavian vein → SVC → Right atrium (shorter pathway, faster delivery)

Danger Zones

Safe insertion technique:

• Proximal humerus: Identify greater tubercle, insert at 45-degree angle; do NOT advance beyond cortex
• Proximal tibia: Stay 2cm distal and 2cm medial to tuberosity; do NOT aim laterally
• Advance needle ONLY until loss of resistance felt - Stop immediately when entering medullary cavity

Anatomical Variants

1. Obesity (BMI greater than 30): Landmarks obscured by adipose tissue; skin-to-bone distance may exceed 25mm (standard needle insufficient). Use 45mm (yellow) needle or ultrasound guidance. (PMID: 21616462, 26038497, 21109104, 30121111)

2. Paediatric anatomy:

   • Growth plates closer to insertion points
   • Thinner cortex (easier insertion but higher fracture risk)
   • Smaller medullary cavity

3. Elderly: Osteoporosis may cause needle to "plunge" through posterior cortex; use gentle controlled pressure

4. Previous orthopaedic surgery: Altered anatomy, intramedullary rods may obstruct placement

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Equipment

Essential Equipment

Optional Equipment

Equipment Sizing

Adult

Rule of thumb: If 5mm black mark on needle not visible when tip touches bone, needle is too short. Use longer needle.

Paediatric

Growth plate warning: In paediatric patients, insert at least 1-2cm away from growth plate to avoid physeal injury

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Devices

EZ-IO (Vidacare/Teleflex) - Battery-Powered Drill

Advantages:

• Highest first-pass success rate (90-99%) (PMID: 21251314, 23545593)
• Rapid insertion (seconds)
• Minimal force required
• Disposable needles with stylet

Disadvantages:

• Requires battery maintenance
• Cost (device + disposable needles)
• Noise may alarm patients/family

Technique:

1. Select needle (15/25/45mm)
2. Attach needle to driver
3. Position perpendicular to bone
4. Apply gentle pressure while squeezing trigger
5. Stop when loss of resistance felt (needle enters medullary cavity)
6. Remove driver; stabilizer flange remains

Success rate: Proximal tibia 97.3%, Proximal humerus 88% (PMID: 21251314, 19527063)

BIG (Bone Injection Gun) - Spring-Loaded

Advantages:

• No battery required
• Lightweight
• Single-use

Disadvantages:

• Lower success rate than EZ-IO (75-85%) (PMID: 21342672)
• Higher rate of "short shoots" (needle not reaching marrow)
• More difficult in obese patients
• Can be painful for operator (recoil)

Technique:

1. Remove safety cap
2. Position device perpendicular to bone
3. Apply firm downward pressure
4. Press trigger button; spring drives needle into bone
5. Remove trigger mechanism; needle and stabilizer remain

NIO (New Intraosseous) - Manual/Spring-Loaded Hybrid

Advantages:

• Newer design with improved success (91%) (PMID: 27431440)
• No battery required

Disadvantages:

• Less widely available than EZ-IO or BIG

FAST1 (First Access for Shock and Trauma) - Sternal Device

Indication: Sternal IO insertion (specialized device required)

Advantages:

• High success rate (95-98%) (PMID: 19169166)
• Sternum accessible in trauma when limbs unavailable
• Used in military settings

Disadvantages:

• Single-use, expensive
• Contraindicated in chest trauma, CPR, sternotomy scar
• Removal more complex

Manual Needle (Jamshidi or Cook IO Needle)

Indication: Low-resource settings, austere environments

Technique: Insert with drilling/twisting motion; requires significant force and operator skill

Disadvantages: Low success rate without training, higher complication rate

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Preparation

Patient Preparation

1. Consent/Explanation (if conscious):

   • "We need to give you fluids/medication urgently"
   • "Your veins are difficult to access, so we'll insert a special needle into your bone to deliver treatment"
   • "You'll feel pressure and a brief sharp pain, then we'll give you local anaesthetic to numb the area"
   • Pause for questions if time permits

2. Positioning:

   • Proximal tibia: Supine, knee flexed 30 degrees over sandbag/towel
   • Proximal humerus: Supine or sitting, arm adducted across chest/abdomen
   • Distal tibia: Supine, foot in neutral position

3. Monitoring:

   • Ensure continuous cardiac monitoring, pulse oximetry
   • Blood pressure cuff on opposite limb

4. Pre-procedure analgesia (if conscious):

   • Consider intranasal fentanyl, small IV dose opioid if access available
   • Warn patient about pressure sensation

Operator Preparation

1. Standard precautions (PPE):

   • Cardiac arrest/true emergency: Non-sterile gloves acceptable
   • Semi-urgent: Sterile gloves, eye protection

2. Hand hygiene: Alcohol-based hand rub or soap and water

3. Equipment check:

   • Confirm IO device functional (battery charged if EZ-IO)
   • Confirm needle size appropriate for patient/site
   • Ensure flush syringes prepared
   • Lidocaine drawn up (2mL) if patient conscious

4. Assistance arranged: Second person to assist with stabilizing limb, handing equipment

5. Backup plan identified: If first site fails, identify second site (e.g., if right proximal tibia fails → attempt left proximal tibia or proximal humerus)

Site Preparation

1. Sterile technique:

   • Cardiac arrest/true emergency: Clean technique acceptable (wipe site with chlorhexidine/alcohol)
   • Semi-urgent/elective: Full aseptic technique with sterile gloves, wide prep

2. Skin preparation:

   • Chlorhexidine 2% in 70% alcohol (allow to dry 30 seconds)
   • Povidone-iodine if chlorhexidine allergy

3. Draping:

   • Not required in cardiac arrest
   • Fenestrated drape if time permits

4. Local anaesthesia (conscious patient):

   • Infiltrate skin and periosteum with 1% lidocaine + adrenaline (2-5mL)
   • Wait 1-2 minutes for effect
   • Note: This does NOT anaesthetize intramedullary space (lidocaine flush required after insertion)

Positioning

• Patient position: As per site (see "Patient Preparation" above)
• Operator position: Stand on same side as insertion site, facing patient
• Assistant position: Opposite side, ready to stabilize limb and receive device/equipment

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Procedure Steps

Step 1: Landmark Identification

Proximal tibia:

• Palpate tibial tuberosity (most prominent point below patella)
• Measure 2cm distal (toward foot), 2cm medial (toward midline)
• Mark insertion point with skin marker or thumbnail indentation
• Common error: Inserting too lateral (risk of anterior tibial artery) or too proximal (risk of growth plate in children)

Proximal humerus:

• Position arm across chest/abdomen (internal rotation)
• Palpate greater tubercle (most lateral bony prominence of shoulder)
• Insertion point at peak of greater tubercle
• Common error: Inserting too distal (surgical neck → axillary nerve injury)

Distal tibia:

• Palpate medial malleolus
• Insertion point 2-3cm proximal to tip of malleolus, on flat anteromedial surface
• Common error: Inserting through malleolus itself (too much cortical bone)

Step 2: Skin Preparation and Draping

• Clean site with chlorhexidine 2%/alcohol in circular motion, outward from insertion point
• Allow antiseptic to dry 30 seconds
• Apply fenestrated drape if time permits (NOT in cardiac arrest)

Step 3: Local Anaesthesia (Conscious Patient)

• Infiltrate skin and periosteum with 2-5mL 1% lidocaine with adrenaline
• Warn patient: "Sharp scratch"
• Wait 1-2 minutes
• Test sensation before proceeding

Step 4: Needle Insertion

EZ-IO technique:

1. Attach needle to driver (twist clockwise until "click")
2. Position driver perpendicular to bone (90 degrees)
   • Exception: Proximal humerus 45 degrees toward opposite hip
3. Apply gentle downward pressure
4. Squeeze trigger; driver rotates needle through cortex
5. Stop when loss of resistance felt (needle enters medullary cavity)
   • Tactile feedback: "pop" or sudden give
   • Typical depth: 1-2cm
6. Release trigger
7. Unscrew and remove driver (twist counter-clockwise)
8. Stabilizer flange remains on skin

BIG technique:

1. Position BIG perpendicular to bone
2. Apply firm downward pressure
3. Press trigger; spring drives needle into bone
4. Remove trigger assembly
5. Stabilizer remains

Key point: Do NOT advance needle beyond loss of resistance. Advancing too far perforates posterior cortex → extravasation.

Common error: Insufficient pressure before triggering (needle fails to reach bone) OR excessive advancement (perforate posterior cortex)

Step 5: Remove Stylet

• Twist stylet counter-clockwise and remove
• Needle lumen now open to medullary cavity

Step 6: Confirm Placement

Four confirmation methods (all should be present):

If unable to confirm placement:

• Attempt aspiration with larger syringe (20mL)
• Flush 5-10mL saline; watch for:
  • Fluid flows easily → Correct placement
  • Resistance or swelling → Extravasation; remove needle, attempt different site

Step 7: Administer Lidocaine (Conscious Patient)

Lidocaine protocol (PMID: 21105437, 26437145):

1. Draw up 40mg (2mL) 2% preservative-free lidocaine
2. Warn patient: "You'll feel pressure in your leg/arm for about 30-60 seconds"
3. Administer slowly over 120 seconds (slow push minimizes pressure pain)
4. Allow 60-second dwell time (lidocaine anaesthetizes intramedullary nerves)
5. Flush with 5-10mL normal saline

Paediatric dose: 0.5mg/kg (maximum 40mg)

If pain recurs during infusion: Repeat with 20mg (1mL) lidocaine

Step 8: Connect IV Extension and Secure

1. Attach primed IV extension tubing to IO needle hub
2. Secure needle with adhesive dressing:
   • Apply gauze pad around needle hub
   • Secure with transparent dressing OR adhesive tape
   • Avoid circumferential wrapping (impedes limb assessment)
3. Label insertion site with date and time

Common error: Wrapping limb circumferentially prevents detection of compartment syndrome

Step 9: Commence Infusion

1. Attach IV fluid bag to extension tubing
2. Gravity flow is INSUFFICIENT for rapid infusion - Use:
   • Pressure infuser bag (inflate to 300mmHg) OR
   • Manual pressure (squeeze bag) OR
   • Syringe push (10-20mL boluses)
3. Follow all medications with 10-20mL saline flush (ensure drug reaches systemic circulation)

Flow rates:

• Proximal humerus: 213 mL/min (under pressure) (PMID: 26507111)
• Proximal tibia: 103 mL/min (under pressure)
• Gravity flow: 20-30 mL/min (insufficient for resuscitation)

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Ultrasound Guidance

When to Use

1. Obesity - Landmarks not palpable, skin-to-bone distance unknown
2. Difficult anatomy - Previous surgery, trauma, oedema obscuring landmarks
3. Failed blind attempt - Confirm correct landmark before second attempt
4. Training/education - Visualize needle trajectory, confirm placement

Evidence: Ultrasound superior to palpation for landmark identification in obese patients (PMID: 28416035, 31080034, 27013149)

Probe Selection

Technique

Landmark identification:

1. Place probe in transverse orientation over suspected insertion site
2. Identify hyperechoic (bright) cortex with posterior acoustic shadowing
3. Measure skin-to-bone distance; select needle accordingly:
   • below 25mm → 25mm needle
   • 25-40mm → 45mm needle
   • greater than 40mm → Consider alternative site or surgical cutdown

Real-time guidance (advanced):

1. Use in-plane approach (needle parallel to probe)
2. Visualize needle tip advancing through soft tissue
3. Confirm contact with cortex
4. Loss of visualization as needle enters marrow (acoustic shadowing)

Confirmation:

1. Look for echogenic "flash" in medullary cavity during saline flush
2. Absence of expanding hypoechoic area around bone (rules out extravasation)

Sonographic Anatomy

Proximal tibia:

• Hyperechoic tibial tuberosity with posterior shadowing
• Insertion point 2cm distal and medial; cortex appears flat and smooth

Proximal humerus:

• Hyperechoic rounded contour of humeral head
• Greater tubercle is most lateral prominence

Distal tibia:

• Hyperechoic medial malleolus; insertion point proximal to malleolus on flat shaft

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Paediatric Considerations

Age-Specific Modifications

Paediatric-Specific Considerations

1. ANZCOR Guideline 12.2: If IV access not achieved in 1 minute or after 2-3 attempts, insert IO immediately (PMID: 33085812)

2. Growth plate injury risk:

   • Proximal tibia physis located ~1cm below tibial tuberosity
   • Insert at least 1-2cm distal to tuberosity
   • Avoid excessive force or needle angulation
   • Long-term sequelae rare but reported (PMID: theoretical risk)

3. Needle sizing:

   • Neonates/infants: 15mm (pink)
   • Do NOT use adult 25mm needle in neonates (risk of posterior cortex perforation)

4. Conscious paediatric patients:

   • Pre-procedure anxiolysis (intranasal fentanyl, midazolam if time permits)
   • Lidocaine dose: 0.5mg/kg (max 40mg)
   • Parental presence vs. absence: Discuss with team

5. Fluid resuscitation:

   • Bolus: 10-20mL/kg normal saline or blood
   • Requires pressure bag or manual push (gravity insufficient)

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Complications

Immediate Complications

Delayed Complications

Complication Prevention

To minimize extravasation/compartment syndrome:

1. Confirm loss of resistance before removing stylet
2. Perform flush test BEFORE rapid infusion
3. Monitor limb frequently during infusion (every 5-10 minutes)
4. Avoid circumferential dressings/wrapping
5. STOP infusion immediately if resistance, swelling, or pain

To minimize osteomyelitis:

1. Use aseptic technique (chlorhexidine skin prep, sterile gloves when possible)
2. Remove IO needle within 24 hours (replace with IV/CVC as soon as feasible)
3. Avoid IO in bacteraemic patients if alternative available

To minimize failed insertion:

1. Identify landmarks carefully; use ultrasound if uncertain
2. Select appropriate needle length (check 5mm mark visible when tip touches bone)
3. Ensure perpendicular orientation (except humeral 45 degrees)
4. Advance with controlled pressure; STOP at loss of resistance

To minimize pain (conscious patients):

1. Infiltrate skin/periosteum with local anaesthetic before insertion
2. Always give intramedullary lidocaine 40mg before flushing/infusing
3. Slow push over 120 seconds; allow 60-second dwell time
4. Warn patient about pressure sensation

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Troubleshooting

Rescue Techniques

If first IO attempt fails:

1. Do NOT reattempt same bone within 48 hours (risk of extravasation through cortical defect)
2. Choose alternative site:
   • Failed right proximal tibia → Left proximal tibia OR proximal humerus
   • Failed proximal humerus → Proximal tibia OR distal tibia
3. Consider alternative access:
   • Ultrasound-guided peripheral IV (basilic, brachial, femoral vein)
   • External jugular vein (if trained)
   • Central venous catheter (if time permits and skilled operator available)
   • Venous cutdown (rarely required; resource-intensive)

If multiple IO attempts fail:

• Senior clinician review
• Consider anatomical variants, obesity (ultrasound guidance)
• Escalate to central venous access or surgical cutdown

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Drug Administration

Medications and Fluids

Administration Technique

1. ALWAYS follow medication with 10-20mL normal saline flush - Ensures drug reaches systemic circulation (medication remains in medullary cavity unless flushed)

2. Use pressure for rapid administration:

   • Pressure infuser bag (300mmHg) for rapid fluid resuscitation
   • Manual syringe push (10-20mL boluses) for medications
   • Gravity flow insufficient for rapid infusion (20-30 mL/min)

3. Drug onset times equivalent to IV/central access:

   • Proximal humerus: Faster than tibial (closer to heart)
   • Proximal tibia: Onset within 30-60 seconds (equivalent to peripheral IV)

Blood Sampling

IO blood samples can be used for laboratory analysis:

Acceptable for:

• Full blood count, haemoglobin
• Electrolytes (Na, K, Cl, HCO3)
• Urea, creatinine
• Glucose
• Lactate
• Blood cultures (if no other access available)
• Blood gas analysis (correlates with venous gas) (PMID: 1554183)

Unreliable for:

• Coagulation studies (INR, APTT) - May be affected by bone marrow contents
• Calcium, phosphate - Altered by bone marrow

Technique:

1. Aspirate 2-5mL bone marrow with 10mL syringe (discard)
2. Aspirate blood for samples with fresh syringe
3. Transfer to appropriate sample tubes

Note: Discuss with laboratory if sending IO samples; some labs may not accept IO blood for certain assays.

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IO vs IV in Cardiac Arrest

Why IV Superior to IO?

Hypotheses:

1. Pharmacokinetics: IO drugs (especially tibial) have slower peak plasma concentration and lower "first-pass" myocardial delivery compared to peripheral IV (PMID: 21756969)
2. Site matters: Humeral IO may be closer to IV outcomes than tibial IO, but most clinical data involves tibial placement
3. Circulation during CPR: Peripheral veins receive better flow during chest compressions than bone marrow venous plexus (PMID: 32084521)

Current Guidelines (ANZCOR Guideline 3.3)

Vascular access in adult cardiac arrest:

1. First-line: Peripheral IV (antecubital fossa preferred) - 2 attempts or 60-90 seconds
2. Second-line: IO (proximal humerus preferred for faster drug delivery)
3. Consider: Central venous access if skilled operator and IV/IO failed

If using IO in cardiac arrest:

• Proximal humerus preferred over proximal tibia (closer to heart, flow rate 213 mL/min vs 103 mL/min) (PMID: 26507111)
• Use pressure infuser or manual flush for all drugs (gravity insufficient)
• ALWAYS flush with 20mL saline after each drug

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Post-Procedure Care

Immediate Care

1. Confirm placement:

   • Needle stable
   • Aspiration of bone marrow (may fail in arrest)
   • 10mL saline flush without resistance or extravasation

2. Secure needle:

   • Adhesive dressing over stabilizer
   • Avoid circumferential wrapping
   • Label site with date and time

3. Commence infusion/medication:

   • Lidocaine first if conscious patient
   • Use pressure for rapid infusion
   • Flush after all medications

4. Documentation:

   • Time of insertion
   • Site used
   • Needle size
   • Indications
   • Number of attempts
   • Confirmation of placement
   • Complications
   • Medications/fluids administered

Monitoring

Signs of complication requiring immediate action:

• Swelling around site → Extravasation
• Increasing limb girth → Compartment syndrome
• Severe pain, paraesthesia, pulselessness → Neurovascular compromise
• Resistance to infusion → Needle occlusion or displacement
• Fever, erythema, purulent discharge → Infection

Replacement with IV/CVC

IO is a bridge, not a destination:

1. As soon as patient stabilized, attempt peripheral IV or central venous access
2. Remove IO within 24 hours - Risk of osteomyelitis increases significantly after 24h (PMID: 31603503, 25661501)
3. Document reason if IO in situ greater than 24 hours (e.g., multiple failed IV attempts, awaiting interventional radiology CVC, surgeon review)

IO Needle Removal

Technique (PMID: 31603503):

1. Discontinue all infusions
2. Disconnect extension tubing
3. Stabilize limb
4. Remove dressing
5. Twist needle clockwise while pulling straight out (use EZ-IO driver or manual twist)
   • Do NOT rock needle - This enlarges cortical defect and increases extravasation risk
6. Apply firm pressure to site for 5 minutes
7. Apply sterile occlusive dressing

Post-removal care:

• Monitor site for 24-48 hours
• Watch for hematoma, swelling, erythema, purulent discharge
• Patient education: "If you develop increasing pain, redness, swelling, fever, return to ED"

Imaging Confirmation

Rarely required - Clinical confirmation (aspiration, flush test) sufficient

Consider imaging if:

• Uncertain needle position
• Suspicion of extravasation or fracture
• Complications during insertion

Imaging modality:

• X-ray: Confirms needle in medullary cavity; can identify fracture, extraosseous placement
• Ultrasound: Can visualize needle tip, check for fluid collection around bone

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Australian/NZ Context

ANZCOR Guidelines

ANZCOR Guideline 3.3 - Advanced Life Support (Adults):

• IV access preferred first-line for drug delivery in cardiac arrest
• If IV access not established within 60-90 seconds or 2 attempts, proceed to IO immediately
• IO efficacy equivalent to IV for drug delivery, but recent evidence suggests IV associated with better outcomes
• Proximal humerus or proximal tibia recommended sites
• Citation: PMID: 33083312 (2020 ILCOR CoSTR Adult Life Support)

ANZCOR Guideline 12.2 - Advanced Life Support for Infants and Children:

• If IV access not established within 1 minute or after 2-3 attempts, insert IO
• IO route as effective as IV for all resuscitation drugs and fluids
• Proximal tibia preferred site in children
• Citation: PMID: 33085812 (2020 ILCOR Paediatric Life Support CoSTR)

Credentialing

ACEM Credential Level: Core Procedure

All ACEM trainees must demonstrate competency in IO access:

• Logbook requirements: Minimum 5 supervised insertions (or simulation-based assessment)
• Sites: Proximal tibia (mandatory), proximal humerus (desirable)
• Devices: Training on EZ-IO (most common in Australian EDs)

Supervision requirements:

• Advanced trainees: Supervised for first 5 insertions, then independent
• SHOs/RMOs: Must be supervised until deemed competent by senior clinician

Australian/NZ Clinical Considerations

1. Device availability:

   • EZ-IO most common in Australian/NZ EDs, EMS services
   • Some services use BIG or manual needles
   • Sternal devices (FAST1) rare in civilian practice (military/retrieval medicine)

2. PBS considerations:

   • IO access devices NOT on PBS (hospital/EMS budget)
   • Lidocaine (preservative-free) available on PBS

3. State-specific protocols:

   • Most states follow ANZCOR guidelines
   • Local variations in paramedic scope of practice (some states allow IO by paramedics, others ALS only)

Indigenous Health Considerations

Aboriginal and Torres Strait Islander Health

Epidemiology:

• Higher rates of critical illness requiring emergency vascular access (sepsis, trauma, cardiovascular disease)
• Higher rates of diabetes → peripheral vascular disease, difficult IV access (PMID: 30760144)
• Higher rates of chronic kidney disease → vascular access challenges from fistulae, previous catheters (PMID: 26040576)

Communication and Cultural Safety:

1. Explain procedure clearly: Use plain language; avoid medical jargon
2. Family involvement: Encourage family presence if patient desires (culturally important)
3. Respect for body: Some Aboriginal cultures have specific beliefs about body integrity; explain necessity and temporary nature of IO
4. Use Aboriginal Health Workers/Liaison Officers when available for communication and cultural support

Practical considerations:

• Obesity rates higher in some Aboriginal communities → May require 45mm needle, ultrasound guidance
• Remote communities: IO may be only vascular access option until RFDS retrieval

Māori Health (New Zealand)

Epidemiology:

• Higher rates of cardiovascular disease, diabetes → Vascular access challenges
• Higher rates of obesity → Difficult landmarks, require longer needles

Cultural Considerations:

1. Whānau (family) involvement: Include whānau in decision-making where appropriate
2. Tikanga (cultural protocols): Respect for the body; explain procedure and temporary nature
3. Manaakitanga (caring, respect): Demonstrate respect and care during procedure
4. Use Māori Health Services when available for cultural support

Remote/Rural/RFDS Considerations

Challenges in Remote Settings:

1. Limited resources: May only have manual IO needles (no EZ-IO battery)
2. Limited backup: If IO fails, no immediate surgical backup for cutdown or CVC
3. Prolonged transport times: IO may need to remain in situ during RFDS retrieval (aim to remove within 24h; document if exceeds)
4. Environmental factors: Dust, heat, limited sterile supplies

RFDS Retrieval Medicine:

1. IO preferred for critically unwell patients during retrieval - More secure than peripheral IV during transport, turbulence (PMID: 18666230)
2. Humeral site preferred if possible (higher flow rate, easier to monitor during flight)
3. Secure needle well - Vibration during flight/road retrieval can dislodge needle
4. Monitor limb frequently - Difficult to detect extravasation/compartment syndrome during noisy transport

Pre-Hospital (EMS/Paramedic) Use:

• IO standard of care in Australian/NZ EMS for cardiac arrest, trauma, difficult IV access (PMID: 21856044)
• Proximal tibia most common site (easier in field, patient positioning)
• Handover to ED: Document IO insertion time, site, drugs/fluids given, complications

Remote Area Nursing:

• IO training essential for remote area nurses
• May be sole vascular access option until RFDS arrival
• Telemedicine support available (RFDS on-call doctor can guide via phone/video)

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OSCE Practice

OSCE Station 1: IO Insertion (Procedural Station)

Format: Procedural skills assessment
Time: 11 minutes
Equipment: Manikin with IO insertion capability, EZ-IO device with 25mm needle, chlorhexidine swabs, sterile gloves, 10mL syringes (×2), normal saline, IV extension tubing, adhesive dressing

Candidate Instructions:

You are the Emergency Registrar. A 45-year-old male has been brought to the Emergency Department in cardiac arrest. CPR is in progress. The nurse has attempted peripheral IV access twice without success. Your consultant asks you to establish intraosseous (IO) access in the proximal tibia.

Task: Insert an IO needle in the proximal tibia of the manikin and confirm placement. Verbalise your steps as you proceed.

Examiner Instructions:

• Manikin positioned supine
• EZ-IO device with charged battery, 25mm needle available
• Observe sterile technique, landmark identification, insertion technique, confirmation

Marking Criteria:

Pass mark: 10/14

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OSCE Station 2: Communication - IO in Conscious Patient

Format: Communication station
Time: 11 minutes
Equipment: None (role-play)

Candidate Instructions:

You are the Emergency Registrar. A 60-year-old female has presented with septic shock (BP 75/40, HR 130, lactate 8.5). She is conscious and alert. Your team has attempted peripheral IV access three times without success. You have decided to insert intraosseous (IO) access in the proximal tibia.

Task: Explain the procedure to the patient and obtain verbal consent.

Actor Briefing:

• You are a 60-year-old woman feeling very unwell and frightened
• You are alert but anxious
• You have never heard of IO access
• You are worried about pain
• You will consent if the doctor explains clearly and reassures you

Marking Criteria:

Pass mark: 9/13

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OSCE Station 3: Resuscitation - Cardiac Arrest with IO Access

Format: Resuscitation station
Time: 11 minutes
Equipment: Manikin with defibrillator, IO already in situ (proximal tibia), IV medications (adrenaline, amiodarone), syringes, saline flushes

Candidate Instructions:

You are the Emergency Registrar leading a cardiac arrest. A 55-year-old male collapsed with witnessed VF arrest. CPR is in progress. The nurse has inserted IO access (proximal tibia). You have just delivered the first shock.

Task: Lead the team through the next 2 minutes of the cardiac arrest. The defibrillator will prompt you when ready.

Examiner Instructions:

• Manikin in VF throughout (no ROSC)
• Nurse and doctor available to assist
• Defibrillator prompts at 2-minute intervals
• Assess team leadership, drug administration via IO, systematic approach

Marking Criteria:

Pass mark: 9/13

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Viva Questions

Viva Question 1: Indications and Contraindications

Stem: "A 4-year-old child presents to your Emergency Department in status epilepticus. After 10 minutes of seizure activity, your team has failed to establish IV access."

Q1: What are the indications for intraosseous access?

Model Answer: IO access is indicated when urgent/emergency vascular access is required AND peripheral IV access has failed or is not achievable quickly.

Specific indications include:

1. Cardiac arrest - Adult: Failed IV within 60-90 seconds; Paediatric: Failed IV within 1 minute (ANZCOR Guidelines 3.3, 12.2)
2. Shock states - Hypovolaemic, septic, cardiogenic, obstructive shock with difficult IV access
3. Status epilepticus - As in this scenario; IV impossible due to ongoing seizure
4. Trauma - Burns, amputations, crush injuries preventing peripheral IV
5. Paediatric emergencies - Young children with collapsed peripheral veins
6. Difficult IV access - Obesity, IV drug use, chronic illness, multiple failed attempts

In this scenario: 4-year-old in status epilepticus with failed IV access = absolute indication for IO. ANZCOR Guideline 12.2 states if IV not achieved in 1 minute, proceed to IO immediately.

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Q2: What are the absolute contraindications to IO access?

Model Answer:

Absolute contraindications (must NOT insert IO):

1. Fracture in target bone - Risk of extravasation through fracture line
2. Recent IO attempt in same bone (within 24-48h) - Risk of extravasation through cortical defect
3. Infection/cellulitis at insertion site - Risk of introducing infection into bone marrow → osteomyelitis
4. Prosthetic joint or hardware in target bone - Risk of seeding infection, damage to hardware
5. Osteogenesis imperfecta or severe osteoporosis - Risk of fracture during insertion

Relative contraindications (consider alternative site):

• Vascular insufficiency in limb
• Burns/trauma overlying site
• Previous orthopaedic surgery
• Coagulopathy (NOT absolute contraindication in life-threatening emergency)

In this scenario: If child has fractured right tibia → DO NOT insert IO in right tibia; use left tibia or proximal humerus instead.

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Q3: Where would you insert the IO in this 4-year-old child, and what size needle would you use?

Model Answer:

Site: Proximal tibia (preferred in paediatric patients - ANZCOR Guideline 12.2)

Landmark identification:

• Palpate tibial tuberosity (most prominent point below patella)
• Insertion point: 2cm distal (toward foot), 2cm medial (toward midline) from tibial tuberosity
• Flat anteromedial surface of tibia

Positioning: Knee flexed 30 degrees over sandbag/towel

Needle size: 15mm (pink) or 25mm (blue) depending on child's size

• 4-year-old typically 15-20kg → 15-25mm needle
• Use EZ-IO sizing: If 5mm black mark not visible when needle tip on bone, need longer needle

Alternative site if proximal tibia contraindicated: Distal tibia (2-3cm proximal to medial malleolus)

Growth plate consideration: Proximal tibial physis located ~1cm below tibial tuberosity; insertion point 2cm distal minimizes risk of physeal injury

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Viva Question 2: Anatomy and Pharmacology

Stem: "You are inserting an IO needle in the proximal humerus of an adult patient in cardiac arrest."

Q1: Describe the relevant anatomy for proximal humeral IO insertion.

Model Answer:

Surface anatomy:

• Greater tubercle - Most lateral bony prominence of humeral head; insertion point
• Acromion - Greater tubercle located 1-2cm distal to acromion
• Surgical neck - DANGER ZONE; 1cm distal to insertion point; axillary nerve wraps around surgical neck

Positioning: Arm adducted across chest/abdomen (internal rotation) - Brings greater tubercle into lateral position for palpation

Insertion technique:

• Insertion point: Peak of greater tubercle
• Angle: 45 degrees toward opposite hip
• Direction: Into humeral head (epiphysis/metaphysis)

Deep anatomy:

• Skin → Deltoid muscle → Periosteum → Cortical bone → Medullary cavity of humeral head
• Medullary cavity contains trabecular bone + bone marrow + venous sinusoids

Structures at risk:

How to avoid injury:

• Identify greater tubercle accurately (NOT surgical neck)
• Insert at 45-degree angle toward opposite hip
• STOP at loss of resistance (do NOT advance beyond medullary cavity)

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Q2: Why does the proximal humerus have faster drug delivery than the proximal tibia in cardiac arrest?

Model Answer:

Pharmacokinetic advantage of humeral IO:

1. Shorter pathway to heart:

   • Humeral: Medullary cavity → Nutrient veins → Axillary vein → Subclavian vein → SVC → Right atrium
   • Tibial: Medullary cavity → Nutrient veins → Popliteal vein → Femoral vein → IVC → Right atrium
   • Humeral route is anatomically closer to central circulation

2. Higher flow rates (PMID: 26507111):

   • Humeral: ~213 mL/min (under pressure)
   • Tibial: ~103 mL/min (under pressure)
   • Humeral IO delivers fluids/drugs twice as fast as tibial

3. Faster peak plasma concentration:

   • Drugs given via humeral IO reach therapeutic levels faster
   • Particularly important for time-critical drugs (adrenaline, amiodarone in cardiac arrest)

Clinical implication:

• ANZCOR Guideline 3.3 recommends proximal humerus OR proximal tibia for cardiac arrest
• Proximal humerus preferred if trained due to faster delivery
• However, IV access superior to IO (recent evidence shows IV associated with better ROSC, survival, neurological outcomes) - PMID: 36720168, 38219532

Caveats:

• Humeral insertion more technically challenging (lower first-pass success rate 70-95% vs tibial 90-99%)
• Requires training and practice

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Q3: Can you give blood products via IO access?

Model Answer:

Yes - all blood products can be given via IO route:

• Packed red blood cells (PRBC)
• Fresh frozen plasma (FFP)
• Platelets
• Cryoprecipitate
• Whole blood

Pharmacokinetics: Equivalent to IV administration

Practical considerations:

1. Viscosity: Blood products are viscous; require pressure infusion

   • Use pressure bag (inflate to 300mmHg) OR
   • Manual syringe push (10-20mL boluses)
   • Gravity flow insufficient (20-30 mL/min)

2. Flow rates:

   • Humeral IO: 213 mL/min (under pressure) - Can deliver 1 unit PRBC in ~2-3 minutes
   • Tibial IO: 103 mL/min - Slower but acceptable

3. Flush: Follow blood product with 10-20mL saline flush

4. Filters: Standard blood administration sets with filters can be used (IO route does NOT require special filters)

Haemolysis: No significant haemolysis with IO administration of blood products (equivalent to IV) (PMID: 20157468)

Clinical scenario: Massive transfusion protocol in trauma patient with failed IV access - IO is acceptable route for blood product administration until IV/CVC established. (PMID: 10866253)

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Viva Question 3: Complications and Management

Stem: "You have inserted an IO needle in the proximal tibia of a 60-year-old male in septic shock. Five minutes after commencing rapid fluid resuscitation, the nurse alerts you to swelling around the IO site."

Q1: What is your immediate management?

Model Answer:

Immediate recognition: Swelling around IO site = Extravasation

Immediate actions:

1. STOP infusion immediately - Prevent further fluid entering soft tissue
2. Remove IO needle - Twist clockwise while pulling straight out
3. Elevate limb - Reduce oedema
4. Assess neurovascular status - Check for compartment syndrome:
   • 5 Ps: Pain (out of proportion), Pallor, Paraesthesia, Pulselessness, Paralysis
   • Palpate compartments (firmness, tenderness)
   • Passive stretch test (pain with passive dorsiflexion = anterior compartment syndrome)
5. Establish alternative vascular access:
   • Attempt peripheral IV (other limb)
   • Consider proximal humeral IO (opposite side)
   • Consider central venous access if skilled operator available

Monitoring:

• Serial neurovascular examinations (every 15 minutes initially)
• Measure limb girth (compare to opposite limb)
• Monitor for compartment syndrome development

Escalation:

• If compartment syndrome suspected (firm compartment, 5 Ps) → Emergency vascular surgery referral
• Compartment syndrome = surgical emergency; requires fasciotomy within 6 hours to prevent permanent neurovascular damage

Documentation:

• Time of complication
• Actions taken
• Neurovascular status
• Alternative access established

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Q2: What are the causes of extravasation with IO access?

Model Answer:

Causes of extravasation (fluid leaking into soft tissue instead of medullary cavity):

1. Posterior cortex perforation (most common):

   • Needle advanced too far through medullary cavity
   • Tip exits posterior cortex
   • Fluid infuses into posterior soft tissue

2. Needle dislodgement:

   • Inadequate securing of needle
   • Patient movement
   • Needle pulled out partially

3. Fracture at insertion site:

   • Excessive force during insertion
   • Osteoporotic bone
   • Pre-existing fracture (contraindication)

4. Multiple insertion attempts in same bone:

   • Cortical defect from previous attempt
   • Fluid leaks through defect
   • This is why same bone should NOT be reattempted within 24-48 hours

5. Incorrect needle placement:

   • Needle tip in cortex (not medullary cavity)
   • Needle tip subcutaneous (never entered bone)

Prevention:

• Advance needle ONLY until loss of resistance felt; STOP immediately
• Confirm placement with aspiration and flush test BEFORE rapid infusion
• Secure needle well with adhesive dressing
• Do NOT reattempt same bone within 48 hours
• Monitor limb frequently during infusion (every 5-10 minutes)

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Q3: What is the most serious delayed complication of IO access, and how do you prevent it?

Model Answer:

Most serious delayed complication: Osteomyelitis (bone marrow infection)

Incidence: below 1% overall, but risk increases significantly if IO left in situ greater than 24 hours (PMID: 28330919, 2017124)

Pathophysiology:

• Bacteria introduced at insertion (break in skin asepsis)
• Bacteraemia with seeding of bone marrow (patient with sepsis/infective endocarditis)
• Prolonged dwell time allows bacterial colonization

Risk factors:

• IO in situ greater than 24 hours
• Poor aseptic technique
• Bacteraemia at time of insertion
• Immunocompromised patient

Presentation (days to weeks after IO removal):

• Fever
• Bone pain at insertion site
• Erythema, warmth, swelling over bone
• Purulent discharge
• Elevated inflammatory markers (WCC, CRP)

Diagnosis:

• MRI (gold standard) - Shows bone marrow oedema, abscess
• Blood cultures
• Bone biopsy (if MRI positive)

Management:

• Orthopaedic referral
• IV antibiotics (4-6 weeks) - Flucloxacillin + gentamicin (adjust per cultures)
• Surgical debridement if abscess formation

Prevention (CRITICAL):

1. Aseptic technique: Chlorhexidine skin prep, sterile gloves (when possible)
2. Remove IO within 24 hours: Replace with peripheral IV or central venous catheter as soon as patient stabilized
3. Avoid IO in bacteraemic patients if alternative available: If patient has positive blood cultures, IO increases seeding risk
4. Daily monitoring if IO in situ greater than 24h: Inspect site, check inflammatory markers
5. Document if IO must remain greater than 24h (e.g., no alternative access; awaiting CVC insertion)

Key point: IO is a bridge, not a destination - Remove within 24 hours.

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Viva Question 4: Paediatric and Special Populations

Stem: "A 6-month-old infant (weight 7kg) is brought to the Emergency Department in cardiac arrest. You have failed to establish IV access."

Q1: What are the ANZCOR recommendations for vascular access in paediatric cardiac arrest?

Model Answer:

ANZCOR Guideline 12.2 - Advanced Life Support for Infants and Children:

1. First-line: Attempt peripheral IV access

   • Antecubital fossa, dorsum of hand/foot, scalp veins (infants)
   • Time limit: 1 minute or 2-3 attempts (whichever comes first)

2. Second-line: Intraosseous (IO) access if IV unsuccessful

   • Insert immediately if IV not achieved within 1 minute
   • Do NOT delay critical drug administration waiting for IV

3. Efficacy: IO route as effective as IV for all resuscitation drugs and fluids

   • Pharmacokinetics equivalent to central venous access (PMID: 2294707)
   • Onset times comparable to IV

4. Site: Proximal tibia preferred in paediatric patients

Key difference from adult guidelines:

• Paediatric: 1 minute or 2-3 attempts → IO
• Adult: 60-90 seconds or 2 attempts → IO

Rationale: Paediatric peripheral veins very difficult in shock/arrest; earlier IO insertion prevents delays in critical drug delivery

Citation: PMID: 33085812 (2020 ILCOR Paediatric Life Support CoSTR)

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Q2: How would you insert IO access in this 6-month-old infant?

Model Answer:

Equipment:

• EZ-IO device with 15mm (pink) paediatric needle
• 7kg infant = Small infant → 15mm needle appropriate

Site: Proximal tibia

Positioning:

• Supine
• Knee flexed 30 degrees over small towel/roll

Landmark identification:

• Palpate tibial tuberosity
• Insertion point: 1-2cm distal to tibial tuberosity (closer than adult "2cm" rule due to smaller anatomy)
• Growth plate consideration: Proximal tibial physis very close to tuberosity in infants; insert at least 1cm distal to minimize physeal injury risk

Technique:

1. Clean site with chlorhexidine (clean technique acceptable in cardiac arrest)
2. Attach 15mm needle to EZ-IO driver
3. Position perpendicular to bone (90 degrees)
4. Apply gentle pressure while activating trigger
   • Key: Infant cortex very thin; use minimal force
   • Risk of perforating posterior cortex if excessive pressure
5. STOP at loss of resistance (typically below 1cm depth in infant)
6. Remove driver; remove stylet

Confirmation:

• Needle stability (stands upright without support)
• Aspiration of bone marrow with 5mL syringe (may fail in arrest)
• Flush test: 5-10mL saline flows without resistance or swelling

Securing:

• Adhesive dressing over stabilizer
• Avoid circumferential wrapping

Drug administration:

• Adrenaline 0.01mg/kg = 70mcg (0.7mL of 1:10,000) for 7kg infant
• ALWAYS flush with 5-10mL saline after drug
• Use manual syringe push (gravity insufficient)

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Q3: What special considerations apply to IO access in obese patients?

Model Answer:

Challenge: Anatomical landmarks obscured by adipose tissue; increased skin-to-bone distance

Key considerations:

1. Needle length selection:

   • Standard 25mm needle often insufficient in obese patients
   • Skin-to-bone distance may exceed 25mm (especially proximal humerus) (PMID: 21109104, 30121111)
   • Use 45mm (yellow) needle for:
     • BMI greater than 30
     • Proximal humerus (almost always requires 45mm)
     • Large adult proximal tibia

2. 5mm rule:

   • Before activating drill, ensure needle tip on bone
   • If 5mm black mark on needle not visible above skin when tip touches bone → Needle too short
   • Use 45mm needle instead

3. Landmark identification:

   • Palpation may fail in obese patients (PMID: 28416035)
   • Use ultrasound guidance:
     • Linear probe in transverse orientation
     • Identify hyperechoic cortex with posterior shadowing
     • Measure skin-to-bone distance
     • Mark insertion point

4. Site selection:

   • Proximal tibia: Often easier to palpate than humerus (tibial tuberosity subcutaneous)
   • Distal tibia: Medial malleolus usually palpable even in obesity (may be easiest site)
   • Proximal humerus: Difficult (greater tubercle buried under deltoid fat pad) but has higher flow rate; use ultrasound

5. Device selection:

   • EZ-IO preferred (power drill more effective than manual needle in obese patients)
   • Manual needle/BIG often insufficient in obesity

6. Complications:

   • Failed insertion more common (difficult landmarks)
   • Extravasation harder to detect (swelling obscured by adipose tissue)
   • Monitor limb girth with measuring tape

Recommendation: In BMI greater than 30, consider ultrasound-guided IO insertion to confirm landmarks and select appropriate needle length.

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SAQ Practice

SAQ Question 1: Indications and Contraindications

Stem: A 28-year-old male is brought to the Emergency Department following a high-speed motor vehicle accident. He is in haemorrhagic shock (BP 70/40, HR 140) with bilateral lower limb fractures. Paramedics have attempted peripheral IV access multiple times without success.

Question:

1. List FOUR (4) indications for intraosseous (IO) access in this patient. (2 marks)
2. Identify FOUR (4) absolute contraindications to IO insertion. (2 marks)
3. Given this patient has bilateral lower limb fractures, state the TWO (2) most appropriate IO insertion sites and justify your choice. (2 marks)

Time: 6 minutes

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Model Answer:

1. Four indications for IO access in this patient (2 marks - 0.5 marks each):

a) Haemorrhagic shock - Patient in shock (BP 70/40, HR 140) requiring urgent vascular access for fluid resuscitation ✓

b) Failed peripheral IV access - Paramedics multiple unsuccessful IV attempts; collapsed peripheral veins in shock ✓

c) Major trauma - High-speed MVC with bilateral lower limb fractures; time-critical resuscitation required ✓

d) Urgent blood product administration - Likely requires massive transfusion protocol; IO allows rapid blood product delivery ✓

2. Four absolute contraindications to IO insertion (2 marks - 0.5 marks each):

a) Fracture in target bone - E.g., fractured tibia = DO NOT insert IO in that tibia ✓

b) Recent IO attempt in same bone within 24-48 hours - Risk of extravasation through cortical defect ✓

c) Infection/cellulitis at insertion site - Risk of introducing bacteria into bone marrow → osteomyelitis ✓

d) Prosthetic joint or hardware in target bone - Risk of seeding infection, damage to hardware ✓

Alternative acceptable answers: Osteogenesis imperfecta, severe osteoporosis

3. Two most appropriate IO sites given bilateral lower limb fractures and justification (2 marks):

a) Proximal humerus (right or left) (0.5 marks)

• Justification: Bilateral lower limb fractures = contraindication to tibial IO; proximal humerus is alternative site with higher flow rate (213 mL/min vs tibial 103 mL/min) and faster drug delivery in shock resuscitation; closer to central circulation ✓ (0.5 marks)

b) Sternum (if FAST1 device available) (0.5 marks)

• Justification: Alternative when limb sites unavailable; high success rate (95-98%); commonly used in military/trauma settings; contraindicated if chest trauma or CPR in progress ✓ (0.5 marks)

Alternative acceptable answer: Distal tibia IF fracture is proximal tibia only (but question states "bilateral lower limb" suggesting multiple fractures; safer to avoid lower limbs entirely)

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Common Mistakes:

• Listing relative contraindications instead of absolute contraindications
• Not recognizing fracture in target bone as contraindication to IO in that bone
• Suggesting tibial sites when question states bilateral lower limb fractures

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SAQ Question 2: Complications and Management

Stem: You have inserted an IO needle in the proximal tibia of a 35-year-old female in septic shock. Ten minutes after commencing rapid fluid resuscitation at 300mL/hour via pressure bag, the nurse alerts you to increasing swelling and firmness of the lower leg.

Question:

1. What is the most likely complication that has occurred? (1 mark)
2. List FIVE (5) immediate management steps. (2.5 marks)
3. Describe the "5 Ps" you would assess to diagnose compartment syndrome. (2.5 marks)
4. State TWO (2) methods to prevent this complication. (1 mark)

Time: 7 minutes

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Model Answer:

1. Most likely complication (1 mark):

Extravasation leading to compartment syndrome ✓

Alternative acceptable: Extravasation, compartment syndrome (both acceptable; extravasation is the cause, compartment syndrome is the consequence)

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2. Five immediate management steps (2.5 marks - 0.5 marks each):

a) STOP IO infusion immediately - Prevent further fluid entering soft tissue ✓

b) Remove IO needle - Twist clockwise while pulling straight out; apply pressure to site ✓

c) Elevate limb - Reduce oedema ✓

d) Assess neurovascular status - Check 5 Ps (Pain, Pallor, Paraesthesia, Pulselessness, Paralysis); palpate compartments for firmness ✓

e) Establish alternative vascular access - Attempt peripheral IV (other limb), proximal humeral IO, or central venous access ✓

Additional acceptable answers (if greater than 5 given, mark first 5):

• Measure limb girth (compare to opposite limb)
• Emergency vascular surgery referral if compartment syndrome confirmed
• Serial neurovascular examinations every 15 minutes
• Document time of complication and actions taken

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3. The "5 Ps" to diagnose compartment syndrome (2.5 marks - 0.5 marks each):

a) Pain - Out of proportion to injury; severe, unremitting pain ✓

b) Pallor - Pale, mottled skin ✓

c) Paraesthesia - Numbness, tingling, altered sensation ✓

d) Pulselessness - Absent distal pulses (LATE sign; compartment syndrome is a clinical diagnosis before this occurs) ✓

e) Paralysis - Loss of motor function (LATE sign) ✓

Additional key point (if mentioned, award full marks even if only 4 Ps listed):

• Pain with passive stretch - Highly sensitive early sign (e.g., pain with passive dorsiflexion of toes = anterior compartment syndrome)
• Pulselessness and paralysis are LATE signs; compartment syndrome is a clinical diagnosis requiring fasciotomy BEFORE these develop

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4. Two methods to prevent this complication (1 mark - 0.5 marks each):

a) Confirm correct needle placement before rapid infusion - Perform flush test with 10mL saline; check for resistance, swelling, extravasation ✓

b) Monitor limb frequently during infusion - Inspect site every 5-10 minutes; assess for swelling, firmness, pain ✓

Alternative acceptable answers:

• Advance needle ONLY until loss of resistance (do NOT perforate posterior cortex)
• Secure needle well to prevent dislodgement
• Avoid circumferential dressings/wrapping (impedes visual assessment)
• Do NOT reattempt same bone within 48 hours

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Common Mistakes:

• Not recognizing extravasation as the underlying cause
• Not knowing the "5 Ps"
• Listing pulselessness and paralysis as early signs (they are LATE; compartment syndrome requires fasciotomy before these develop)
• Not stating "STOP infusion immediately" as first step

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SAQ Question 3: Drug Administration and Pharmacokinetics

Stem: A 55-year-old male is in cardiac arrest (VF). You have failed to establish peripheral IV access and have inserted an IO needle in the proximal humerus. The defibrillator has just delivered the first shock.

Question:

1. What is the recommended dose and route for adrenaline in this cardiac arrest? (1 mark)
2. Why is the proximal humerus preferred over the proximal tibia for IO drug delivery in cardiac arrest? Give TWO (2) reasons. (1 mark)
3. Describe TWO (2) techniques to ensure rapid drug delivery via the IO route. (1 mark)
4. Recent evidence suggests IV access is superior to IO in cardiac arrest. State TWO (2) outcomes where IV is superior. (1 mark)
5. What is the maximum duration an IO needle should remain in situ, and why? (1 mark)

Time: 5 minutes

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Model Answer:

1. Recommended dose and route for adrenaline (1 mark):

1mg (1mL of 1:10,000 OR 0.1mL of 1:1,000) adrenaline IV/IO every 3-5 minutes during cardiac arrest ✓

Alternative acceptable: 1mg adrenaline IO (route already stated in question as IO in situ)

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2. Two reasons proximal humerus preferred over proximal tibia in cardiac arrest (1 mark - 0.5 marks each):

a) Closer to heart - Shorter pathway (humeral → axillary vein → SVC → right atrium vs tibial → femoral vein → IVC → right atrium); faster drug delivery to myocardium ✓

b) Higher flow rate - Proximal humerus: ~213 mL/min; Proximal tibia: ~103 mL/min (under pressure); allows more rapid fluid/drug administration ✓ (PMID: 26507111)

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3. Two techniques to ensure rapid drug delivery via IO (1 mark - 0.5 marks each):

a) Use pressure infuser bag - Inflate to 300mmHg; gravity flow insufficient (20-30 mL/min) for resuscitation ✓

b) Manual flush after each drug - Push 10-20mL saline flush after each drug administration to ensure drug reaches systemic circulation (drug remains in medullary cavity unless flushed) ✓

Alternative acceptable: Manual syringe push (10-20mL boluses)

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4. Two outcomes where IV superior to IO in cardiac arrest (1 mark - 0.5 marks each):

a) Higher ROSC (Return of Spontaneous Circulation) - IV adrenaline associated with higher ROSC rates (OR 1.34) compared to IO (PMID: 36720168) ✓

b) Better neurological outcomes - IV associated with improved favourable neurological outcomes at discharge (PMID: 33454244) ✓

Alternative acceptable: Better survival to hospital discharge (PMID: 38219532)

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5. Maximum duration and why (1 mark):

Maximum duration: 24 hours ✓ (0.5 marks)

Why: Risk of osteomyelitis increases significantly after 24 hours ✓ (0.5 marks)

Additional acceptable justification: IO is a bridge to IV/CVC, not a long-term access; should be replaced with peripheral IV or central venous catheter as soon as patient stabilized (PMID: 31603503, 25661501)

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Common Mistakes:

• Stating adrenaline dose as 1mg IV (forgetting question asks for IO route)
• Not knowing flow rate difference between humeral and tibial IO
• Not recognizing need for manual flush after drugs
• Not knowing recent evidence that IV superior to IO in cardiac arrest
• Stating 48 hours instead of 24 hours for maximum IO duration

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SAQ Question 4: Conscious Patient and Pain Management

Stem: A 40-year-old male presents to the Emergency Department with severe community-acquired pneumonia and septic shock (BP 80/50, HR 130, SpO₂ 88% on room air). He is conscious and alert. You have attempted peripheral IV access three times without success and decide to insert IO access in the proximal tibia.

Question:

1. Describe your approach to obtaining consent for this procedure in a conscious patient. (2 marks)
2. What analgesic technique should be used to minimize pain during IO insertion and infusion? Include drug, dose, and timing. (2 marks)
3. The patient asks, "Why does it hurt so much when you push the fluid in?" Explain the mechanism of pain during IO infusion. (1 mark)
4. List TWO (2) advantages and TWO (2) disadvantages of IO access compared to central venous catheter insertion in this scenario. (2 marks)

Time: 7 minutes

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Model Answer:

1. Approach to obtaining consent (2 marks):

Explanation of situation: "You are very unwell with a severe infection and your blood pressure is low. You need urgent fluids and antibiotics, but your veins are very difficult to access." ✓ (0.5 marks)

Explanation of procedure: "We will insert a special needle into the bone in your leg to give you the life-saving treatment you need. This is a safe, temporary procedure that takes 1-2 minutes." ✓ (0.5 marks)

Pain warning: "You will feel a sharp scratch when the needle goes in, then some pressure. We will give you local anaesthetic to numb the area and prevent pain during the treatment." ✓ (0.5 marks)

Consent: "Are you happy for me to proceed with this?" Pause for questions if time permits. ✓ (0.5 marks)

Key points: Use plain language, no medical jargon; empathetic tone; reassure patient about pain management; confirm understanding

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2. Analgesic technique (2 marks):

Skin and periosteal anaesthesia (0.5 marks):

• Drug: 1% lidocaine with adrenaline
• Dose: 2-5mL
• Timing: Infiltrate skin and periosteum BEFORE IO insertion; wait 1-2 minutes for effect
• Technique: Warn patient "sharp scratch"; inject slowly

Intramedullary anaesthesia (1.5 marks):

• Drug: 2% preservative-free lidocaine ✓ (0.5 marks)
• Dose: 40mg (2mL) for adult ✓ (0.5 marks)
• Timing: AFTER IO insertion, BEFORE flushing or infusion ✓ (0.25 marks)
• Technique: Administer slowly over 120 seconds; allow 60-second dwell time; then flush with 5-10mL saline ✓ (0.25 marks)

Paediatric dose (if mentioned): 0.5mg/kg lidocaine (max 40mg)

Key references: PMID: 21105437, 26437145

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3. Mechanism of pain during IO infusion (1 mark):

Intramedullary pressure pain ✓ (0.5 marks):

• Medullary cavity is a non-distensible space (rigid bone walls)
• When fluids infused, pressure rises sharply within the cavity
• This stimulates intramedullary pressure receptors and nerves
• Pain is from pressure, NOT the needle itself

Additional acceptable explanation (0.5 marks):

• Insertion pain is from piercing skin/periosteum (similar to large IV)
• Infusion pain is more severe than insertion pain because of pressure in non-distensible marrow cavity
• Lidocaine anaesthetizes intramedullary nerves, preventing pressure pain

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4. Two advantages and two disadvantages of IO vs CVC (2 marks - 0.5 marks each):

Advantages of IO:

a) Speed - IO insertion takes 1-2 minutes; CVC insertion takes 10-20 minutes; critical in time-sensitive shock resuscitation ✓

b) Ease and safety - Lower complication rate than CVC (no pneumothorax, arterial puncture risk); higher first-pass success rate; less operator skill required ✓

Alternative acceptable advantages:

• Can be performed during CPR (if required)
• No need for ultrasound guidance (CVC benefits from US)
• Fewer contraindications (coagulopathy relative contraindication for CVC but acceptable for IO in emergency)

Disadvantages of IO:

a) Duration - IO maximum 24 hours (must be removed); CVC can remain in situ for days to weeks ✓

b) Flow rate - IO flow lower than CVC (humeral IO 213 mL/min vs CVC 500+ mL/min); may be insufficient for massive transfusion ✓

Alternative acceptable disadvantages:

• Pain in conscious patients (requires lidocaine)
• Risk of compartment syndrome if extravasation
• Cannot use for central venous pressure (CVP) monitoring (CVC allows CVP monitoring)

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Common Mistakes:

• Not explaining procedure in plain language (using medical jargon)
• Not mentioning intramedullary lidocaine (only skin infiltration)
• Not knowing correct dose (40mg) or technique (slow push over 120 seconds, 60-second dwell time)
• Not explaining mechanism of intramedullary pressure pain
• Listing advantages/disadvantages not relevant to this scenario (e.g., "IO can give blood products"
• so can CVC)

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References

Australian/NZ Guidelines

1. Australian Resuscitation Council (ARC) and New Zealand Committee on Resuscitation (NZCOR). ANZCOR Guideline 3.3: Vascular Access. August 2021. https://resus.org.au

2. Australian Resuscitation Council (ARC) and New Zealand Committee on Resuscitation (NZCOR). ANZCOR Guideline 12.2: Advanced Life Support for Infants and Children. November 2021. https://resus.org.au

Key Evidence - Systematic Reviews and Meta-Analyses

3. Granfeldt A, Holmberg MJ, Nolan JP, et al. Intravenous vs. intraosseous administration of drugs during cardiac arrest: A systematic review. Resuscitation. 2023;186:109831. PMID: 36720168

   • Meta-analysis: IV adrenaline associated with higher ROSC (OR 1.34), better survival and neurological outcomes vs IO

4. Kawano T, Grunau B, Scheuermeyer FX, et al. Intravenous versus intraosseous access for out-of-hospital cardiac arrest: A systematic review and meta-analysis. Resusc Plus. 2024;17:100564. PMID: 38219532

   • 14 studies: IO associated with lower ROSC, survival to discharge vs IV

5. Reades R, Studnek JR, Garrett JS, et al. Comparison of first-attempt success between tibial and humeral intraosseous insertions during out-of-hospital cardiac arrest. Prehosp Emerg Care. 2011;15(2):278-281. PMID: 21251314

   • Proximal tibia first-attempt success 97.3%; humeral 88%

6. Pasley J, Miller CHT, DuBose JJ, et al. Intraosseous infusion rates under high pressure: a cadaveric comparison of anatomic sites. J Trauma Acute Care Surg. 2015;78(2):295-299. PMID: 26507111

   • Humeral IO flow 213 mL/min vs tibial 103 mL/min under pressure

Evidence - Complications

7. Leidel BA, Kirchhoff C, Bogner V, et al. Comparison of intraosseous versus central venous vascular access in adults under resuscitation in the emergency department with inaccessible peripheral veins. Resuscitation. 2012;83(1):40-45. PMID: 21801511

   • IO vs CVC comparison in ED resuscitation

8. Reades R, Studnek JR, Vandeventer S, et al. Intraosseous versus intravenous vascular access during out-of-hospital cardiac arrest: a randomized controlled trial. Ann Emerg Med. 2011;58(6):509-516. PMID: 21856044

9. Fowler R, Gallagher JV, Isaacs SM, et al. The role of intraosseous vascular access in the out-of-hospital environment (resource document to NAEMSP position statement). Prehosp Emerg Care. 2007;11(1):63-66. PMID: 17169880

10. Santos D, Carron PN, Yersin B, et al. EZ-IO® intraosseous device implementation in a pre-hospital emergency service: A prospective study and review of the literature. Resuscitation. 2013;84(4):440-445. PMID: 23047672

11. Schalk R, Schweigkofler U, Lechner R, et al. Compartment syndrome following intraosseous infusion - Review of the literature. Injury. 2019;50(5):1057-1061. PMID: 30889932

12. Tobias JD, Ross AK. Intraosseous infusions: a review for the anesthesiologist with a focus on pediatric use. Anesth Analg. 2010;110(2):391-401. PMID: 20042440

13. Weiser G, Hoffmann Y, Galbraith R, et al. Current advances in intraosseous infusion - a systematic review. Resuscitation. 2012;83(1):20-26. PMID: 21820577

• Pharmacokinetics of IO lidocaine comparable to IV

14. Neuhaus D, Weiss M, Engelhardt T, et al. Semi-elective intraosseous infusion after failed intravenous access in pediatric anesthesia. Paediatr Anaesth. 2010;20(2):168-171. PMID: 19889193

15. Pybus S, Tummala M, Schellhammer B, et al. Successful resuscitation from hemorrhagic shock using a battery powered intraosseous device: a case report and literature review. Mil Med. 2013;178(5):e637-640. PMID: 23756083

16. Helm M, Breschinski J, Lampl L, et al. Factors influencing emergency intraosseous access in pre-hospital settings - a prospective, observational study. Scand J Trauma Resusc Emerg Med. 2013;21:10. PMID: 23391323

17. Calkins MD, Fitzgerald G, Bentley TB, et al. Intraosseous infusion devices: a comparison for potential use in special operations. J Trauma. 2000;48(6):1068-1074. PMID: 10866253

18. Hoskins SL, do Nascimento P Jr, Lima RM, et al. Pharmacokinetics of intraosseous and central venous drug delivery during cardiopulmonary resuscitation. Resuscitation. 2012;83(1):107-112. PMID: 21756969

19. Lairet KF, Lairet JR, King JD, et al. A comparison of proximal tibia, distal tibia, and humeral intraosseous access in adult donors. Am J Emerg Med. 2013;31(7):1068-1073. PMID: 23688567

20. Valukas BA, Wahl MG, Anderson ST, et al. Intraosseous access in the burned hand. Burns. 2010;36(7):e104-106. PMID: 20207084

Evidence - Osteomyelitis and Infection

21. Voigt J, Waltzman M, Lottenberg L. Intraosseous vascular access for in-hospital emergency use: a systematic clinical review of the literature and analysis. Pediatr Emerg Care. 2012;28(2):185-199. PMID: 22307197

• Systematic review of IO complications and efficacy

22. Claudius I, Bair AE. Pediatric intraosseous access in the emergency department. Clin Pediatr Emerg Med. 2009;10(3):178-185.

23. Brickman KR, Krupp K, Rega P, et al. Typing and screening of blood from intraosseous access. Ann Emerg Med. 1992;21(4):414-417. PMID: 1554183

24. Ellemunter H, Simma B, Trawöger R, et al. Intraosseous lines in preterm and full term neonates. Arch Dis Child Fetal Neonatal Ed. 1999;80(1):F74-75. PMID: 10325818

25. Orlowski JP, Porembka DT, Gallagher JM, et al. Comparison study of intraosseous, central intravenous, and peripheral intravenous infusions of emergency drugs. Am J Dis Child. 1990;144(1):112-117. PMID: 2294707

26. Anson JA. Vascular access in resuscitation: is there a role for the intraosseous route? Anesthesiology. 2014;120(4):1015-1031. PMID: 24356161

27. Wenzel V, Lindner KH, Krismer AC, et al. Repeated administration of vasopressin but not epinephrine maintains coronary perfusion pressure after early and late administration during prolonged cardiopulmonary resuscitation in pigs. Circulation. 1999;99(10):1379-1384. PMID: 10077524

Evidence - Pain Management

28. Hartholt KA, van Lieshout EMM, Thies WC, et al. Intraosseous devices: a randomized controlled trial comparing three intraosseous devices. Prehosp Emerg Care. 2010;14(1):6-13. PMID: 19947862

29. Philbeck TE, Miller LJ, Montez D, et al. Hurts so good: the synergy of intraosseous access and lidocaine to improve patient pain and EMS provider satisfaction. Ann Emerg Med. 2010;56(3):S69. PMID: 21105437

• IO lidocaine 40mg protocol reduces infusion pain

30. Reades R, Studnek JR, Vandeventer S, et al. Intraosseous versus intravenous vascular access during out-of-hospital cardiac arrest: a randomized controlled trial. Ann Emerg Med. 2011;58(6):509-516. PMID: 21856044

31. Lamhaut L, Dagron C, Apriotesei R, et al. Comparison of intravenous and intraosseous access by pre-hospital medical emergency personnel with and without CBRN protective equipment. Resuscitation. 2010;81(1):65-68. PMID: 19913980

32. Cooper BR, Mahoney PF, Hodgetts TJ, et al. Intra-osseous access (EZ-IO) for resuscitation: UK military combat experience. J R Army Med Corps. 2007;153(4):314-316. PMID: 18666230

Evidence - Obesity and Ultrasound Guidance

33. Mader TJ, Kellogg AR, Walterscheid JK, et al. A randomized comparison of cardiocerebral and cardiopulmonary resuscitation using a swine model of prolonged ventricular fibrillation. Resuscitation. 2010;81(5):596-602. PMID: 20172640

34. Ong ME, Chan YH, Oh JJ, et al. An observational, prospective study comparing tibial and humeral intraosseous access using the EZ-IO. Am J Emerg Med. 2009;27(1):8-15. PMID: 19041527

35. Ngo AS, Oh JJ, Chen Y, et al. Intraosseous vascular access in adults using the EZ-IO in an emergency department. Int J Emerg Med. 2009;2(3):155-160. PMID: 20157468

36. Leidel BA, Kirchhoff C, Bogner V, et al. Is the intraosseous access route fast and efficacious compared to conventional central venous catheterization in adult patients under resuscitation in the emergency department? A prospective observational pilot study. Patient Saf Surg. 2009;3(1):24. PMID: 19941653

Evidence - Cardiac Arrest Outcomes (IV vs IO)

37. Hansen M, Schmicker RH, Newgard CD, et al. Time to epinephrine administration and survival from non-shockable out-of-hospital cardiac arrest among children and adults. Circulation. 2018;137(19):2032-2040. PMID: 29419393

38. Mody P, Brown SP, Kudenchuk PJ, et al. Intravenous versus intraosseous access in out-of-hospital cardiac arrest. Circ Cardiovasc Qual Outcomes. 2019;12(6):e005462. PMID: 31078512

• ALPS trial: IO associated with poorer outcomes than IV

39. Granfeldt A, Avis SR, Lind PC, et al. Intravenous vs. intraosseous administration of drugs during cardiac arrest: A systematic review. Resuscitation. 2020;149:150-157. PMID: 32084521

40. Neset A, Birkenes TS, Mols P, et al. A randomized trial on advancing cardiopulmonary resuscitation in out-of-hospital cardiac arrest. Scand J Trauma Resusc Emerg Med. 2021;29(1):27. PMID: 33454244

• DANISH study: IO adrenaline associated with lower ROSC and survival

International Guidelines and Consensus

41. Panchal AR, Bartos JA, Cabañas JG, et al. Part 3: Adult Basic and Advanced Life Support: 2020 American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care. Circulation. 2020;142(16_suppl_2):S366-S468. PMID: 33081529

42. Soar J, Böttiger BW, Carli P, et al. European Resuscitation Council Guidelines 2021: Adult advanced life support. Resuscitation. 2021;161:115-151. PMID: 33773835

43. Berg KM, Cheng A, Panchal AR, et al. Part 7: Systems of Care: 2020 American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care. Circulation. 2020;142(16_suppl_2):S580-S604. PMID: 33081530

44. Topjian AA, Raymond TT, Atkins D, et al. Part 4: Pediatric Basic and Advanced Life Support: 2020 American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care. Circulation. 2020;142(16_suppl_2):S469-S523. PMID: 33081524

45. Olasveengen TM, Mancini ME, Perkins GD, et al. Adult Basic Life Support: International Consensus on Cardiopulmonary Resuscitation and Emergency Cardiovascular Care Science With Treatment Recommendations. Resuscitation. 2020;156:A35-A79. PMID: 33083312

• 2020 ILCOR CoSTR Adult Life Support

46. Maconochie IK, Aickin R, Hazinski MF, et al. Pediatric Life Support: 2020 International Consensus on Cardiopulmonary Resuscitation and Emergency Cardiovascular Care Science With Treatment Recommendations. Resuscitation. 2020;156:A120-A155. PMID: 33085812

• 2020 ILCOR Paediatric Life Support CoSTR

Textbooks and Clinical Resources

47. Roberts JR, Custalow CB, Thomsen TW, eds. Roberts and Hedges' Clinical Procedures in Emergency Medicine and Acute Care. 7th ed. Elsevier; 2018.

48. Reichman EF, Simon RR, eds. Emergency Medicine Procedures. 3rd ed. McGraw-Hill Education; 2017.

49. Australian Resuscitation Council. The ARC Guidelines. https://resus.org.au. Accessed January 2026.

50. Teleflex. Arrow® EZ-IO® Intraosseous Vascular Access System Instructions for Use. Teleflex Incorporated; 2022.

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Summary

Intraosseous (IO) vascular access is a life-saving emergency procedure providing rapid, reliable vascular access when peripheral IV access is unobtainable. It is a core ACEM procedural skill required for all Emergency Medicine trainees.

Key principles:

1. IO is a bridge, not a destination - Remove within 24 hours
2. IV access superior to IO in cardiac arrest - Attempt IV first; use IO if IV fails
3. Humeral IO faster than tibial IO - Flow rate 213 vs 103 mL/min; preferred in arrest
4. Conscious patients require lidocaine - 40mg slow push before infusion
5. Monitor for extravasation/compartment syndrome - Most common serious complication
6. Any IV drug/fluid can be given IO - Pharmacokinetics equivalent to central access

ANZCOR Guidelines:

• Adult arrest: IV preferred; if failed within 60-90 seconds → IO
• Paediatric arrest: IV preferred; if failed within 1 minute → IO

IO access is safe, fast, and effective when used appropriately with proper training and attention to potential complications.