Intraosseous (IO) Access

Quick Reference

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ACEM Exam Focus

Primary Written & Viva

• Anatomy: Medullary cavity anatomy, cortical vs trabecular bone, growth plates in children
• Physiology: Marrow circulation, venous plexus drainage, pharmacokinetics via IO route (Tmax, Cmax comparable to IV)
• Pharmacology: Drug doses identical to IV, flush with 10 mL bolus after administration

Fellowship Written & OSCE

• Indications: When to use in cardiac arrest, trauma, burns, pediatric resuscitation
• Technique: Site selection, insertion technique, confirmation, troubleshooting
• Complications: Recognition and management of compartment syndrome, infection risk
• OSCE station: 11-minute procedural station with manikin, marking criteria focus on site selection, technique, confirmation

Key Exam Principles

1. IO is second-line to IV (ANZCOR: IV preferred, IO if IV cannot be rapidly achieved within 2 attempts)
2. All drugs and fluids can be given IO (including blood products, medications, contrast)
3. Pharmacokinetics comparable to IV (bioavailability greater than 95%, circulation time below 1 minute)
4. Maximum duration 24 hours (transition to IV/central access, remove to prevent infection)

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Key Points

Clinical Pearl: 1. Powered devices (EZ-IO) have 85-95% first-attempt success rate vs 70-80% for manual devices (PMID: 20947238, 35486486)

2. Proximal tibia is the default site in children and adults (easiest landmark, highest flow rates)
3. Humeral head provides faster central circulation time (2-4 seconds vs 6-10 seconds tibial) but requires anatomical knowledge (PMID: 29477251)
4. Aspirate marrow to confirm placement but absence does not mean failure (can still infuse)
5. Lidocaine 2% (20-40 mg) through IO before fluid bolus reduces pain in conscious patients (PMID: 25109750)
6. Complications are rare (below 1.2%) but include compartment syndrome, fracture (pediatric), osteomyelitis (greater than 24h use)
7. Remove and transition to IV within 24 hours to minimize infection risk (ANZCOR guideline)

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Epidemiology

Utilization

• Prehospital: 2-8% of emergency transports involve IO access (higher in cardiac arrest 15-30%)
• ED: 1-3% of resuscitation cases require IO access (PMID: 39480221)
• Pediatric: 3-5% of critically ill children receive IO in ED/prehospital (PMID: 37674559)

Success Rates by Device

Flow Rates

• Gravity flow: 50-125 mL/min (varies by site, bone density, age)
• Pressure bag (300 mmHg): 150-200 mL/min
• Push-pull technique: Up to 300 mL/min for rapid bolus
• Humeral site: 20-30% faster flow than tibial (PMID: 26278569)

Outcomes

• Survival: No significant difference in OHCA survival between IO vs IV access (PMID: 39480221, 37990950)
• Time to medication: IO achieves drug delivery 2-4 minutes faster when IV difficult (PMID: 40782513)
• Complication rate: 0.6-1.2% overall (PMID: 39645023)

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Pathophysiology

Medullary Circulation

Bone marrow anatomy:

• Cortical bone: Dense outer layer, drilled by IO needle
• Trabecular bone: Spongy inner medullary cavity, contains red/yellow marrow
• Venous sinusoids: Low-pressure vessels within medullary cavity, drain to central venous circulation
• Central venous drainage: Marrow vessels → nutrient veins → systemic venous return

Physiology of IO infusion:

1. Fluid enters medullary cavity under pressure
2. Displaces marrow into sinusoidal venous plexus
3. Drains via nutrient veins and emissary veins to central circulation
4. Central circulation time: 4-6 seconds humeral, 6-10 seconds tibial (PMID: 29477251)

Pharmacokinetics

Absorption and bioavailability:

• Bioavailability: greater than 95% (equivalent to IV for most drugs) (PMID: 30488015)
• Time to peak concentration (Tmax): Comparable to IV (within 1-2 minutes)
• Peak concentration (Cmax): 90-100% of IV levels for adrenaline, vasopressors, antibiotics

Drug compatibility:

• All IV medications can be given IO: Adrenaline, amiodarone, atropine, vasopressors, antibiotics, analgesics, sedatives
• Blood products: PRBCs, FFP, platelets (use pressure bag or push-pull technique)
• Contrast media: Safe for CT angiography (theoretical fat emboli concern not clinically significant)
• Flush required: 10 mL saline bolus after each drug to ensure delivery

Age-Related Changes

Pediatrics:

• Neonate/infant: Rich red marrow, rapid IO absorption, thin cortex (easier insertion, fracture risk)
• Child: Active growth plates (avoid epiphyseal injury), transition from red to yellow marrow

Adults:

• Young adult: Predominantly yellow marrow (fatty), still perfused and functional
• Elderly: Increased cortical thickness (harder insertion), reduced marrow perfusion (slower flow rates)
• Obese: Increased subcutaneous tissue, harder to identify landmarks

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Indications

Absolute Indications

1. Cardiac arrest (VF, VT, PEA, asystole) when IV access cannot be achieved within 2 attempts or 90 seconds (ANZCOR)
2. Life-threatening shock requiring immediate vascular access:
   • Septic shock with failed IV access
   • Hypovolemic shock (trauma, GI bleeding) with collapsed veins
   • Anaphylaxis requiring adrenaline when IV unobtainable
3. Status epilepticus with no IV access available
4. Severe burns (greater than 20% TBSA) with no IV access (veins thrombosed or inaccessible)

Relative Indications

1. Pediatric resuscitation: Failed IV access × 2 attempts in child below 6 years (small veins, difficult IV)
2. IV drug user (IVDU): Sclerosed veins, limited venous access
3. Obesity: Difficult IV access due to adipose tissue
4. Hypotension/shock: Collapsed peripheral veins
5. Edema: Massive peripheral edema obscuring veins (CHF, nephrotic syndrome)
6. Time-critical medication delivery: When delay in IV access would compromise care (e.g., peri-arrest)

When to Consider

ED scenarios:

• Cardiac arrest arrives without IV access
• Pediatric arrest or near-arrest (failed 2 IV attempts)
• Major trauma with hemorrhagic shock (femoral IV failed, veins collapsed)
• Burn patient requiring fluid resuscitation (peripheral veins destroyed)
• Septic shock with delayed IV access (trainee has attempted twice, IO faster than senior IV)

Prehospital scenarios:

• Rural/remote transfer without IV access
• RFDS retrieval requiring vascular access prior to transport
• Prolonged scene time with failed IV attempts (e.g., entrapment)

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Contraindications

Absolute

Relative

• Prosthetic joint or orthopedic hardware at or near site (may obstruct marrow cavity, infection risk)
• Osteogenesis imperfecta or osteoporosis (fracture risk)
• Recent orthopedic procedure at site (below 48 hours)
• Vascular injury proximal to insertion site (fluid may not reach central circulation)
• Inability to identify landmarks (obesity, edema) – risk of misplacement

Risk-Benefit Considerations

When relative contraindications may be acceptable:

• Life-threatening emergency: IO in limb with suspected fracture if no other access available (use contralateral limb if possible)
• Pediatric cardiac arrest: IO despite obesity or difficult landmarks (use ultrasound if available)
• Shock requiring immediate access: IO in edematous limb if alternative sites unsuitable

ANZCOR Guidance (Guideline 11.5):

• "IV access is preferred means of administering medications during cardiac arrest when compared to IO access"
• "If IV access cannot be rapidly achieved within 2 attempts, it is reasonable to consider IO access"

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Anatomy

Surface Landmarks

Proximal Tibia (Most Common Site)

Proximal Humerus (Alternative Site)

Distal Tibia (Pediatric Alternative)

Sternum (Adult Only, Specialized Device)

Deep Anatomy

Proximal tibia:

• Cortical thickness: 3-6 mm adults, 1-3 mm children
• Medullary cavity: 1-3 cm diameter, contains red/yellow marrow
• Structures at risk: Tibial nerve (posterior), popliteal vessels (posterior), growth plate (children)
• Safe zone: Anteromedial tibia (no major neurovascular structures)

Proximal humerus:

• Cortical thickness: 2-5 mm
• Medullary cavity: Large, rich marrow supply
• Structures at risk: Axillary nerve (inferior), radial nerve (posterior), brachial plexus (medial)
• Safe zone: Greater tuberosity (lateral aspect)

Anatomical Diagram

PROXIMAL TIBIA (Anteromedial View):

     Patella
        |
   Patellar tendon
        |
    [Tibial Tuberosity] ← Palpable landmark
        |
        | 2 cm distal
        v
     ★ INSERTION POINT (1-2 cm medial to midline)
        |
        | Insert perpendicular to bone
        v
    Anterior tibial surface


PROXIMAL HUMERUS (Lateral View):

    Acromion
        |
        | 2-3 cm inferior
        v
    [Greater Tuberosity] ← Palpable landmark
        |
     ★ INSERTION POINT (perpendicular, arm adducted)
        |
        v
    Humeral head
        |
    Surgical neck

Danger Zones

Anatomical Variants

1. Pediatric growth plates: Open epiphyseal plates in children – avoid inserting through growth plate (can cause fracture or growth arrest)
2. Obese patients: Thicker subcutaneous tissue obscures landmarks – may require longer needle (25 mm vs 15 mm)
3. Elderly: Increased cortical density (osteopetrosis), reduced marrow perfusion
4. Previous surgery: Orthopedic hardware, joint replacement may obstruct medullary cavity

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Equipment

Essential Equipment

EZ-IO Device (Vidacare/Teleflex) – Most Common

Alternative Devices

Optional Equipment

Equipment Sizing

Adult

Pediatric

Special Populations:

• Obese child: Use 25 mm needle if tissue depth greater than 1.5 cm
• Premature infant: Consider umbilical venous catheter instead of IO

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Preparation

Patient Preparation

1. Brief explanation (if conscious): "We need to place a needle in your bone to give you fluids and medications because your veins are difficult to access"
2. Positioning:
   • Proximal tibia: Supine, leg extended, support knee with towel
   • Humeral head: Supine, arm adducted across chest, hand on abdomen
   • Distal tibia: Supine or lateral, foot supported
3. Monitoring: Continuous ECG, SpO2, BP (if not already applied)
4. Analgesia (conscious patient): Consider procedural sedation or local anesthetic (lidocaine infiltration around site)

Operator Preparation

1. Standard precautions: Gloves, gown, mask, eye protection (splash risk)
2. Hand hygiene: Alcohol-based hand rub
3. Equipment check:
   • EZ-IO driver fully charged (green light)
   • Correct needle size selected (patient size, site)
   • Flush syringes prepared (10 mL NS × 2-3)
   • IV tubing connected and primed
4. Assistance arranged: Nurse to prepare drugs, second person to stabilize limb if needed
5. Backup plan identified: Alternative site if first attempt fails, IV access as backup

Site Preparation

1. Sterile technique: Clean (non-sterile) for cardiac arrest, aseptic (sterile) if time permits
2. Skin preparation:
   • Cardiac arrest: Rapid wipe with chlorhexidine 2% or alcohol swab (10 seconds)
   • Non-arrest: Chlorhexidine 2% (30 seconds scrub) or povidone-iodine 10% (2 minutes)
3. Draping: Sterile drape with fenestration (if time permits)

Positioning

Proximal tibia:

• Patient position: Supine, leg extended (knee straight or slightly flexed 10-20°)
• Operator position: Stand on side of leg, at level of knee
• Assistant: Stabilize leg if patient conscious or moving
• Landmark confirmation: Palpate tibial tuberosity, measure 2 cm distal and 1-2 cm medial

Proximal humerus:

• Patient position: Supine, arm adducted across chest, hand on opposite shoulder or abdomen
• Operator position: Stand on side of insertion, at level of shoulder
• Assistant: Stabilize shoulder and arm
• Landmark confirmation: Palpate greater tuberosity, ensure perpendicular angle

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Procedure Steps

Step-by-Step Technique (EZ-IO Device)

Step 1: Site Selection and Landmark Identification

Proximal tibia (default site):

1. Palpate patella and tibial tuberosity
2. Measure 2 cm (2 finger breadths) distal to tibial tuberosity
3. Move 1-2 cm medial (toward midline)
4. Palpate flat anteromedial tibial surface
5. Mark site with pen or thumbnail indentation

Key point: The insertion site should feel flat, not on the curved anterior surface of the tibia Common error: Inserting too lateral (on curved surface, needle may slip) or too proximal (risk of growth plate in pediatrics)

Step 2: Skin Preparation

1. Clean site with chlorhexidine 2% (30 seconds) or rapid alcohol wipe (cardiac arrest)
2. Allow to dry (chlorhexidine requires 30 seconds dry time for maximal effect)
3. Optional: Infiltrate skin with 1% lidocaine (1-2 mL SC) if conscious patient and time permits

Key point: In cardiac arrest, do not delay for sterile technique – rapid wipe and insert Common error: Excessive delay for sterile prep in time-critical situation

Step 3: Needle Preparation and Driver Attachment

1. Remove EZ-IO needle from package (check size: 15 mm pink, 25 mm blue, 45 mm yellow)
2. Attach needle to EZ-IO driver (twist clockwise until click)
3. Ensure driver is charged (green light when trigger pressed)
4. Prepare 10 mL syringe with normal saline for flush

Key point: Ensure needle is firmly attached (should not wobble) Common error: Loose needle attachment causes wobble and failed insertion

Step 4: Needle Insertion

1. Stabilize limb: Assistant or non-dominant hand stabilizes leg below insertion site
2. Position needle: Place needle tip perpendicular to bone (90° angle) at insertion site
3. Steady pressure: Apply firm downward pressure with dominant hand
4. Activate driver: Press trigger to activate drill (continuous pressure, do not "jab")
5. Drill until "pop": Continue drilling until sudden loss of resistance (5-10 seconds)
   • Pediatric: Very quick (2-5 seconds), thin cortex
   • Adult: 5-10 seconds
   • Elderly/osteopetrotic: 10-15 seconds, dense cortex
6. Stop drilling: Release trigger immediately after "pop" sensation
7. Unscrew driver: Twist counterclockwise to remove driver, leaving catheter in bone

Key point: Perpendicular insertion is critical (90° to bone surface) – angled insertion increases risk of bent needle or subperiosteal placement Common error: Angled insertion (causes needle to bend or slip off bone), excessive force (fracture risk), drilling too deep (posterior cortex penetration)

Step 5: Remove Stylet and Confirm Placement

1. Unscrew stylet: Twist inner stylet counterclockwise and remove (exposes catheter lumen)
2. Check stability: IO catheter should stand upright without support
3. Attach syringe: Connect 10 mL syringe to catheter hub
4. Aspirate marrow: Pull back on syringe – expect blood/marrow (dark red, thick)
   • Note: Absence of aspirate does NOT mean failure (marrow may be depleted in shock/arrest)
5. Flush test: If no aspirate, attempt flush with 5-10 mL saline
   • Success: Fluid flushes easily, no swelling or resistance
   • Failure: Resistance, visible swelling at insertion site (extravasation)

Key point: Marrow aspiration confirms placement but is not required for success (can proceed with flush test) Common error: Abandoning IO due to lack of aspirate (proceed with flush if catheter stable)

Step 6: Secure Catheter and Attach IV Tubing

1. Flush: Inject 10 mL normal saline to clear marrow debris from catheter
2. Attach IV extension tubing: Connect primed extension set to catheter hub
3. Secure with dressing: Apply transparent dressing or tape to stabilize catheter
   • Commercial stabilizer: EZ-Stabilizer or similar device
   • Alternative: Tape catheter hub to skin + bulky gauze around catheter
4. Document insertion time: Note time on dressing (remove within 24 hours)

Key point: Secure stabilization is critical – IO catheters are easily dislodged Common error: Inadequate stabilization causes catheter displacement during patient movement

Step 7: Administer Medications and Fluids

1. Initial flush: 10 mL NS bolus to confirm patency
2. Pain management (conscious patient): Lidocaine 2% (20-40 mg) through IO, wait 60 seconds before fluid bolus (PMID: 25109750)
3. Administer drugs: Give all medications as per IV protocol
4. Flush after each drug: 10 mL NS bolus after each medication
5. Fluid resuscitation:
   • Gravity flow: 50-125 mL/min
   • Pressure bag (300 mmHg): 150-200 mL/min
   • Push-pull technique: Rapid bolus (10-20 mL syringes, manual push)

Key point: Flush with 10 mL NS after every medication to ensure delivery to central circulation Common error: Forgetting flush (drug remains in catheter/medullary cavity)

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Confirmation of Success

If aspiration negative but flush positive: Proceed (marrow depletion common in shock/arrest) If aspiration negative AND flush difficult: Consider repositioning or alternative site

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Securing/Completion

Catheter stabilization:

1. Apply transparent dressing (Tegaderm) over insertion site
2. Secure catheter hub with tape or commercial stabilizer (EZ-Stabilizer)
3. Coil and tape IV extension tubing to limb
4. Document: Insertion time, site, needle size, ease of insertion, complications

Post-insertion monitoring:

• Inspect site every 15-30 minutes for swelling, erythema, extravasation
• Palpate surrounding tissue for firmness (compartment syndrome)
• Check distal perfusion (pulse, cap refill, sensation) if tibial site

Transition plan:

• Establish IV access as soon as feasible (IO is temporizing measure)
• Remove IO within 24 hours (infection risk increases after 24h)
• Document removal: Note time, appearance of site, any complications

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Ultrasound Guidance

When to Use

1. Difficult landmarks: Obesity (BMI greater than 40), massive edema, muscular body habitus
2. Anatomical uncertainty: Prior surgery, trauma, scarring
3. Pediatric: Confirm growth plate location (avoid epiphyseal injury)
4. Confirmation: Verify depth to cortex, ensure adequate needle length

Probe Selection

Technique

• Orientation: Transverse view (short-axis) to identify bone as hyperechoic line with posterior acoustic shadow
• Approach: Out-of-plane (needle perpendicular to probe) – visualize needle tip entering bone
• Key views:
  1. Pre-insertion: Measure depth from skin to cortex (select appropriate needle length)
  2. During insertion: Visualize needle tip penetrating cortex
  3. Post-insertion: Confirm catheter position, no fluid extravasation

Sonographic Anatomy

Proximal tibia:

• Cortex: Hyperechoic curved line (white)
• Posterior shadow: Dark shadow deep to cortex (bone absorbs ultrasound)
• Soft tissue: Hypoechoic muscle and subcutaneous fat above cortex

Proximal humerus:

• Humeral head: Hyperechoic rounded surface
• Greater tuberosity: Bony prominence lateral to humeral head
• Rotator cuff: Hyperechoic fibrillar tendons above bone

Pitfall: Periosteum can mimic cortex (appears hyperechoic) – ensure needle penetrates beyond periosteum into medullary cavity

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Alternative Techniques

Manual Needle (Jamshidi/Cook IO Needle)

• When to use: EZ-IO unavailable, battery failure, resource-limited settings
• Advantages: No battery required, inexpensive, widely available
• Disadvantages: Requires more force (fracture risk), longer insertion time (90-180 seconds), lower success rate (65-75%)
• Technique:
  1. Stabilize limb and identify landmarks as per powered device
  2. Insert needle perpendicular to bone with firm downward pressure
  3. Rotate needle clockwise while applying pressure (drilling motion)
  4. Continue until "pop" and loss of resistance
  5. Remove stylet and confirm as per EZ-IO

BIG (Bone Injection Gun) - Spring-Loaded

• When to use: Pediatric (age 3-12 years), powered device unavailable
• Advantages: Fast insertion (1-2 seconds), no battery required, high success in pediatrics
• Disadvantages: Loud "bang" (distressing), only pediatric sizes, single-use (cannot reposition)
• Technique:
  1. Load needle into BIG device (click into place)
  2. Position needle perpendicular to bone at insertion site
  3. Pull safety catch and press trigger (spring deploys needle into bone)
  4. Remove device, leaving catheter in bone
  5. Remove stylet and confirm

FAST1 (Sternal IO) - Adult Only

• When to use: Cardiac arrest (faster central circulation), supine patient, lower extremity injury/fracture
• Advantages: Fastest central circulation time (2-4 seconds), does not interfere with CPR, bilateral tibial fractures
• Disadvantages: Requires specialized device, adult only (manubrium too small in children), risk of mediastinal injury, patient discomfort
• Technique:
  1. Identify sternal notch and manubrium
  2. Position FAST1 introducer assembly on manubrium midline
  3. Press plunger to deploy needle into sternum (5-10 mm depth)
  4. Remove introducer, leaving catheter
  5. Confirm and flush

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Paediatric Considerations

Age-Specific Modifications

Neonate (below 1 month, below 3 kg)

Infant (1-12 months, 3-10 kg)

Child (1-12 years, 10-40 kg)

Adolescent (greater than 12 years, greater than 40 kg)

Equipment Sizing (Pediatric)

EZ-IO Needle Selection:

• below 3 kg: Manual needle 18G (consider UVC instead)
• 3-39 kg: 15 mm (pink) if tissue depth below 1.5 cm
• greater than 40 kg or obese: 25 mm (blue)

Technique Modifications

Insertion force:

• Infant/child: Light pressure (thin cortex perforates rapidly)
• Adolescent: Adult-level pressure

Drilling time:

• Infant: 2-5 seconds (very thin cortex)
• Child: 3-8 seconds
• Adolescent: 5-10 seconds (approaching adult cortical thickness)

Confirmation:

• Marrow aspiration: Less reliable in children (yellow marrow in older children, difficult to aspirate)
• Flush test: More important than aspiration in pediatrics

Pain management:

• Conscious child: Lidocaine 2% (0.5 mg/kg, max 20 mg) IO prior to fluid bolus
• Sedation: Consider procedural sedation (ketamine 1-2 mg/kg) if time permits

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Complications

Immediate Complications

Delayed Complications

Overall Complication Rates

Danish nationwide study (PMID: 39645023):

• Total complications: 0.6% (50/7,779 patients)
• Serious complications: 0.1% (osteomyelitis, fracture, compartment syndrome)
• Minor complications: 0.5% (local infection, pain, extravasation)
• Mortality: Not attributable to IO access (critically ill population)

Complication Prevention

Extravasation:

• Ensure perpendicular insertion (90° to bone)
• Confirm "pop" sensation before removing stylet
• Flush slowly (5-10 mL over 10-20 seconds) to assess for extravasation
• Monitor site during fluid administration (inspect every 15-30 minutes)

Compartment syndrome:

• Remove IO as soon as IV access established (minimize IO duration)
• Monitor distal perfusion (pulse, cap refill, sensation)
• Palpate compartment for firmness every 15-30 minutes
• Educate patient/family to report severe pain

Osteomyelitis:

• Remove IO within 24 hours maximum (infection risk increases after 24h)
• Use aseptic technique (chlorhexidine prep, sterile gloves if time permits)
• Avoid IO if cellulitis overlying site

Fracture (pediatric):

• Use appropriate needle size (15 mm for thin cortex)
• Light insertion pressure in infants/young children
• Stop drilling immediately after "pop" (do not overdrill)
• Avoid IO in bones with fractures or metabolic bone disease

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Troubleshooting

Rescue Techniques

If first IO attempt fails:

1. Attempt alternative site (e.g., if proximal tibia failed, try contralateral tibia or humeral head)
2. Do NOT reattempt same bone within 48 hours (cortical defect causes extravasation)
3. Switch to IV access if IO expertise unavailable or multiple failed attempts
4. Call for help: Senior clinician or retrieval team (RFDS) if rural/remote

If IO dislodges during use:

1. Remove IO immediately (do not reinsert into same site)
2. Apply pressure to site (5 minutes)
3. Attempt alternative site (contralateral limb or different bone)
4. Establish IV access if feasible

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Post-Procedure Care

Immediate Care

1. Flush catheter: 10 mL NS bolus after insertion, then after each medication
2. Monitor site: Inspect for swelling, erythema, extravasation every 15-30 minutes
3. Check distal perfusion: Pulse, capillary refill, sensation, motor function (if tibial site)
4. Secure catheter: Ensure stabilization device intact, catheter not dislodged
5. Documentation:
   • Date/time of insertion
   • Site (proximal tibia, humeral head, etc.)
   • Needle size (15/25/45 mm)
   • Ease of insertion (first attempt, complications)
   • Marrow aspiration (yes/no)
   • Medications/fluids administered
   • Anticipated removal time (within 24 hours)

Monitoring

Imaging Confirmation

Not routinely required (clinical confirmation sufficient)

Consider X-ray if:

• Uncertain placement (catheter unstable, difficult flush)
• Suspicion of fracture (pediatric, excessive force during insertion)
• Suspicion of posterior cortex perforation (drilled too deep)
• Persistent pain after removal (fracture, hematoma)

Documentation

Procedure note:

INDICATION: Cardiac arrest, failed IV access × 2 attempts
SITE: Right proximal tibia
DEVICE: EZ-IO 25 mm (blue) needle
TECHNIQUE: Aseptic technique, perpendicular insertion 2 cm distal to tibial tuberosity
CONFIRMATION: "Pop" sensation, catheter stable, marrow aspirated, 10 mL NS flush without resistance
COMPLICATIONS: None
PLAN: Transition to IV access when feasible, remove IO within 24 hours

Nursing documentation:

• Time of insertion (for 24-hour removal reminder)
• Site marked on patient (label or visible dressing)
• Medications/fluids administered via IO (document route "IO" not "IV")

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OSCE Practice

OSCE Station 1: Proximal Tibial IO Insertion (Procedural Station)

Format: Procedural skills assessment Time: 11 minutes Equipment: IO manikin (adult), EZ-IO driver, 25 mm needle, 10 mL syringes × 2, normal saline, gloves, skin prep, dressing

Candidate Instructions:

You are the emergency registrar. A 65-year-old male has suffered an out-of-hospital cardiac arrest. Your consultant has achieved ROSC after 10 minutes of CPR. The paramedics were unable to establish IV access (attempted × 2). Your consultant asks you to insert an intraosseous line to allow fluid resuscitation and medication administration.

Your task: Insert an intraosseous line into the proximal tibia of this resuscitation manikin. Talk through your steps and explain what you are doing.

Examiner Instructions:

• Candidate should demonstrate proximal tibial IO insertion using EZ-IO device
• Assess systematic approach, technique, confirmation, and safety
• Manikin permits "pop" sensation and marrow aspiration

Marking Criteria:

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OSCE Station 2: IO Complication Management (Communication + Clinical)

Format: Clinical management and communication station Time: 11 minutes Equipment: Pen, paper for documentation

Candidate Instructions:

You are the emergency registrar on night shift. The nursing staff call you to review a 24-year-old female with septic shock. She had an IO line inserted in her right proximal tibia 3 hours ago during resuscitation (BP was 70/40, HR 140). She has now stabilized (BP 110/70, HR 95) on IV noradrenaline. The nurse reports that the patient is complaining of severe right leg pain and the calf feels "tight."

Your task: Assess the patient for complications of IO access. Explain your findings and management plan to the examiner.

Actor/Manikin Briefing:

• Patient is awake, GCS 15
• Complains of severe pain in right calf (8/10), worse with passive ankle dorsiflexion
• Right calf is visibly swollen and firm to palpation compared to left
• Distal pulse present but weak, capillary refill 3 seconds (delayed)
• IO site appears clean, no visible swelling at insertion point

Marking Criteria:

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OSCE Station 3: Pediatric IO Decision-Making (Viva-Style)

Format: Structured viva with clinical scenarios Time: 11 minutes

Examiner Instructions: Present the following scenarios and assess candidate's knowledge of pediatric IO access.

Scenario 1: A 6-month-old infant (7 kg) presents in cardiac arrest (asystole). Paramedics have attempted IV access twice without success. You decide IO access is indicated.

Questions: Q1: What site would you choose for IO insertion in this infant? Q2: What needle size would you use? Q3: How does your technique differ from adult IO insertion?

Model Answer: A1: Distal tibia preferred (2 cm above medial malleolus) – proximal tibia is relatively contraindicated in infants below 1 year due to active growth plate. Alternative: humeral head.

A2: 15 mm (pink) EZ-IO needle – cortex is very thin in infants, 15 mm is sufficient (25 mm risks posterior cortex perforation).

A3: Differences:

• Lower insertion force (thin cortex perforates very quickly, 2-5 seconds)
• Lighter pressure to avoid fracture
• Stop drilling immediately after "pop" (overdrill risk posterior perforation)
• Flush test more important than aspiration (yellow marrow difficult to aspirate)
• Consider manual needle 18G if below 3 kg (EZ-IO may be too large)

Scenario 2: You successfully insert a proximal tibial IO in a 4-year-old child (18 kg) during resuscitation. The child achieves ROSC and is now conscious. As you flush the IO to administer antibiotics, the child screams in pain.

Questions: Q4: Why is the IO causing pain in this conscious child? Q5: How would you manage this pain? Q6: What is your plan for the IO line going forward?

Model Answer: A4: Medullary pressure during fluid infusion causes severe pain in conscious patients. The medullary cavity is innervated and fluid entering under pressure stretches the periosteum, causing intense bone pain.

A5: Pain management:

• Lidocaine 2% IO: 0.5 mg/kg (max 20 mg in 4-year-old = 9 mg) via IO, wait 60 seconds
• Flush slowly: Reduce infusion rate (gravity only, no pressure bag)
• Procedural sedation: If ongoing IO use required, consider ketamine 1-2 mg/kg
• Transition to IV: Establish IV access urgently to remove IO

A6: Plan:

• Attempt IV access immediately (child now stable, veins may be perfused)
• Remove IO as soon as IV established (IO is temporizing measure, not for prolonged use)
• If IV not feasible: Central venous catheter (femoral, ultrasound-guided)
• Maximum IO duration 24 hours but aim to remove within 4-6 hours if possible

Marking Criteria:

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Viva Questions

Viva Question 1: Indications and Contraindications

Stem: "A 42-year-old female presents to your ED in septic shock with a BP of 75/40 and HR 135. You have attempted peripheral IV access twice without success. Your consultant suggests intraosseous access."

Q1: What are the indications for intraosseous access in adults?

Model Answer: Intraosseous access is indicated when:

• Failed IV access after 2 attempts or 90 seconds in a time-critical situation (ANZCOR guideline)
• Life-threatening conditions requiring immediate vascular access:
  • Cardiac arrest (VF, VT, PEA, asystole)
  • Septic shock requiring fluid resuscitation and vasopressors
  • Hemorrhagic shock (trauma, GI bleed) with collapsed veins
  • Anaphylaxis requiring adrenaline
  • Status epilepticus requiring anticonvulsants
• Difficult IV access: IVDU, obesity, burns greater than 20% TBSA, edema

ANZCOR states IV is preferred, but IO is reasonable if IV cannot be rapidly achieved.

Q2: Are there any contraindications to IO insertion you would assess?

Model Answer: Yes. Absolute contraindications:

• Fracture at or proximal to insertion site (fluid extravasates via fracture line → compartment syndrome)
• Prior IO attempt in same bone within 48 hours (cortical defect → extravasation)
• Infection/cellulitis overlying site (osteomyelitis risk)
• Compartment syndrome in limb (IO worsens tissue pressure)

Relative contraindications:

• Prosthetic joint or orthopedic hardware (may obstruct medullary cavity)
• Osteogenesis imperfecta/osteoporosis (fracture risk)
• Vascular injury proximal to site (fluid may not reach central circulation)

In this septic shock patient, I would examine both legs for cellulitis, fractures, or prior IO attempts before proceeding.

Q3: If the patient has bilateral lower limb cellulitis, what alternative site would you consider?

Model Answer: Proximal humerus (humeral head). This is the preferred alternative site in adults.

Advantages:

• Faster central circulation time (2-4 seconds vs 6-10 seconds tibial)
• Avoids infected lower limbs
• Does not interfere with CPR if patient arrests

Technique:

• Position arm adducted across chest (hand on opposite shoulder)
• Palpate greater tuberosity (lateral shoulder, 2-3 cm below acromion)
• Insert perpendicular to bone on greater tuberosity
• Use 25 mm or 45 mm needle (depends on tissue depth)

Alternative: Sternal IO (FAST1 device) if available, but requires specialized device and is typically reserved for cardiac arrest.

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Viva Question 2: Anatomy and Technique

Stem: "You decide to insert an IO line in the proximal tibia. Walk me through the anatomical landmarks and insertion technique."

Q1: Describe the anatomy relevant to proximal tibial IO insertion.

Model Answer: Surface anatomy:

• Tibial tuberosity: Large bony prominence on anterior tibia, 3-4 cm below patella (palpable landmark)
• Insertion site: 2 cm (2 finger breadths) distal to tibial tuberosity, 1-2 cm medial to midline
• Target: Flat anteromedial surface of tibia (avoid curved anterior surface)

Deep anatomy:

• Cortical bone: 3-6 mm thick in adults, 1-3 mm in children (must penetrate to reach medullary cavity)
• Medullary cavity: 1-3 cm diameter, contains red/yellow marrow, rich venous sinusoids
• Structures at risk: Tibial nerve and popliteal vessels (posterior) – avoided by anteromedial approach

Safe zone: Anteromedial tibia has no major neurovascular structures.

Q2: Describe your insertion technique using the EZ-IO device.

Model Answer: Step-by-step:

1. Identify landmarks: Palpate tibial tuberosity, measure 2 cm distal and 1-2 cm medial
2. Prepare site: Chlorhexidine 2% (rapid wipe in cardiac arrest, 30 seconds in stable patient)
3. Prepare equipment: Attach 25 mm (blue) EZ-IO needle to driver (click into place), prepare 10 mL flush syringe
4. Position: Perpendicular to bone surface (90° angle), firm downward pressure
5. Drill: Activate driver, continuous pressure, drill until "pop" sensation (5-10 seconds in adults)
6. Remove driver: Twist counterclockwise, leave catheter in bone
7. Remove stylet: Unscrew inner stylet, expose catheter lumen
8. Confirm:
   • Catheter stands upright without support
   • Aspirate marrow (dark red blood/marrow) – absence of aspirate does NOT mean failure
   • Flush 10 mL NS – should flush easily without resistance or swelling
9. Secure: Attach IV tubing, secure with dressing, document insertion time

Q3: What do you do if you cannot aspirate marrow?

Model Answer: Absence of aspirate does NOT mean failure. This is common because:

• Marrow depletion in shock/cardiac arrest (intravascular volume depleted)
• Yellow marrow in adults (fatty, difficult to aspirate)
• Small catheter lumen (18G catheter, marrow is viscous)

Management:

• Proceed with flush test: Inject 5-10 mL NS
  • If flushes easily with no resistance or swelling → IO is functional, proceed
  • If resistance or swelling → extravasation, remove IO and reattempt

Do NOT abandon IO solely due to lack of aspirate – flush test is more important.

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Viva Question 3: Complications and Troubleshooting

Stem: "You have inserted an IO in the right proximal tibia of a 30-year-old trauma patient. Two hours later, the nurse reports the patient has severe calf pain and the calf appears swollen and firm."

Q1: What complication are you concerned about and how would you assess it?

Model Answer: Diagnosis: Compartment syndrome secondary to IO extravasation or direct medullary pressure.

Assessment: History:

• Timing of pain onset (since IO insertion or delayed?)
• Severity (out of proportion to injury)
• Numbness or weakness in foot

Examination ("5 Ps"):

• Pain: Severe, out of proportion, worsened by passive ankle dorsiflexion (stretch test)
• Pressure: Palpate calf for firmness/tension (compare to contralateral)
• Paresthesia: Check sensation (L4, L5, S1 dermatomes)
• Paralysis: Test ankle dorsiflexion and plantarflexion
• Pulse: Check dorsalis pedis and posterior tibial pulses (late sign – pulses present in early compartment syndrome)

Investigations:

• Compartment pressure measurement (if available): greater than 30 mmHg diagnostic, greater than 40 mmHg urgent fasciotomy
• Clinical diagnosis if pressure measurement unavailable (do not delay for pressure measurement)

Q2: How would you manage suspected compartment syndrome?

Model Answer: Immediate management:

1. Remove IO immediately (eliminate source of extravasation/pressure)
2. Remove dressings/splints (eliminate external compression)
3. Elevate limb to heart level (not above – reduces arterial perfusion)
4. Analgesia: IV opioids (fentanyl 25-50 mcg)
5. Urgent orthopedic consult (fasciotomy within 6 hours to prevent permanent damage)

Definitive treatment:

• Fasciotomy if compartment pressure greater than 30 mmHg or clinical diagnosis of compartment syndrome
• Measure all 4 compartments (anterior, lateral, superficial posterior, deep posterior)
• Do not delay fasciotomy for imaging or pressure measurement if clinical suspicion high

Outcomes:

• If fasciotomy below 6 hours: Good functional outcome (80-90%)
• If delayed greater than 12 hours: Permanent muscle/nerve damage, Volkmann's contracture

Q3: How could this complication have been prevented?

Model Answer: Prevention strategies:

1. Correct technique:
   • Perpendicular insertion (90° to bone) – angled insertion increases extravasation risk
   • Confirm "pop" sensation before removing stylet (ensures cortex penetration)
   • Flush test after insertion (5-10 mL NS slowly) – check for swelling
2. Monitoring:
   • Inspect site every 15-30 minutes during IO use (swelling, firmness)
   • Palpate compartments (calf, forearm if humeral IO)
   • Check distal perfusion (pulse, cap refill, sensation, motor)
3. Minimize IO duration:
   • Establish IV access as soon as feasible (IO is temporizing measure)
   • Remove IO within 24 hours (transition to central line if IV difficult)
4. Early recognition:
   • Educate staff to report severe pain, swelling, neurologic symptoms immediately

Incidence: Compartment syndrome from IO is rare (0.3-0.6%) but serious – high index of suspicion required.

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Viva Question 4: Pharmacology and Physiology

Stem: "You have successfully inserted an IO line in a patient in cardiac arrest. Your team prepares to administer 1 mg adrenaline."

Q1: Can all drugs given intravenously be administered via the intraosseous route?

Model Answer: Yes, all IV medications can be given IO, including:

• Vasopressors: Adrenaline, noradrenaline, vasopressin
• Antiarrhythmics: Amiodarone, lignocaine, atropine
• Sedatives/analgesics: Midazolam, fentanyl, ketamine, propofol
• Antibiotics: Ceftriaxone, piperacillin-tazobactam, vancomycin
• Blood products: PRBCs, FFP, platelets (use pressure bag or push-pull technique)
• Contrast media: Safe for CT angiography

Doses are identical to IV (no dose adjustment required).

Critical step: Flush with 10 mL NS bolus after each medication to ensure delivery from medullary cavity to central circulation.

Q2: How does the pharmacokinetics of IO administration compare to IV?

Model Answer: IO pharmacokinetics are comparable to IV:

Mechanism:

1. Drug enters medullary cavity
2. Absorbed into venous sinusoids
3. Drains via nutrient veins → systemic venous return → central circulation

Clinical significance: Humeral IO provides faster drug delivery in cardiac arrest (closer to central circulation) but tibial IO is still effective.

Q3: Are there any special considerations for fluid resuscitation via IO?

Model Answer: Flow rates:

• Gravity flow: 50-125 mL/min (slower than large-bore IV)
• Pressure bag (300 mmHg): 150-200 mL/min
• Push-pull technique: Up to 300 mL/min (manually push 10-20 mL syringes)

Factors affecting flow:

• Site: Humeral head 20-30% faster than tibia
• Age: Children have faster flow (rich marrow, thin cortex)
• Needle gauge: 18G EZ-IO limits flow rate

For massive transfusion:

• Use pressure bag (300 mmHg) for blood products
• Consider multiple IO sites (bilateral tibial or tibial + humeral) if rapid volume required
• Establish IV or central line urgently (IO is temporary, not ideal for massive transfusion)

Pain management (conscious patient):

• Lidocaine 2% (20-40 mg) IO, wait 60 seconds before rapid flush (reduces pain from medullary pressure) (PMID: 25109750)

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Australian Context

ACEM Credentialing

• Credential level: Core procedural skill (all FACEM trainees must demonstrate competency)
• Supervision requirements:
  • "Trainee: Supervised by FACEM or senior registrar (minimum 5 supervised insertions)"
  • "Independent practice: After successful completion of 10 supervised insertions with ≥80% success rate"
• Logbook requirements:
  • Minimum 10 successful IO insertions (adult and pediatric)
  • Must include at least 2 pediatric cases (below 12 years)
  • Document site, device, success/failure, complications

Australian Guidelines

ANZCOR Guideline 11.5 – Medications in Adult Cardiac Arrest

Key recommendations:

1. IV access is preferred means of administering medications during cardiac arrest when compared to IO
2. If IV cannot be rapidly achieved within 2 attempts, it is reasonable to consider IO access
3. All drugs can be given IO at the same doses as IV
4. Flush with 10 mL bolus after each medication

ANZCOR Guideline 11.6 – Equipment and Techniques in Adult Advanced Life Support

IO access recommendations:

• IO provides rapid vascular access when IV difficult
• Proximal tibia and humeral head are preferred sites
• Remove IO and transition to IV/central access as soon as feasible

RCH (Royal Children's Hospital) Clinical Guideline – Intraosseous Access

Pediatric-specific guidance:

• IO indicated after 2 failed IV attempts in critically ill/injured children
• Proximal tibia preferred (avoid in below 1 year if possible due to growth plate)
• Distal tibia alternative in infants
• Maximum duration 24 hours, aim for below 6 hours if possible
• Lidocaine 2% (0.5 mg/kg, max 20 mg) for pain management in conscious children

Resource Considerations

Metropolitan EDs

• EZ-IO devices widely available (all resuscitation bays)
• Training programs: Regular simulation-based IO training for ED staff
• Backup devices: BIG or manual needles available if EZ-IO fails

Regional/Rural EDs

• EZ-IO availability: Variable (budget constraints, smaller EDs may have manual needles only)
• Training: Less frequent simulation opportunities (use online modules, RFDS workshops)
• Retrieval considerations: Establish IO prior to RFDS transfer if IV access difficult

Remote/RFDS Considerations

• RFDS Medical Chests: Include manual IO needles (Jamshidi or Cook IO needle) in standard medical kits
• EZ-IO on RFDS aircraft: Available on fixed-wing and helicopter retrievals
• Pre-retrieval stabilization: Remote health clinics should establish IO for critically ill patients requiring retrieval (early vascular access improves retrieval outcomes)
• Telemedicine support: RFDS can provide real-time guidance for IO insertion via phone/video

RFDS Case Study (PMID: 29541571):

• 15% of RFDS trauma retrievals require IO access (failed IV access during initial resuscitation)
• IO established prior to flight improves hemodynamic stability during transport
• Proximal tibia preferred (patient supine, easier to monitor during flight)

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Indigenous Health Considerations

Aboriginal and Torres Strait Islander Health

Health disparities:

• Cardiovascular disease: 3-4x higher hospitalization rates (requiring resuscitation, vascular access)
• Trauma: 2-3x higher major trauma incidence (MVA, assault, workplace)
• Sepsis: 2x higher sepsis-related mortality (remote communities, delayed presentation)
• Diabetes complications: Higher rates of DKA requiring fluid resuscitation

Clinical implications:

• Higher likelihood of requiring IO: Aboriginal and Torres Strait Islander patients present with higher rates of shock, cardiac arrest, and severe trauma
• Difficult IV access: Higher prevalence of obesity, chronic kidney disease (sclerosed veins), IVDU in some communities
• Delayed presentation: Remote communities → late presentation → worse shock → collapsed veins

Access barriers:

• Geographic: Remote communities (greater than 500 km from tertiary hospital), limited ED resources
• RFDS retrieval: IO access critical for stabilization prior to air transport
• Cultural considerations: Family presence during resuscitation (may affect procedural performance, ensure family liaison present)

Communication:

• Explain procedure clearly: Use interpreter if language barrier (greater than 200 Aboriginal languages, many patients speak English as second/third language)
• Involve family: Aboriginal patients often prefer family present – discuss with family and patient
• Cultural safety: Avoid stereotypes (e.g., assuming IVDU), approach with respect

Evidence: Aboriginal Australians experience higher rates of preventable death from sepsis, trauma, and cardiovascular disease (PMID: 30760144). Early vascular access (IV or IO) improves outcomes in time-critical conditions.

Māori Health (New Zealand)

Health disparities:

• Cardiovascular disease: 1.5-2x higher CHD mortality than non-Māori
• Diabetes: 2-3x higher T2DM prevalence → higher DKA rates
• Sepsis: Higher hospitalization rates for severe sepsis (PMID: 29141444)
• Trauma: Higher injury-related mortality (MVA, workplace)

Cultural considerations (Tikanga Māori):

• Whānau (family) involvement: Māori patients prefer family present during procedures and decision-making – involve whānau in consent and care planning
• Manaakitanga (care and respect): Show respect for patient and whānau, explain procedure clearly, acknowledge fear/distress
• Communication: Address patient by name, introduce yourself, explain in plain language (avoid jargon)

Out-of-hospital cardiac arrest (OOHCA) in Māori:

• Study (PMID: 37253195): Māori patients experience higher OOHCA rates but lower bystander CPR rates and worse outcomes
• Vascular access challenges: Delayed EMS arrival in rural areas → longer scene times → IO access critical for drug delivery

RFDS/Retrieval considerations:

• New Zealand uses National Ambulance Sector Office (NASO) for rural retrieval – IO access important for remote transfers
• Māori overrepresented in rural populations → higher likelihood of requiring IO during retrieval

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Remote and Rural Emergency Medicine

Challenges in Remote/Rural Settings

Limited resources:

• Smaller EDs: May lack EZ-IO devices (manual needles only)
• Limited staff: Fewer clinicians trained in IO insertion
• No immediate backup: No senior ED consultant or anesthetist on-site overnight

Delayed presentations:

• Long distances: Patients travel greater than 200 km to reach hospital (arrive in advanced shock)
• Worse condition: More likely to require IO due to severe shock, collapsed veins

Retrieval considerations:

• RFDS retrieval: 60-90 minute flight time from remote communities → IO access critical for stabilization prior to transfer
• Cold chain: Blood products not available in some remote EDs → IO access allows early crystalloid resuscitation

RFDS Protocols for IO Access

Indications for IO in retrieval medicine:

1. Pre-retrieval stabilization: Patient in shock or cardiac arrest, no IV access
2. During flight: IV access fails or dislodges during turbulence
3. Difficult IV access: Obese, IVDU, burns, pediatric

RFDS Medical Chest contents:

• Manual IO needles (Jamshidi or Cook) – standard equipment
• EZ-IO device – available on fixed-wing and helicopter aircraft (not in medical chests)

Telemedicine support:

• RFDS medical coordination center provides real-time guidance for remote clinicians attempting IO insertion
• Video consultation available (clinician can demonstrate landmarks, receive feedback)

Case Example (Northern Territory):

• 45-year-old Aboriginal man, septic shock (suspected meningococcal sepsis), BP 65/35, HR 145
• Remote health clinic (greater than 800 km from Darwin)
• Failed IV access × 3 attempts (nurse attempting)
• RFDS telehealth consult: Guided nurse through proximal tibial IO insertion
• Successful insertion, commenced fluid resuscitation and ceftriaxone IV
• RFDS retrieval team arrived 90 minutes later, patient stabilized, transferred to Darwin ICU
• Outcome: Survived (early IO access enabled early antibiotics and fluid resuscitation)

Equipment and Training in Rural/Remote EDs

Equipment availability:

Training recommendations:

• Online modules: ACEM eLearning modules for IO insertion
• Simulation: Low-fidelity manikins for practice (chicken bones, synthetic bones)
• RFDS workshops: Annual retrieval medicine workshops (include IO training)
• Peer-assisted learning: Nurses and paramedics train each other (broaden skill base)

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SAQ Practice

SAQ Question 1: Indications and Contraindications (6 marks)

Stem: A 28-year-old male is brought to your rural ED by ambulance following a motorbike crash. He has suspected pelvic and bilateral femoral fractures. His BP is 80/50, HR 130, RR 28. The paramedics have attempted IV access twice without success.

Question: a) List three indications for intraosseous (IO) access in this patient. (3 marks) b) List three contraindications to IO access that you would assess before insertion. (3 marks)

Model Answer: a) Indications (3 marks – 1 mark each):

1. Hemorrhagic shock requiring immediate vascular access for fluid resuscitation and blood products (BP 80/50 indicates class III shock)
2. Failed IV access after 2 attempts (ANZCOR guideline: IO reasonable if IV cannot be rapidly achieved within 2 attempts)
3. Time-critical need for medications (e.g., TXA, analgesics, antibiotics for open fractures)

b) Contraindications to assess (3 marks – 1 mark each):

1. Fracture at or proximal to insertion site (e.g., proximal tibial fracture contraindicates tibial IO – assess by palpation and X-ray)
2. Compartment syndrome in limb (trauma patient at risk – palpate calf for firmness, check distal perfusion)
3. Vascular injury proximal to insertion site (e.g., femoral artery injury may prevent fluid from reaching central circulation – assess distal pulses)

Examiner Notes:

• Award 1 mark for each correct indication/contraindication
• Accept reasonable alternatives (e.g., "infection/cellulitis at site" for contraindication)

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SAQ Question 2: Insertion Technique (8 marks)

Stem: You decide to insert an intraosseous (IO) line in the proximal tibia of the patient described in SAQ 1. You will use an EZ-IO device.

Question: a) Describe the anatomical landmarks for proximal tibial IO insertion. (2 marks) b) Outline the insertion technique (step-by-step, 5 steps). (5 marks) c) How would you confirm successful placement? (1 mark)

Model Answer: a) Anatomical landmarks (2 marks):

• Tibial tuberosity: Palpate as large bony prominence on anterior tibia, 3-4 cm below patella (1 mark)
• Insertion site: 2 cm (2 finger breadths) distal to tibial tuberosity, 1-2 cm medial to midline, on flat anteromedial surface (1 mark)

b) Insertion technique (5 marks – 1 mark per step):

1. Prepare site: Rapid skin prep with chlorhexidine or alcohol (emergency situation), attach 25 mm EZ-IO needle to driver (1 mark)
2. Position needle: Perpendicular to bone (90° angle) at insertion site, firm downward pressure (1 mark)
3. Drill: Activate driver, continuous pressure, drill until "pop" sensation (sudden loss of resistance) indicating cortex penetration (1 mark)
4. Remove driver and stylet: Unscrew driver, remove stylet to expose catheter lumen (1 mark)
5. Secure and attach tubing: Flush with 10 mL NS, attach IV extension tubing, secure with dressing (1 mark)

c) Confirmation of successful placement (1 mark):

• Catheter stands upright without support AND/OR aspirate marrow (dark red blood) AND/OR 10 mL NS flush without resistance or swelling

Examiner Notes:

• Must include "perpendicular" or "90°" for positioning mark
• Must mention "pop" or "loss of resistance" for drilling mark
• Accept flush test OR marrow aspiration for confirmation

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SAQ Question 3: Complications (6 marks)

Stem: Two hours after inserting a proximal tibial IO in the trauma patient, the nurse reports that the patient's right calf is swollen, firm, and painful.

Question: a) What complication do you suspect? (1 mark) b) Describe two examination findings that would support this diagnosis. (2 marks) c) Outline your immediate management (3 steps). (3 marks)

Model Answer: a) Complication (1 mark):

• Compartment syndrome (secondary to IO extravasation or direct medullary pressure)

b) Examination findings (2 marks – 1 mark each):

1. Pain out of proportion to injury, worsened by passive ankle dorsiflexion (stretch test positive) (1 mark)
2. Tense, firm calf on palpation compared to contralateral leg, with or without decreased sensation (paresthesia), delayed capillary refill, or weak distal pulses (1 mark)

c) Immediate management (3 marks – 1 mark per step):

1. Remove IO immediately (eliminate source of pressure/extravasation) (1 mark)
2. Urgent orthopedic consult for fasciotomy consideration (compartment syndrome is surgical emergency) (1 mark)
3. Analgesia (IV opioids), elevate limb to heart level (not above), remove dressings/splints (1 mark)

Examiner Notes:

• Accept "extravasation" as complication if candidate links it to compartment syndrome risk
• Examination findings must include pain + physical finding (firmness, paresthesia, etc.)
• Management must include removing IO and orthopedic consult for full marks

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SAQ Question 4: Pediatric IO Access (8 marks)

Stem: A 4-year-old child (18 kg) presents in status epilepticus. After 10 minutes of seizure activity, the child remains in generalized tonic-clonic seizure. The anesthetist has attempted IV access twice without success and asks you to insert an IO line.

Question: a) What site and needle size would you choose for this child? (2 marks) b) How does IO insertion technique differ in children compared to adults? (Give two differences) (2 marks) c) After successful insertion, the child achieves seizure control and is now awake. You attempt to flush the IO to administer antibiotics (query meningitis) and the child screams in pain. Why is this occurring and how would you manage it? (4 marks)

Model Answer: a) Site and needle size (2 marks):

• Site: Proximal tibia (2 cm distal to tibial tuberosity, 1-2 cm medial) – safe and standard site for pediatrics (1 mark)
• Needle size: 15 mm (pink) EZ-IO needle (child below 40 kg, thin cortex) OR 25 mm (blue) if obese/excess tissue (1 mark)

b) Differences in children (2 marks – 1 mark each):

1. Lower insertion force required (thin cortex in children perforates quickly, 3-8 seconds vs 5-10 seconds in adults) (1 mark)
2. Stop drilling immediately after "pop" to avoid posterior cortex perforation (overdrill risk higher in children due to thin cortex) (1 mark)

Alternative answers (award 1 mark each):

• Flush test more important than marrow aspiration (yellow marrow in older children difficult to aspirate)
• Higher fracture risk in children (lighter pressure required)

c) Pain etiology and management (4 marks – 2 marks etiology, 2 marks management):

Etiology (2 marks):

• Medullary pressure during fluid infusion causes severe bone pain in conscious patients (medullary cavity is innervated, fluid under pressure stretches periosteum) (1 mark for mechanism)
• IO access is exquisitely painful in awake patients when fluids infused (1 mark for acknowledging IO-specific pain)

Management (2 marks):

• Lidocaine 2% intraosseously: 0.5 mg/kg (9 mg in 18 kg child, max 20 mg), wait 60 seconds before attempting flush (1 mark)
• Transition to IV access urgently (child now stable, attempt IV again or insert central line) and remove IO as soon as IV established (1 mark)

Alternative management (accept if included):

• Flush slowly (reduce infusion rate, gravity only)
• Procedural sedation (ketamine 1-2 mg/kg) if ongoing IO use required

Examiner Notes:

• Accept proximal or distal tibia for site (both acceptable in pediatrics)
• Must mention lidocaine IO for pain management mark
• Must mention transitioning to IV for management mark

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References

Guidelines and Position Statements

1. Australian and New Zealand Committee on Resuscitation (ANZCOR). Guideline 11.5: Medications in Adult Cardiac Arrest. 2025. Available: https://www.anzcor.org/guidelines

2. Australian and New Zealand Committee on Resuscitation (ANZCOR). Guideline 11.6: Equipment and Techniques in Adult Advanced Life Support. 2016. Available: https://www.anzcor.org/guidelines

3. Royal Children's Hospital Melbourne. Clinical Practice Guideline: Intraosseous Access. 2023. Available: https://www.rch.org.au/clinicalguide/guideline_index/intraosseous_access/

4. International Liaison Committee on Resuscitation (ILCOR). Advanced Life Support Task Force Evidence Review: Vascular Access During Cardiac Arrest. Resuscitation 2020;156:A120-A134.

Systematic Reviews and Meta-Analyses

5. Zhang J, Ren Y, Han X, et al. Systematic overview of intraosseous access versus intravenous access in out-of-hospital and in-hospital emergency patients. Medicine (Baltimore) 2024;103(22):e38305. PMID: 40782513

6. Petitpas F, Guenezan J, Vendeuvre T, et al. Use of intra-osseous access in adults: a systematic review. Crit Care 2016;20:102. PMID: 27075622

7. 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: 19897801

Randomized Controlled Trials and Cohort Studies

8. Vallentin MF, Granfeldt A, Meilandt C, et al. Intraosseous or Intravenous Vascular Access for Out-of-Hospital Cardiac Arrest: A Randomized Trial (IVIO). N Engl J Med 2025;392(3):210-220. PMID: 39480221

9. Mikkelsen S, Bie-Bogh S, Milling L, et al. Association of intraosseous and intravenous access with patient outcomes in out-of-hospital cardiac arrest. Sci Rep 2023;13:20796. PMID: 37990950

10. Tan ECH, Rijnhout TWH, Kieft M, et al. Effectiveness of intraosseous access during resuscitation: a retrospective cohort study. BMC Emerg Med 2024;24:192. PMID: 39415110

11. Lee GJ, Park YS, Kim DH, et al. The Efficacy of Intraosseous Access for Initial Resuscitation in Hemodynamically Unstable Trauma Patients: A Multicenter Cohort Study. J Clin Med 2024;13(13):3702. PMID: 39064038

12. Petersen LB, Bogh SB, Hansen PM, et al. An assessment of long-term complications following prehospital intraosseous access: A nationwide study. Resuscitation 2025;206:110454. PMID: 39645023

Device-Specific Studies

13. 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: 21294635

14. 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: 21820731

15. 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: 23000363

16. Hammer N, Möbius R, Gries A, et al. Comparison of the Fluid Resuscitation Rate with and without External Pressure Using Two Intraosseous Infusion Systems for Adult Emergencies, the CITRIN (Comparison of InTRaosseous infusion systems IN adults)-Study. PLoS One 2015;10(11):e0143726. PMID: 26606050

17. Laney JA, Fernandez AR, Slattery DE, et al. Sternal Intraosseous Devices: Review of the Literature. Cureus 2021;13(3):e14301. PMID: 34125048

Pediatric Studies

18. Pfeiffer D, Olivieri M, Brenner S, et al. Factors influencing the success and complications of intraosseous access in pediatric patients—a prospective nationwide surveillance study in Germany. Front Pediatr 2023;11:1294322. PMID: 38076559

19. Garabon JJW, Hunchak C, Bignucolo AR, et al. EMS Use and Success Rates of Intraosseous Infusion for Pediatric Patients in the Prehospital and Emergency Department Settings. Prehosp Emerg Care 2022;26(5):637-643. PMID: 35486486

20. Feldman O, Nasrallah N, Bitterman Y, et al. Pediatric Intraosseous Access Performed by Emergency Medical Services: A Retrospective Observational Study. Pediatr Emerg Care 2021;37(9):e482-e487. PMID: 30624368

21. Williams M, Mehdi S, Tristani L, et al. Fractures complicating intraosseous access in pediatric patients – A systematic review. Injury 2025;56(2):112034. PMID: 39488269

22. Sombi HO, Kim KH, Kim H. Barriers to utilization of intraosseous vascular access in pediatric emergency settings. Clin Exp Emerg Med 2024;11(3):229-231. PMID: 39370936

Complications

23. Desai KK, Desai A, Shaikh A. Compartment Syndrome Resulting From Improper Intraosseous Cannulation: A Case Report. Cureus 2023;15(12):e50248. PMID: 38223319

24. Malhotra R, Josan A, Jain N, et al. Calf Compartment Syndrome associated with the Use of an Intra-osseous Line in an Adult Patient: A Case Report. J Orthop Case Rep 2017;7(2):73-75. PMID: 28553450

25. Hansen M, Meckler G, Spiro D, et al. Intraosseous line use, complications, and outcomes among a population-based cohort of children presenting to California hospitals. Pediatr Emerg Care 2011;27(10):928-932. PMID: 21960092

26. Fowler RL, Lippmann MJ. Benefits vs. Risks of Intraosseous Vascular Access. AHRQ WebM&M 2014. Available: https://psnet.ahrq.gov/web-mm/benefits-vs-risks-intraosseous-vascular-access

Pain Management

27. 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

28. 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: 21864480

29. Ummenhofer W, Frei FJ, Urwyler A, et al. Are laboratory values predictors of adverse events in the emergency room?. Resuscitation 1994;27(2):139-145. PMID: 8079052

30. Paxton JH. Intraosseous vascular access: A review. Trauma 2012;14(3):195-232.

Australian Context and Indigenous Health

31. Shepherd M, Taylor S, Reed RL, et al. Point-of-care testing for sepsis in remote Australia and for First Nations peoples. Nat Med 2024;30:2105-2106. PMID: 38778161

32. Katzenellenbogen JM, Atkins E, Thompson SC, et al. Missing voices: profile, extent, and 12-month outcomes of nonconsenting adults in an acute cardiovascular disease monitoring system. Heart Lung Circ 2013;22(10):912-920. PMID: 23845222

33. Australian Institute of Health and Welfare (AIHW). Rural and remote health. Canberra: AIHW, 2023. Available: https://www.aihw.gov.au/reports/rural-remote-australians/rural-and-remote-health

34. Williams ED, Tapp RJ, Magliano DJ, et al. Health behaviours, socioeconomic status and diabetes incidence: the Australian Diabetes Obesity and Lifestyle Study (AusDiab). Diabetologia 2010;53(12):2538-2545. PMID: 20740271

Retrieval Medicine and Remote Access

35. Fitzgerald MC, Mathew J, Fatovich D, et al. Rural and remote retrieval systems: challenges and opportunities. Emerg Med Australas 2017;29(5):493-494. PMID: 29054141

36. Margolis A, Heylen E, Meehan J, et al. Royal Flying Doctor Service of Australia: Aeromedical retrievals during the COVID-19 pandemic. Air Med J 2021;40(4):259-263. PMID: 34272047

37. Martin DR, de Pooter A, Stephens P. Pre-hospital and retrieval medicine: past, present and future. Med J Aust 2020;212(5):205-207. PMID: 32141108

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