Intraosseous Access

Quick Answer

Intraosseous (IO) access provides rapid, reliable vascular access when peripheral IV cannulation fails or is unlikely to succeed within 90 seconds. It is the recommended second-line vascular access route in cardiac arrest and shock. The procedure involves inserting a specialized needle into the bone marrow cavity—most commonly the proximal tibia (2 cm below tibial tuberosity, medial aspect) or proximal humerus (greater tubercle) in adults. Success rates exceed 90% with insertion times less than 90 seconds. All IV medications, fluids, and blood products can be administered via the IO route with equivalent pharmacokinetics. Complications are rare (0.6-1.5%) but include compartment syndrome (extravasation), osteomyelitis (under 0.5% if >24 hours), and fracture. IO access should be removed within 24-48 hours once alternative IV access is secured.

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CICM Exam Focus

High-Yield Topics:

• Indications: Failed IV access in arrest/shock, time-critical emergencies
• Anatomical sites: Proximal tibia (pediatrics/adults), humeral head (adults), distal tibia
• Insertion technique: Perpendicular approach, loss of resistance, marrow aspiration
• Contraindications: Fracture, infection, previous IO same bone under 48h, compartment syndrome
• Pharmacology: All IV drugs/fluids equivalent, onset/levels comparable to CVC
• Flow rates: Gravity 40-50 mL/h, pressure bag 125-250 mL/h, rapid infuser 1-5 L/h
• Complications: Compartment syndrome (0.6%), extravasation, osteomyelitis (under 0.5%), fracture, fat embolism
• Confirmation: Aspiration of marrow, infusion without resistance, needle stability
• Pain management: Lidocaine 40 mg slow IO push for conscious patients
• Removal technique: Unscrew with rotation, sterile dressing, monitor for bleeding

SAQ Patterns:

• Indications and contraindications for IO access
• Anatomical landmarks and insertion technique (proximal tibia vs humerus)
• Pharmacology and flow rates via IO route
• Complications and their management
• Paediatric vs adult IO access differences

Viva Scenarios:

• Failed IV access in cardiac arrest - IO insertion decision-making
• Extravasation and compartment syndrome recognition
• Conscious patient requiring IO - pain management
• Paediatric IO access in anaphylaxis
• Remote/rural retrieval requiring prolonged IO use

Hot Case Presentations:

• Post-arrest patient with IO line - when to remove, complications to monitor
• Trauma patient with IO access - assessment of adequacy, transition to CVC
• Shock patient requiring rapid fluid resuscitation via IO

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Key Points

Note: ARC Guideline 11.5: Intraosseous access is the recommended alternative when peripheral IV access cannot be achieved rapidly (within 90-120 seconds or after 2 attempts) in the cardiac arrest or critically unwell patient. It should NOT delay resuscitation.

Critical Alert: Red Flag: Compartment syndrome can develop from extravasation if the IO needle is malpositioned (not in marrow cavity) or dislodges. Monitor for pain (out of proportion), swelling, firmness, and neurovascular compromise. Requires immediate needle removal and surgical consultation.

⚠️ Warning: Pain Alert: IO infusion in conscious or sedated patients causes severe pain from intramedullary pressure. Administer 2% preservative-free lidocaine 40 mg (20-40 mg adults, 0.5 mg/kg pediatrics) slowly via IO route, wait 60 seconds, then flush with 5-10 mL saline before commencing fluid resuscitation.

• IO access is pharmacokinetically equivalent to IV - same onset times, peak levels for all resuscitation drugs
• Proximal tibia preferred in pediatrics - 2 cm below tibial tuberosity, medial flat aspect
• Humeral head preferred in adults - greater tubercle, higher flow rates than tibia (150 vs 90 mL/min with pressure)
• Success rate 85-95% first attempt, insertion time less than 90 seconds
• Remove within 24 hours ideally, maximum 48-72 hours (osteomyelitis risk under 0.5% if >24 hours)
• Contraindicated in fractured bone, infection at site, previous IO same bone under 48 hours, compartment syndrome
• Confirm placement by aspirating marrow (not always successful), infusion without resistance, needle stability
• All IV drugs/fluids permissible - crystalloids, colloids, blood products, vasopressors, antibiotics, anesthetics

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Indications

Absolute Indications

Relative Indications

• Difficult IV access (obesity, IV drug use, chronic illness, edema) when rapid access required
• Hostile environment (prehospital, retrieval, combat) where IV attempts may be limited
• Multiple failed IV attempts in non-emergency setting (replace with CVC if time permits)
• Bridge to central access in unstable patient (IO for immediate resuscitation, CVC once stabilized)
• Mass casualty situations (IO faster and more successful than IV in untrained providers)

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Contraindications

Absolute Contraindications

Relative Contraindications

• Prosthetic joint or hardware at insertion site (use alternate site)
• Recent orthopedic surgery same bone (use alternate site)
• Severe coagulopathy (increased bleeding risk - apply pressure post-removal)
• Overlying burn or tissue injury (increased infection risk - use clean site)

Not Contraindications

Note: - Age - IO access safe from neonates to elderly (adjust needle length)

• Weight - No upper weight limit (ensure adequate needle length)
• Sternotomy - Does not preclude humeral IO access
• Bilateral lower limb fractures - Use humeral head

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Anatomical Sites

1. Proximal Tibia (Preferred Pediatrics, Suitable Adults)

Landmarks:

• Location: 2 cm (1-2 fingerbreadths) below and medial to the tibial tuberosity
• Surface anatomy: Palpate tibial tuberosity; move 2 cm distally; find flat medial surface
• Depth: 10-15 mm in children, 20-30 mm in adults

Advantages:

• Large, easily palpable landmark
• Thick cortex provides secure needle placement
• Accessible in supine or sitting patient
• Familiar site for most clinicians
• Safe distance from growth plate in children (>2 cm distal to physis)

Disadvantages:

• Lower flow rates than humerus (90 mL/min vs 150 mL/min with pressure)
• Longer circulation time to central vessels (40-60 seconds vs 20-30 seconds humerus)
• Difficult in kneeling or prone CPR position
• Painful on insertion in conscious patients

Contraindications:

• Tibial plateau or shaft fracture
• Anterior compartment syndrome
• Tibial surgery or hardware
• Previous IO same leg under 48 hours

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2. Proximal Humerus (Preferred Adults)

Landmarks:

• Location: Greater tubercle of the humerus
• Patient position: Arm adducted, hand on abdomen (internally rotate shoulder to expose greater tubercle)
• Surface anatomy: Palpate acromion process; move 1-2 cm below; identify greater tubercle prominence
• Insertion: Perpendicular or 45° angle toward shoulder, 20-30 mm depth

Advantages:

• Highest flow rates of all IO sites (150-250 mL/min with pressure)
• Fastest drug delivery to central circulation (20-30 seconds vs 40-60 seconds tibia)
• Accessible during chest compressions
• Suitable for bilateral placement if needed
• Less painful than tibia in conscious patients

Disadvantages:

• Requires arm adduction (may interfere with CPR hand positioning)
• More difficult landmark identification in obese patients
• Proximity to neurovascular structures (axillary nerve, artery)
• Higher risk of dislodgement with patient movement

Contraindications:

• Humeral fracture
• Shoulder dislocation or injury
• Humeral surgery or hardware
• Previous IO same arm under 48 hours

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3. Distal Tibia (Pediatrics/Adults)

Landmarks:

• Location: 2 cm proximal to medial malleolus
• Surface anatomy: Palpate medial malleolus; move 2 cm proximal; identify flat anteromedial surface
• Insertion: Perpendicular to bone, angled slightly cephalad (away from ankle joint)
• Depth: 10-15 mm children, 15-25 mm adults

Advantages:

• Accessible when proximal tibia unavailable
• Easy landmark in all ages
• Suitable for conscious patients (less painful than proximal tibia)

Disadvantages:

• Lower flow rates than proximal tibia
• Proximity to ankle joint (avoid angulation toward joint)
• Risk of growth plate injury in young children (under 6 years)
• Thin cortex in elderly (higher fracture risk)

Contraindications:

• Ankle fracture or dislocation
• Tibial fracture
• Previous IO same leg under 48 hours

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4. Alternate Sites (Rarely Used)

• Distal femur (medial epicondyle) - difficult landmark, rarely used
• Anterior superior iliac spine - difficult in obese, rarely used
• Sternum (historical, no longer recommended) - risk of mediastinal injury, cardiac tamponade

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Equipment

Commercial IO Devices

EZ-IO Needle Selection (Most Common Device):

Rule of Thumb: If you cannot palpate bone easily through overlying tissue, use the longer needle.

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Essential Equipment Checklist

• IO device (EZ-IO with appropriately sized needle most common)
• Antiseptic (2% chlorhexidine in 70% alcohol preferred, or povidone-iodine)
• Sterile gloves (non-sterile acceptable in true emergency)
• 10 mL syringe for aspiration
• Flush syringe with 10 mL 0.9% saline (pre-filled preferred)
• Lidocaine 2% preservative-free 20-40 mg for conscious patients
• IV extension set and 3-way tap
• Pressure bag or rapid infuser (if rapid fluid resuscitation required)
• Secure dressing (transparent dressing + gauze padding)
• Sharps container for stylet disposal

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Insertion Technique

Pre-Procedure Steps

1. Identify indication - Failed IV access or anticipated difficult IV in time-critical emergency
2. Select site - Proximal tibia (pediatrics), humeral head (adults in arrest), distal tibia (alternate)
3. Position patient - Supine for tibia, arm adducted with hand on abdomen for humerus
4. Identify landmarks - Palpate bony landmarks carefully
5. Check contraindications - No fracture, infection, or previous IO under 48h at selected site
6. Prepare equipment - Attach appropriately sized needle to EZ-IO drill, prepare syringes
7. Antisepsis - 2% chlorhexidine (or povidone-iodine if chlorhexidine unavailable), allow to dry if time permits

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Insertion Technique (EZ-IO Drill - Most Common)

Step-by-Step:

1. Stabilize limb - Assistant holds limb firmly, or place rolled towel behind knee (tibia) or under shoulder (humerus)

2. Identify insertion point - Mark with finger or pen:

   • Proximal tibia: 2 cm below tibial tuberosity, medial flat surface
   • Humeral head: Greater tubercle, 1-2 cm below acromion
   • Distal tibia: 2 cm above medial malleolus, anteromedial surface

3. Apply antiseptic - 2% chlorhexidine, allow to dry 30 seconds (if time permits)

4. Attach needle to drill - Ensure needle securely locked into drill chuck, remove rubber cap from needle

5. Position needle perpendicular to bone surface (90° angle)

   • Tibia: Perpendicular or slightly caudad (away from growth plate)
   • Humerus: 45° medial angulation toward glenoid fossa
   • Distal tibia: Perpendicular or slightly cephalad (away from ankle joint)

6. Apply firm downward pressure while activating drill - Press firmly to penetrate cortex, do NOT rely on drill alone

7. Drill until loss of resistance (sudden "give") - Usually 10-30 mm depth

   • Resistance → cortex not breached, continue drilling with pressure
   • Sudden loss of resistance → entered marrow cavity, STOP immediately
   • Feel "pop" or loss of resistance - this is the cortical breach

8. Remove drill, leave needle in place - Needle should stand upright without support

9. Remove stylet (central obturator) - Dispose in sharps container immediately

10. Aspirate marrow (confirmation) - Attach 10 mL syringe, aspirate gently:

    • Success: Dark blood with marrow particles (confirms marrow cavity)
    • Failure to aspirate (15-20% cases): Does NOT indicate malposition - proceed to flush test
    • Send aspirate for labs if needed (blood gas, glucose, lactate)

11. Flush test - Attach pre-filled 10 mL saline syringe:

    • Flush 5-10 mL saline briskly
    • Success: No resistance, no swelling at site (confirms marrow cavity)
    • Failure: High resistance or swelling at site (extravasation → remove and reattempt)

12. Secure needle - Attach extension set, secure with dressing:

    • Apply transparent dressing over insertion site
    • Pad around needle hub with gauze to prevent movement
    • Tape extension set to limb to prevent dislodgement

13. Confirm stability - Needle should not move with gentle manipulation

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Pain Management (Conscious Patients)

⚠️ Warning: Intraosseous infusion causes severe pain in conscious or lightly sedated patients due to increased intramedullary pressure. Pain management is ESSENTIAL before commencing fluid resuscitation.

Lidocaine Protocol:

1. Draw up lidocaine - 2% preservative-free lidocaine:

   • Adults: 40 mg (2 mL of 2% solution)
   • Children: 0.5 mg/kg (0.25 mL/kg of 2% solution, maximum 40 mg)

2. Administer slowly - Push lidocaine via IO over 60-120 seconds (NOT bolus)

3. Wait 60 seconds - Allow lidocaine to diffuse through marrow

4. Flush - 5-10 mL 0.9% saline to distribute lidocaine

5. Commence infusion - Start medications/fluids (pain should be minimal)

Alternative: Pre-emptive IV sedation/analgesia if IO likely to be required (e.g., fentanyl 1-2 mcg/kg IV, ketamine 0.25-0.5 mg/kg IV)

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Manual Jamshidi Needle Technique (If Powered Device Unavailable)

1. Position needle perpendicular to bone
2. Apply firm downward pressure while rotating clockwise with palm of hand
3. Use twisting, boring motion with steady pressure
4. Continue until sudden loss of resistance (cortical breach)
5. Remove stylet, aspirate, flush as above
6. Note: Requires significantly more force and time (60-90 seconds vs 10 seconds for drill)

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Pharmacology and Fluid Administration

Drug Pharmacokinetics (IO vs IV)

Note: Critical Principle: The intraosseous route is pharmacokinetically equivalent to the intravenous route for ALL resuscitation medications. Time to peak plasma concentration and peak levels are comparable.

Key Points:

• Humeral IO is 15-30 seconds faster than tibial IO (proximity to central circulation)
• Same doses as IV route for all medications (no dose adjustment required)
• Bioavailability is 90-100% for all drugs tested
• Onset times slightly delayed vs IV (10-30 seconds) but clinically insignificant in arrest

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Medications and Fluids Permissible via IO Route

ALL intravenous medications and fluids can be given via IO route, including:

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Flow Rates and Infusion Techniques

Maximizing Flow Rates:

1. Use largest needle - 15G provides higher flow than 18G
2. Use proximal humerus if possible - 50-100 mL/min faster than tibia
3. Apply pressure bag at 300 mmHg - increases flow 3-5× over gravity
4. Use rapid infuser for trauma/massive transfusion - can achieve 3-5 L/h
5. Warm fluids - Cold fluids increase viscosity and reduce flow
6. Use bilateral IO if single site inadequate (e.g., massive hemorrhage requiring >5 L/h)

Pediatric Fluid Bolus Technique:

• Use 60 mL syringe to manually push fluid
• Withdraw 60 mL from fluid bag, push via 3-way tap over 2-3 minutes
• Repeat as needed to achieve 20 mL/kg bolus
• Faster than pressure bag in small children (veins collapse with high pressure)

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Complications and Troubleshooting

Complications (Incidence and Management)

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Troubleshooting Failed Insertion

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Confirmation of Correct Placement

Primary Confirmation Methods

1. Aspiration of marrow (Gold Standard, but only successful 70-85% of time)

   • Dark blood with particulate matter (marrow spicules)
   • Can send for blood gas, glucose, lactate (correlate well with venous samples)
   • Absence of marrow does NOT indicate failure (dry marrow in elderly, chronic illness)

2. Flush test (Most reliable if aspiration unsuccessful)

   • Attach 10 mL pre-filled saline syringe
   • Flush 5-10 mL briskly
   • Success: No resistance, no swelling → needle in marrow cavity
   • Failure: High resistance or swelling → extravasation, remove immediately

3. Needle stability

   • Needle stands upright without support (not leaning or falling)
   • No movement with gentle manipulation

4. Infusion test

   • Connect IV tubing, open roller clamp
   • Fluid flows freely under gravity (if tibia) or pressure (if humerus)
   • No swelling at insertion site or distal to insertion

Secondary Confirmation (Not Routine)

• X-ray or ultrasound - Needle visible in marrow cavity (only if clinical doubt)
• Blood gas from aspirate - pH, PO2, PCO2 correlate with venous values (not arterial)
• Dye injection under fluoroscopy - Research only, not practical clinically

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Removal Technique

Indications for IO Removal

1. Alternative IV access secured (peripheral IV or CVC)
2. 24-48 hours elapsed (osteomyelitis risk increases)
3. Complication suspected (extravasation, compartment syndrome, infection)
4. Patient discharge from ICU (should not leave ICU with IO in situ)
5. Death (medicolegal requirement to remove all invasive devices)

Removal Procedure

1. Prepare equipment - Sterile gauze, antiseptic, adhesive dressing, gloves

2. Explain to patient (if conscious) - Brief discomfort during removal

3. Stabilize limb - Hold limb steady, support at joint

4. Unscrew needle - Grasp hub firmly, rotate counter-clockwise while applying gentle traction

   • EZ-IO needles: Use counter-clockwise rotation (threads engage during insertion)
   • Manual needles: Pull straight out with firm, steady traction

5. Apply pressure - Immediate pressure over insertion site with sterile gauze for 5 minutes

   • If coagulopathic (e.g., post-massive transfusion): Apply pressure for 10-15 minutes

6. Apply dressing - Adhesive bandage or transparent dressing once hemostasis achieved

7. Monitor site - Check for bleeding, hematoma, signs of infection at 24 hours

8. Document - Record insertion time, removal time, total dwell time, site appearance

9. Dispose of needle - Place in sharps container (do NOT re-cap stylet)

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Special Populations

Pediatric IO Access

Key Differences:

• Preferred site: Proximal tibia (2 cm below tibial tuberosity, medial aspect) at all ages
• Alternate site: Distal tibia (>6 years), humeral head (>40 kg)
• Needle selection: 15 mm (pink) for under 40 kg, 25 mm (blue) for >40 kg
• Lidocaine dose: 0.5 mg/kg IO (maximum 40 mg) for conscious children
• Fluid bolus technique: 60 mL syringe push (20 mL/kg over 5-10 min) faster than pressure bag

Indications:

• Cardiac arrest (after 2 IV attempts or 90 seconds)
• Septic shock requiring immediate fluid resuscitation
• Anaphylaxis without IV access
• Status epilepticus requiring immediate benzodiazepines
• Severe dehydration (gastroenteritis) unresponsive to oral rehydration

Complications:

• Growth plate injury (under 0.1%) - avoid insertion through physis, use ≥2 cm distal to growth plate
• Psychological trauma - minimize attempts, provide procedural sedation if time permits

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Elderly and Osteoporotic Patients

Challenges:

• Brittle bones - Higher fracture risk (0.5% vs 0.1% in younger adults)
• Thickened cortex - May require more force/time to penetrate
• Dry marrow - Aspiration often unsuccessful (70% vs 85% in younger patients)
• Multiple comorbidities - Coagulopathy, immunosuppression increase complication risk

Modifications:

• Use powered drill (EZ-IO) rather than manual to reduce force and fracture risk
• Confirm with flush test (aspiration less reliable)
• Apply pressure longer post-removal (5-10 minutes) if on anticoagulants
• Monitor closely for infection (immunocompromised, diabetes)

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Obese Patients

Challenges:

• Difficult landmark identification - Thick adipose tissue obscures bony landmarks
• Inadequate needle length - Standard 25 mm needle may not reach marrow

Solutions:

• Palpate landmarks carefully - May need firmer palpation to feel bone
• Use 45 mm (yellow) needle if tissue depth >25 mm
• Consider humeral head - Easier landmark than tibia in morbid obesity
• Ultrasound guidance - Can identify bone depth and guide needle insertion (rarely needed)

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Burns Patients

Indications:

• Extensive burns limiting IV sites
• Shock requiring immediate resuscitation
• Burn area includes all limbs

Site Selection:

• Choose unburned site - Avoid insertion through burned tissue (infection risk)
• Proximal humerus often spared in limb burns
• Proximal tibia if lower limbs unburned

Fluid Resuscitation:

• IO suitable for Parkland formula fluid delivery (use rapid infuser or pressure bag)
• Remove IO within 24 hours once CVC secured (lower infection risk)

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Remote and Rural Settings

Challenges:

• Limited equipment - May only have manual Jamshidi needles
• Prolonged dwell time - Transfer to tertiary center may take hours (RFDS retrieval)
• Limited sterile supplies - Austere environment

Australian Context:

• RFDS protocols recommend IO access for:
  • Cardiac arrest in remote community
  • Shock requiring resuscitation during retrieval
  • Pediatric emergencies when IV attempts fail
• Dwell time up to 48 hours acceptable during retrieval if no complications
• Telehealth support - RFDS medical consultation can guide insertion remotely

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Indigenous Health Considerations

Aboriginal and Torres Strait Islander Patients

Epidemiology:

• Higher rates of conditions requiring emergency vascular access:
  • Sepsis (2-3× higher incidence)
  • Diabetic emergencies (DKA, HHS) (3× higher)
  • Renal failure (10× higher ESKD rate)
  • Cardiac arrest (1.5-2× higher out-of-hospital CA)

Cultural Considerations:

• Family involvement - Include family members in decision-making if possible (not always feasible in cardiac arrest)
• Aboriginal Health Worker (AHW) presence - AHW can provide cultural support and explain procedure
• Language barriers - Use interpreter if patient/family has limited English (Aboriginal interpreter services)
• Trust and consent - Historical medical mistrust; explain procedure clearly, obtain verbal consent if conscious

Clinical Considerations:

• Chronic kidney disease - Higher rates of renal bone disease (osteodystrophy) may increase fracture risk
• Diabetes complications - Higher infection risk (osteomyelitis); remove IO promptly
• Remote location - IO may be only option for hours until retrieval (RFDS) - acceptable dwell time up to 48 hours
• Limited resources - Remote clinics may only have manual Jamshidi needles (not powered drills)

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Māori Patients (New Zealand)

Cultural Considerations:

• Whānau (family) involvement - Include whānau in decision-making process
• Tapu (sacredness) of body - Explain procedure respectfully, minimize unnecessary interventions
• Māori Health Worker presence - Can provide cultural support and translation (te reo Māori)
• Tikanga (customs) - Respect cultural protocols, involve kaumātua (elders) if available

Clinical Considerations:

• Higher rates of rheumatic fever - May have cardiac complications requiring resuscitation
• Socioeconomic disparities - Delayed presentation may mean more severe illness requiring IO
• Rural location - Similar to Australian remote settings, prolonged IO dwell time may be necessary

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SAQ Practice Questions

SAQ 1: Indications, Technique, and Complications

Question (20 marks):

A 65-year-old man presents to the emergency department in cardiac arrest. After 2 minutes of CPR, the paramedic has been unable to secure IV access despite multiple attempts.

(a) List FOUR absolute indications for intraosseous (IO) access. (4 marks)

(b) Describe the anatomical landmarks and insertion technique for proximal tibial IO access in an adult. (6 marks)

(c) List FOUR contraindications to IO access at a specific site. (4 marks)

(d) Describe the management of compartment syndrome following IO insertion. (6 marks)

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Model Answer:

(a) Absolute indications for IO access (4 marks):

1. Cardiac arrest with failed peripheral IV access (≥2 attempts or >90 seconds) - IO provides rapid reliable access when IV impossible [1 mark]

2. Shocked patient (septic, hypovolemic, anaphylactic) with failed peripheral IV access - vasoconstriction makes IV difficult, IO unaffected by perfusion [1 mark]

3. Pediatric emergency unable to secure IV rapidly (after 2 attempts or 90 seconds) - small mobile veins, IO success rate >90% [1 mark]

4. Major trauma with hypovolemia and difficult IV access - anatomical disruption and vasoconstriction impair IV, IO provides immediate access [1 mark]

Alternative acceptable answers: Anaphylaxis with difficult IV access, burns with limited IV sites

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(b) Anatomical landmarks and insertion technique for proximal tibial IO access (6 marks):

Landmarks (2 marks):

• Location: 2 cm (1-2 fingerbreadths) below and medial to the tibial tuberosity [1 mark]
• Surface anatomy: Palpate tibial tuberosity; move 2 cm distally; identify flat medial surface [0.5 mark]
• Depth: Approximately 20-30 mm in adults [0.5 mark]

Insertion technique (4 marks):

1. Stabilize limb - Place rolled towel behind knee, ensure leg stable [0.5 mark]

2. Antisepsis - Apply 2% chlorhexidine, allow to dry if time permits [0.5 mark]

3. Position needle perpendicular to bone surface (90° angle), slightly caudad away from growth plate [0.5 mark]

4. Apply firm pressure while drilling - Press down while activating powered drill (EZ-IO), drill until sudden loss of resistance ("give" or "pop" indicates cortical breach) [1 mark]

5. Remove drill and stylet - Needle should stand upright without support [0.5 mark]

6. Confirm placement - Aspirate marrow (dark blood with particles) OR flush 5-10 mL saline (no resistance, no swelling confirms marrow cavity) [0.5 mark]

7. Secure - Attach extension set, apply transparent dressing, pad hub with gauze to prevent movement [0.5 mark]

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(c) Contraindications to IO access at a specific site (4 marks):

1. Fracture at insertion site - Risk of extravasation through fracture line, impaired marrow cavity [1 mark]

2. Previous IO attempt same bone under 48 hours - Risk of extravasation through prior puncture site [1 mark]

3. Cellulitis or skin infection at insertion site - Risk of osteomyelitis from introducing bacteria into bone [1 mark]

4. Compartment syndrome in that limb - Extravasation will worsen compartment pressure, circulation already compromised [1 mark]

Alternative acceptable answers: Bone disease (osteogenesis imperfecta, osteopetrosis), prosthetic joint at site, recent orthopedic surgery same bone, overlying burn

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(d) Management of compartment syndrome following IO insertion (6 marks):

Recognition (2 marks):

• Pain out of proportion to injury (earliest and most sensitive sign) [0.5 mark]
• Swelling, firmness, tense compartment on palpation [0.5 mark]
• Late signs: Pallor, pulselessness, paresthesia, paralysis (indicate irreversible damage) [0.5 mark]
• Measure compartment pressure if available (>30 mmHg diagnostic) [0.5 mark]

Immediate Management (2 marks):

• Remove IO immediately - Stop all infusions [0.5 mark]
• Elevate limb to heart level (NOT above heart - reduces arterial inflow) [0.5 mark]
• Analgesia - Opioid analgesia (morphine 2.5-5 mg IV or fentanyl 25-50 mcg IV) [0.5 mark]
• Monitor neurovascular status - Pulses, capillary refill, sensation, motor function every 15 minutes [0.5 mark]

Definitive Management (2 marks):

• Urgent surgical consultation (orthopedics or general surgery) [0.5 mark]
• Emergency fasciotomy if compartment pressure >30 mmHg or clinical diagnosis confirmed (within 6 hours to prevent permanent damage) [1 mark]
• Avoid ice (causes vasoconstriction and worsens ischemia) [0.5 mark]

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SAQ 2: Pharmacology and Flow Rates

Question (20 marks):

A 4-year-old child (20 kg) presents to the emergency department in septic shock with a capillary refill time of 5 seconds, heart rate 180 bpm, and blood pressure 70/40 mmHg. Two attempts at peripheral IV cannulation have failed.

(a) Justify the use of intraosseous (IO) access in this child. (4 marks)

(b) Compare the pharmacokinetics of medications administered via the IO route versus the IV route. (6 marks)

(c) Describe how you would deliver a 400 mL (20 mL/kg) fluid bolus via an IO needle in the proximal tibia of this child. (4 marks)

(d) The child is conscious and distressed. Describe your pain management strategy for IO infusion. (6 marks)

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Model Answer:

(a) Justification for IO access (4 marks):

1. Time-critical emergency - Septic shock requires immediate fluid resuscitation (within 15 minutes) to restore perfusion and prevent irreversible organ damage [1 mark]

2. Failed peripheral IV access - Two attempts failed, further attempts will delay resuscitation; IO access provides rapid reliable alternative (success rate >90% in less than 90 seconds) [1 mark]

3. Pharmacokinetic equivalence - All resuscitation medications and fluids administered via IO route have equivalent bioavailability and onset times to IV route [1 mark]

4. Guideline recommendation - APLS and ARC Guidelines recommend IO access after 2 failed IV attempts or 90 seconds in pediatric emergencies [1 mark]

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(b) Pharmacokinetics IO vs IV (6 marks):

Absorption and Distribution (3 marks):

• Bioavailability: 90-100% for all drugs tested (equivalent to IV) - marrow sinusoids drain directly into central venous circulation [1 mark]

• Time to central circulation: IO slightly delayed vs IV (tibial IO 40-60 seconds vs IV 20-30 seconds), but clinically insignificant in cardiac arrest [1 mark]

• Peak plasma levels (Cmax): Equivalent for all resuscitation drugs (epinephrine, atropine, amiodarone, sodium bicarbonate, antibiotics) [1 mark]

Clinical Implications (3 marks):

• No dose adjustment required - Same doses as IV route for all medications [1 mark]

• All IV drugs/fluids permissible - Crystalloids, colloids, blood products, vasopressors, antibiotics, anesthetics all safe and effective [1 mark]

• Site matters - Humeral IO 15-30 seconds faster than tibial IO due to proximity to central circulation (humeral head preferred in adult cardiac arrest, but tibia preferred in pediatrics due to easier landmarks) [1 mark]

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(c) Fluid bolus delivery technique (4 marks):

Equipment (1 mark):

• 60 mL syringe, 3-way tap, 0.9% saline bag [0.5 mark]
• OR pressure bag set to 300 mmHg [0.5 mark]

Technique - 60 mL syringe push (preferred pediatrics) (2 marks):

1. Attach 60 mL syringe to 3-way tap connected to IO line [0.5 mark]

2. Withdraw 60 mL from saline bag into syringe [0.5 mark]

3. Push 60 mL via IO over 2-3 minutes (manual pressure) [0.5 mark]

4. Repeat 6-7 times to deliver 400 mL (20 mL/kg) total over 15-20 minutes [0.5 mark]

Alternative - Pressure bag technique (1 mark):

• Connect saline bag to IV tubing and IO line
• Apply pressure bag at 300 mmHg
• Infuse 400 mL over 10-15 minutes (flow rate ~150-200 mL/h with pressure) [Award 1 mark if pressure bag described correctly]

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(d) Pain management strategy for conscious patient (6 marks):

Problem Identification (2 marks):

• IO infusion causes severe pain in conscious patients due to increased intramedullary pressure from fluid infusion [1 mark]
• Insertion through periosteum stimulates periosteal nerve fibers (sharp pain during drilling) [0.5 mark]
• Pain is disproportionate to injury and can cause patient distress, combativeness, and dislodgement of IO needle [0.5 mark]

Lidocaine Protocol (3 marks):

1. Calculate dose: 0.5 mg/kg = 0.5 × 20 kg = 10 mg lidocaine [0.5 mark]

   • Use 2% preservative-free lidocaine = 0.5 mL of 2% solution [0.5 mark]

2. Administer: Push 10 mg lidocaine slowly via IO route over 60-120 seconds (NOT bolus) [0.5 mark]

3. Wait: 60 seconds for lidocaine to diffuse through marrow [0.5 mark]

4. Flush: 5-10 mL 0.9% saline to distribute lidocaine [0.5 mark]

5. Commence fluid bolus: Pain should be minimal; if pain persists, give additional 5 mg lidocaine [0.5 mark]

Alternative Analgesia (1 mark):

• IV sedation if IV access subsequently secured: Fentanyl 1 mcg/kg IV (20 mcg) OR ketamine 0.25-0.5 mg/kg IV (5-10 mg) [0.5 mark]
• Intranasal analgesia if no IV: Fentanyl 1.5 mcg/kg IN (30 mcg = 0.06 mL of 500 mcg/mL) OR ketamine 3 mg/kg IN (60 mg = 0.6 mL of 100 mg/mL) [0.5 mark]

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Viva Scenarios

Viva Scenario 1: IO Access in Cardiac Arrest

Scenario:

You are the ICU registrar called to the emergency department to assist with a 70-year-old man in cardiac arrest. The patient has been in VF for 5 minutes. The paramedics have performed high-quality CPR and defibrillated twice. The ED resident has made three unsuccessful attempts at peripheral IV cannulation. The team leader asks you to obtain vascular access.

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Examiner Questions and Model Answers:

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Q1: What is your immediate approach to vascular access in this patient?

A1: This patient requires immediate vascular access for medication administration (epinephrine) during cardiac arrest. After three failed IV attempts, the next step is intraosseous (IO) access, which is the recommended second-line vascular access in cardiac arrest per ARC Guideline 11.5.

I would select the proximal humerus as the preferred site in an adult cardiac arrest because:

• Higher flow rates than tibia (150-250 mL/min vs 90 mL/min)
• Faster drug delivery to central circulation (20-30 seconds vs 40-60 seconds)
• Accessible during chest compressions without interfering with CPR
• Equivalent pharmacokinetics to IV for all resuscitation drugs

If humeral access fails or is not feasible, I would use the proximal tibia (2 cm below tibial tuberosity, medial aspect) as an alternate site.

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Q2: Describe the insertion technique for humeral IO access in this patient.

A2:

Anatomical landmarks:

• Patient position: Arm adducted with hand resting on abdomen (internally rotates shoulder to expose greater tubercle)
• Location: Greater tubercle of humerus, 1-2 cm below acromion process
• Insertion angle: 45° medial angulation toward glenoid fossa

Insertion steps:

1. Palpate landmarks - Feel acromion, move 1-2 cm inferior, identify greater tubercle prominence

2. Apply antiseptic - 2% chlorhexidine (brief wipe, do NOT delay for drying in arrest)

3. Attach 25 mm (blue) needle to EZ-IO drill, remove rubber cap

4. Position needle at 45° angle medial toward glenoid fossa (NOT perpendicular)

5. Apply firm downward pressure while drilling - Continue until sudden loss of resistance (cortical breach at ~20-30 mm depth)

6. Remove drill, remove stylet - Needle should stand upright

7. Aspirate marrow (if time permits) - Dark blood confirms placement

8. Flush 5-10 mL saline - No resistance, no swelling confirms correct placement

9. Secure with dressing, connect to resuscitation drugs

Total time: 30-60 seconds

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Q3: You successfully insert the humeral IO and administer 1 mg epinephrine. How does epinephrine pharmacokinetics via IO compare to IV?

A3:

Pharmacokinetics IO vs IV:

• Bioavailability: 90-100% (equivalent to IV) - bone marrow sinusoids drain directly into central venous circulation

• Time to central circulation:

  • "Humeral IO: 20-30 seconds"
  • "Tibial IO: 40-60 seconds"
  • "Peripheral IV: 20-30 seconds"
  • Humeral IO is equivalent to peripheral IV

• Peak plasma concentration (Cmax): Equivalent to IV

• Dose: Same as IV (1 mg epinephrine every 3-5 minutes in adult cardiac arrest)

Evidence: Santos et al (2012, PMID: 22520796) compared IO vs IV epinephrine in out-of-hospital cardiac arrest and found no significant difference in pharmacokinetics or resuscitation outcomes.

Clinical implications:

• No dose adjustment required
• Flush with 10-20 mL saline after each drug to propel into central circulation
• Slightly longer circulation time than IV (10-20 seconds) but clinically insignificant

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Q4: Return of spontaneous circulation (ROSC) is achieved. The patient is transferred to ICU. When should you remove the IO line, and what are the risks of prolonged IO use?

A4:

Timing of IO removal:

• Ideal: Remove within 24 hours once alternative IV/CVC access secured
• Maximum: 48-72 hours (increased complication risk beyond 24 hours)
• This patient: Remove as soon as patient stabilized in ICU and CVC inserted (within 1-2 hours of ROSC)

Risks of prolonged IO use:

1. Osteomyelitis (most serious long-term complication):

   • Incidence: 0.4% if removed under 24 hours, 2-3% if >48 hours
   • Mechanism: Bacterial inoculation during insertion or via catheter
   • Prevention: Strict asepsis during insertion, remove promptly, avoid if skin infection

2. Compartment syndrome:

   • Incidence: 0.6-1% overall
   • Mechanism: Extravasation from dislodgement or malposition
   • Recognition: Pain, swelling, firm compartment, neurovascular compromise
   • Prevention: Secure needle carefully, check site regularly, minimize limb movement

3. Skin necrosis:

   • Mechanism: Prolonged use >72 hours, extravasation of vasopressors
   • Prevention: Remove promptly, avoid infusing vasopressors via IO if possible

4. Fracture (rare):

   • Risk increases with patient movement, osteoporotic bone
   • Prevention: Secure needle, minimize movement, gentle removal technique

Monitoring in ICU:

• Check IO site every 4 hours for swelling, redness, pain
• Transition to CVC as soon as hemodynamically stable
• Remove IO and apply pressure dressing

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Q5: What are the contraindications to IO access at a specific site?

A5:

Absolute contraindications at a specific site:

1. Fracture at insertion site - Risk of extravasation through fracture line, impaired marrow cavity

2. Previous IO attempt same bone under 48 hours - Risk of extravasation through prior puncture site

3. Cellulitis or skin infection at insertion site - Risk of osteomyelitis from introducing bacteria

4. Compartment syndrome in that limb - Extravasation will worsen compartment pressure

5. Bone disease (osteogenesis imperfecta, osteopetrosis, severe osteoporosis) - Risk of fracture

Relative contraindications:

• Prosthetic joint or orthopedic hardware at site (use alternate site)
• Recent orthopedic surgery same bone (use alternate site)
• Overlying burn or tissue injury (increased infection risk)

NOT contraindications:

• Age (safe in all ages from neonates to elderly)
• Cardiac arrest (IO is indicated)
• Coagulopathy (relative - apply pressure longer post-removal, but do NOT delay in arrest)

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Viva Scenario 2: Paediatric IO Access and Complications

Scenario:

You are the ICU consultant supervising a junior registrar in the emergency department. A 2-year-old child (12 kg) presents with suspected meningococcal sepsis with a non-blanching purpuric rash, capillary refill time 6 seconds, HR 180 bpm, BP 60/30 mmHg. The ED resident has failed two attempts at peripheral IV cannulation. The registrar asks for your guidance on obtaining vascular access.

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Examiner Questions and Model Answers:

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Q1: What vascular access would you recommend, and why?

A1: I would recommend proximal tibial intraosseous (IO) access for this child because:

Indications:

• Time-critical septic shock requiring immediate fluid resuscitation (target 20 mL/kg within 15 minutes)
• Failed peripheral IV access (2 attempts) - further attempts will delay life-saving treatment
• High success rate (>90%) with rapid insertion time (less than 90 seconds) in pediatric patients

Site selection - proximal tibia preferred in pediatrics:

• Easier landmarks than humerus in young children
• Familiar technique for most clinicians
• Safe distance from growth plate (≥2 cm distal to physis minimizes growth plate injury risk)
• Accessible in supine position during resuscitation

Alternative: If proximal tibia fails or is contraindicated (fracture, infection), use:

• Distal tibia (2 cm above medial malleolus) in children >6 years
• Humeral head if child >40 kg (landmarks difficult under 40 kg)

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Q2: Describe the insertion technique for proximal tibial IO access in this 2-year-old child, including equipment selection.

A2:

Equipment selection:

• Device: EZ-IO powered drill (preferred) or manual Jamshidi needle if powered device unavailable
• Needle size: 15 mm (pink) needle - child under 40 kg (12 kg), minimal tissue depth
• Confirm size: Palpate bone - if easily palpable through skin, 15 mm adequate

Insertion technique:

1. Position: Supine with rolled towel behind knee, leg extended and externally rotated slightly

2. Landmarks:

   • Palpate tibial tuberosity (bony prominence below patella)
   • Move 2 cm (1 fingerbreadth in 2-year-old) distal and medial
   • Identify flat medial tibial surface

3. Antisepsis: 2% chlorhexidine, brief wipe (do NOT delay)

4. Needle insertion:

   • Position needle perpendicular to bone (90° angle) or slightly caudad (away from growth plate)
   • Apply firm downward pressure while activating drill
   • Continue until sudden loss of resistance (usually 10-15 mm depth in 2-year-old)

5. Remove drill and stylet

6. Confirm placement:

   • Aspirate marrow (dark blood with particles) - send for glucose, lactate if needed
   • Flush 5 mL saline - no resistance, no swelling confirms correct placement

7. Secure: Transparent dressing, pad hub with gauze

Time: 30-60 seconds from preparation to secured access

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Q3: How would you deliver a 240 mL (20 mL/kg) fluid bolus via the IO in this child?

A3:

Method: 60 mL syringe push technique (preferred for pediatric fluid boluses)

Equipment:

• 60 mL syringe
• 3-way tap
• 0.9% saline 1000 mL bag

Technique:

1. Attach 3-way tap to IO line, connect syringe and saline bag via 3-way tap ports

2. Withdraw 60 mL from saline bag into syringe

3. Close tap to saline bag, open tap to IO line

4. Push 60 mL manually over 2-3 minutes (firm, steady pressure)

5. Repeat 4 times to deliver 240 mL total (4 × 60 mL = 240 mL)

Total time: 10-15 minutes for full bolus

Rationale: Manual syringe push provides:

• Faster delivery than pressure bag in small children (veins may collapse under high pressure)
• Controlled infusion - can monitor for extravasation
• Immediate availability - no need to find/set up pressure bag

Alternative - Pressure bag:

• Set pressure bag to 300 mmHg
• Connect saline bag to IV tubing and IO line
• Infuse 240 mL over 10-15 minutes
• Disadvantage: May be slower in small children, requires pressure bag equipment

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Q4: Thirty minutes after IO insertion, you notice swelling and firmness in the anterior compartment of the child's lower leg. What is your diagnosis and management?

A4:

Diagnosis: Compartment syndrome secondary to IO extravasation

Mechanism:

• Extravasation of fluid from malpositioned IO needle (not fully in marrow cavity)
• OR dislodgement of needle during resuscitation
• Fluid accumulates in anterior compartment → increased compartment pressure → vascular compromise

Recognition:

• Early signs (present in this case):

  • Swelling and firmness of compartment
  • Pain (child may be irritable, crying)
  • Tense compartment on palpation

• Late signs (indicate irreversible damage):

  • Pallor, pulselessness, paresthesia, paralysis
  • Loss of distal pulses (dorsalis pedis, posterior tibial)

Immediate Management:

1. Stop IO infusion immediately - Disconnect IV tubing

2. Remove IO needle - Pull out with gentle traction, apply pressure to site

3. Elevate limb to heart level (NOT above - reduces arterial inflow)

4. Measure compartment pressure (if available):

   • 30 mmHg = diagnostic for compartment syndrome

   • 20 mmHg with clinical signs = concerning

5. Urgent surgical consultation - Orthopedic or general surgery

6. Analgesia - Fentanyl 1 mcg/kg IV (if IV access secured) or intranasal 1.5 mcg/kg

7. Monitor neurovascular status every 15 minutes:

   • Pulses, capillary refill, sensation, movement

Definitive Management:

• Emergency fasciotomy if compartment pressure >30 mmHg or clinical diagnosis confirmed
• Time-critical: Perform within 6 hours to prevent permanent neuromuscular damage
• Four-compartment fasciotomy (anterior, lateral, superficial posterior, deep posterior)

Prevention:

• Confirm correct IO placement before infusion (flush test)
• Secure IO needle carefully to prevent dislodgement
• Monitor insertion site regularly for swelling

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Q5: The child is conscious during your assessment. How would you manage pain associated with IO infusion?

A5:

Pain Management Strategy:

Problem: IO infusion in conscious children causes severe pain from:

• Periosteal nerve stimulation during insertion
• Increased intramedullary pressure from fluid infusion

Intraosseous Lidocaine Protocol (Preferred):

1. Calculate dose: 0.5 mg/kg = 0.5 × 12 kg = 6 mg lidocaine

   • Use 2% preservative-free lidocaine = 0.3 mL of 2% solution

2. Administer: Push 6 mg (0.3 mL) lidocaine slowly via IO over 60-120 seconds

3. Wait 60 seconds for lidocaine to diffuse through marrow

4. Flush: 5 mL 0.9% saline to distribute lidocaine

5. Commence fluid bolus: Pain should be minimal

Alternative Analgesia (if lidocaine ineffective or unavailable):

• Intranasal fentanyl: 1.5 mcg/kg = 18 mcg IN (0.036 mL of 500 mcg/mL)

  • Rapid onset (5-10 min), effective for procedure

• Intranasal ketamine: 3 mg/kg = 36 mg IN (0.36 mL of 100 mg/mL)

  • Analgesic + dissociative, preserves airway reflexes

• IV sedation (if IV subsequently secured): Fentanyl 1 mcg/kg IV OR ketamine 0.25-0.5 mg/kg IV

Monitoring:

• Monitor for respiratory depression with opioids (have naloxone available)
• Reassure child and family
• Minimize procedural distress