Intraosseous (IO) Access

Intraosseous (IO) access is an emergency vascular access technique that delivers fluids and medications directly into the bone marrow cavity. The bone marrow contains a rich network of venous sinusoids that drain directly into the central circulation, providing a reliable "non-collapsible" IV when peripheral veins are inaccessible.

Why IO Works

• Direct vascular access: Marrow sinusoids connect directly to central venous circulation
• Non-collapsible: Unlike veins, the bone marrow space doesn't collapse in shock
• Equivalent to IV: Drug absorption and onset times match intravenous delivery
• Rapid placement: Insertion takes 10-30 seconds with modern devices

Visualizing How IO Works

Historical Context

IO access was first described in 1922 and used extensively during World War II for battlefield resuscitation. After declining in favor of IV access, it experienced a renaissance in the 1980s with improved devices. Today, IO is considered equivalent to IV by AHA/ACLS guidelines and is the preferred alternative when IV access fails.

Emergency Indications

• Cardiac arrest – IO is first-line when IV not immediately available
• Severe shock – Hemorrhagic, septic, anaphylactic, or cardiogenic
• Major trauma – When peripheral veins are collapsed or inaccessible
• Severe dehydration – Especially in pediatric patients
• Status epilepticus – When IV access cannot be established
• Burns – When extremities are unavailable for peripheral access

Clinical Criteria for IO Use

• Failed IV attempts: 2 failed attempts OR 90 seconds without success
• Difficult access conditions: Obesity, edema, IV drug use history, vasculopathy
• Time-critical situations: When medication delivery cannot wait

What Can Be Administered via IO?

• All ACLS medications (epinephrine, amiodarone, lidocaine, etc.)
• Blood products (PRBCs, plasma, platelets)
• Crystalloid fluids (NS, LR)
• Vasopressors and inotropes
• Sedatives and analgesics
• Contrast media for CT imaging
• Antibiotics

Absolute Contraindications

• Fracture at insertion site – Fluid will extravasate through fracture
• Previous IO attempt in same bone (within 48 hours) – Risk of extravasation
• Overlying infection/cellulitis – Risk of osteomyelitis
• Prosthetic limb or joint at site
• Inability to identify landmarks

Relative Contraindications

• Osteoporosis – Increased risk of fracture, but not absolute
• Osteogenesis imperfecta – Brittle bone disease
• Osteopetrosis – Abnormally dense bone may prevent insertion
• Recent orthopedic surgery at the site
• Significant burns at insertion site
• Peripheral vascular disease – May affect perfusion

Site-Specific Contraindications

Power-Driven: EZ-IO (Arrow/Teleflex)

The most widely used IO device in modern emergency medicine. Battery-powered driver with disposable needle sets.

EZ-IO Needle Sizes

Spring-Loaded Devices

Bone Injection Gun (BIG)

• Disposable, single-use spring-loaded device
• Available in adult and pediatric sizes
• Set depth before insertion
• Pull safety, position, press trigger

FAST1 (First Access for Shock and Trauma)

• Designed specifically for sternal access in adults
• Multiple needle cluster penetrates manubrium
• Includes integrated target patch for landmark identification
• Not recommended during active CPR

Manual IO Needles

• Jamshidi needle – Most common manual needle
• Sur-Fast needle – Threaded design for stability
• Dieckmann needle – Shorter, designed for pediatrics

Manual needles require more force and technique. Best suited for pediatric patients with softer cortical bone. Less commonly used in adults due to dense cortex.

1. Proximal Humerus (Adult Preferred Site)

Landmarks

• Patient supine, arm adducted and internally rotated (hand on umbilicus)
• Palpate the greater tubercle – the bony prominence at the lateral shoulder
• Insertion site: 1-2 cm above the surgical neck
• Insert at 45° angle toward opposite hip

2. Proximal Tibia (Pediatric Preferred / Adult Alternative)

Landmarks

• Patient supine with knee slightly flexed (rolled towel under knee)
• Identify tibial tuberosity (bump below patella)
• Adult: 2 finger-breadths (2cm) below tuberosity, 1-2cm medial to tibial ridge
• Pediatric: 1 finger-breadth below tuberosity on flat anteromedial surface
• Insert at 90° to bone surface (perpendicular)

3. Distal Tibia

Landmarks

• Medial malleolus – the bony prominence at inner ankle
• Insertion site: 1-2cm proximal to medial malleolus
• Flat surface of distal tibial metaphysis
• Insert at 90° to bone surface

4. Distal Femur (Pediatric Alternative)

Landmarks

• Patient supine with knee slightly flexed
• Palpate patella and femoral condyles
• Insertion site: 1-2cm above patella on midline
• Insert at 10-15° angle toward head (into marrow cavity)

Site Selection Summary

Pre-Procedure

1. Confirm indication – Failed IV, cardiac arrest, critical patient
2. Check contraindications – No fracture, no prior IO, no infection at site
3. Select site – Proximal humerus (adult) or proximal tibia (pediatric)
4. Select needle size – Based on patient weight and tissue depth
5. Assemble equipment:
   • EZ-IO driver with appropriate needle
   • EZ-Stabilizer dressing
   • Extension tubing with Luer-lock
   • 10mL saline flush syringe
   • 2% lidocaine (40mg) for conscious patients
   • Pressure bag or infusion pump

EZ-IO Insertion Technique

1. Position patient – Stabilize the limb; supine for most sites
2. Clean insertion site – Antiseptic swab (chlorhexidine or alcohol)
3. Stabilize the limb – Hold firmly but don't wrap hand around insertion site
4. Remove safety cap from needle set
5. Insert needle through skin to bone surface
   • Proximal humerus: 45° angle toward opposite hip
   • Tibia: 90° perpendicular to bone surface
6. Confirm position – Needle should rest on bone, 5mm black line visible
7. Squeeze trigger – Advance until hub reaches skin OR you feel "pop"
8. Stop drilling when loss of resistance felt
9. Stabilize hub and remove driver by pulling straight back
10. Remove stylet by turning counterclockwise

Confirmation of Placement

• Needle stands upright without support
• Aspirate bone marrow – Dark, thick blood (may not always be present)
• Flush with 10mL saline – Should flow freely without resistance
• No extravasation – No swelling around site

Post-Insertion

1. Apply EZ-Stabilizer or secure with tape
2. Connect extension tubing with Luer-lock
3. Lidocaine 2% – Slow push 20-40mg for conscious patients (wait 30-60 sec)
4. Begin infusion – Pressure bag for bolus fluids
5. Monitor site – Check for compartment syndrome signs
6. Document – Time, site, needle size, confirmation methods

Flow Rate by Site (Under Pressure)

Optimizing Flow

• Pressure infusion – Always use 300mmHg pressure bag for bolus fluids
• Warm fluids – Cold fluids increase marrow resistance
• Prime with flush – Initial 10mL saline flush opens sinusoids
• Avoid air – Prime tubing completely; air embolism possible

Proximal Humerus Infusion Demonstration

Medication Administration

• Follow all medications with flush – 5-10mL saline push
• Drug onset equivalent to IV – No dose adjustment needed
• Vasopressors – Safe to administer; flush well after
• Blood products – Require pressure; may take longer but effective

Overall Complication Rate

IO access has a remarkably low complication rate (<1%) when performed correctly. Most complications are minor and related to technique errors that can be avoided with proper training.

Immediate Complications

Delayed Complications

Rare Complications

Site Selection in Children

• Proximal tibia – First choice for all pediatric ages
  • 1 finger-breadth below tibial tuberosity
  • Flat anteromedial surface
  • Insert 90° perpendicular to bone
• Distal tibia – Alternative site
  • 1-2 cm proximal to medial malleolus
  • Flat medial surface
• Distal femur – Alternative for infants
  • Anterior surface, 1 cm above patella
  • 10-15° cephalad angle

Needle Selection by Weight

Pediatric-Specific Technique Tips

• Support the extremity – Pediatric bones are more flexible
• Less force required – Cortex is thinner than adults
• Manual needles viable – Some prefer Jamshidi needles in infants
• Confirm placement carefully – Small marrow cavity, less marrow to aspirate

Fluid and Medication Dosing

• Lidocaine for conscious child: 0.5 mg/kg (max 40mg)
• Fluid bolus: 20 mL/kg; may repeat x3
• Epinephrine (arrest): 0.01 mg/kg (0.1 mL/kg of 1:10,000)
• All medications follow with 5 mL flush

Growth Plate Considerations

• The growth plate (physis) is located at the ends of long bones
• Proper IO sites are on the metaphysis, away from the physis
• Proximal tibia site naturally avoids growth plate
• No documented cases of growth disturbance from proper IO placement

Core Concepts

• IO access provides IV-equivalent drug and fluid delivery
• Onset and absorption times match intravenous administration
• Use when IV access fails after 2 attempts or 90 seconds
• First-line alternative access in cardiac arrest and critical shock

Site Selection Summary

• Adults: Proximal humerus (fastest flow) or proximal tibia
• Pediatrics: Proximal tibia (first choice) or distal tibia
• Avoid: Fractured bones, prior IO site, infected tissue

Procedure Essentials

• EZ-IO: Insert needle to bone surface, drill until loss of resistance
• Confirm: Needle stability, marrow aspirate, flush without resistance
• Lidocaine first for conscious patients (40mg adults, 0.5mg/kg peds)
• Use pressure bag for bolus fluids
• Remove within 24 hours

Critical Numbers

Guidelines

1. American Heart Association. Advanced Cardiovascular Life Support (ACLS) Provider Manual. 2020.
2. American Heart Association. Pediatric Advanced Life Support (PALS) Provider Manual. 2020.
3. Teleflex. Arrow EZ-IO Intraosseous Vascular Access System. Instructions for Use. 2023.

Key Studies & Reviews

4. Petitpas F, et al. "Use of intra-osseous access in adults: a systematic review." Crit Care. 2016;20:102.
5. Pasley J, et al. "Intraosseous infusion rates under high pressure: A comparison of the FAST1, EZ-IO, and BIG." Prehosp Emerg Care. 2015;19(1):117-122.