Intraosseous (IO) Access

IO access gives a route for drugs and fluids when IV access fails or is not feasible. Delay in placement is the main danger in arrest and shock.

IO access puts a needle through the cortex of a long bone and into the marrow cavity. Marrow venous sinuses drain into the central circulation. So drugs and fluids given into the marrow reach the heart without a peripheral vein. This page covers the powered EZ-IO method from the manufacturer procedure template. Spring-loaded and sternal devices are outside it.

How It Works

• Entry: Skin and cortex go first. The EZ-IO driver then advances the needle into the marrow space.
• Circulation: The marrow sinuses empty into the central venous system. That is why the route works.
• Dosing: Same dose, same rate, same concentration as a peripheral IV.
• Pressure: Infuse under pressure for optimal flow. Check patency before each infusion.
• Limit: The template authorizes IO use for up to 24 hours. Plan the switch to conventional IV access.

Where It Fits

The 2025 AHA Guidelines for CPR and ECC, Part 9 (adult advanced life support), put IV access first for drugs in cardiac arrest (COR 1, LOE A). IO gets a reasonable rating once initial IV attempts are unsuccessful or not feasible (COR 2a, LOE A). PARAMEDIC-3 is a UK randomized trial of 6,082 adults in cardiac arrest. Starting with IO or with IV gave similar 30-day survival (4.5% vs 5.1%, adjusted odds ratio 0.94, 95% CI 0.68–1.32). Any return of spontaneous circulation came in lower for IO-first (36.0% vs 39.1%, adjusted odds ratio 0.86, 95% CI 0.76–0.97). It was a secondary outcome, and it was not adjusted for multiplicity. For children, Part 8 (section 7.1) of the same 2025 AHA set asks for rapid IV or IO access for drugs in cardiac arrest (COR 1, LOE C-LD). The first route is picked on availability, expertise and timeliness (COR 1, LOE C-EO). The 2025 ILCOR consensus applies too. Sizing here begins at the template's 3 kg. Local protocol sets the IO trigger.

Indications

• Cardiac arrest when IV access is unsuccessful or not feasible
• Shock or major trauma after the failed-IV trigger in your protocol
• Pediatric resuscitation or shock when IV access is not obtained promptly under local protocol
• Time-critical drug or fluid delivery that cannot wait for an IV

Absolute Contraindications

• Fracture in the target bone
• Infection at the insertion site
• Prior IO or attempted IO in the same bone within 48 hours
• Orthopedic surgery at the site, or a prosthetic limb or joint
• No landmarks: excessive tissue (severe obesity) or inadequate anatomic landmarks

Relative Contraindications & Cautions

• Excess soft tissue: Excess tissue at any site: use the longer 45 mm needle, or choose another site.
• Awake patient in pain: Pain does not rule it out. Pre-treat with lidocaine (Medications & Settings).

Consider an Alternative

When the bone or site is unusable, your protocol sets the next access route. See IV Insertion.

Abort / Stop Criteria

• Flush resists or causes swelling: Stop, remove the needle, re-site.
• Needle loose or cannot be stabilized: Re-site.
• Fracture or prior IO in the same bone found: Choose another site.

Team Roles During the Procedure

• Operator: Selects the site and needle, inserts and drills.
• Limb stabilizer: Holds the limb steady and keeps the arm or leg in position.
• Medication clinician: Prepares lidocaine, flushes and drugs at the IV dose.
• Monitor and recorder: Times the attempt, records depth check, flush result and totals.

Local protocol and operator experience pick the site. The manufacturer template lists the adult sites but does not rank them.

1. Proximal Humerus

1. Position the arm: Place the hand on the abdomen with the arm close to the body, which rotates the humerus internally.
2. Find the landmark: Palpate the greater tubercle down to the surgical neck; the site is 1–2 cm above the neck.
3. Set the angle: Point the needle 45° to the anterior plane, angled posteromedially.
4. Check depth: Touch the tip to bone and confirm the 5 mm line is visible above the skin before drilling.

Pediatric

For infants and children, the template uses the same proximal humerus landmarks. Needle size follows weight (see Special Populations).

2. Proximal Tibia

1. Extend the leg: Keep the knee straight.
2. Find the landmark: Adult: about 2 cm medial to the tibial tuberosity, or 3 cm below the patella and 2 cm medial.
3. Set the angle: Aim 90° to the bone on the flat anteromedial surface.
4. Check depth: Confirm the 5 mm line before drilling.

Pediatric

In children, aim about 1 cm medial to the tuberosity. Or go just below the patella (about 1 cm) and slightly medial (about 1 cm). Pinch the tibia to find its borders, and stay on the flat anteromedial surface.

3. Distal Tibia

1. Find the malleolus: Locate the medial malleolus.
2. Find the landmark: Adult: about 3 cm proximal to the malleolus.
3. Confirm the surface: Palpate the anterior and posterior borders to confirm the flat centre of the bone.
4. Set the angle and depth: Aim 90° and confirm the 5 mm line before drilling.

Pediatric

In children, the site sits about 1–2 cm proximal to the medial malleolus. The rest of the technique is the same.

4. Distal Femur (Children)

1. Straighten the leg: Keep the knee straight so it cannot bend.
2. Find the landmark: Palpate the patella; the site is just proximal to it (no more than 1 cm) and 1–2 cm medial to midline.
3. Set the angle: Aim 90° to the bone and confirm the 5 mm line before drilling.
4. Secure: Keep the leg straight on a board after insertion.

Equipment

• EZ-IO power driver and needle sets (15, 25 and 45 mm; see sizing)
• EZ-Connect extension set (priming volume about 1.0 mL)
• EZ-Stabilizer dressing
• Luer-lock syringe with sterile normal saline: 5–10 mL adult; 2–5 mL infant or child
• 2% preservative-free, epinephrine-free lidocaine for awake patients, per protocol
• Infusion pressure bag or pump, tubing and a 3-way stopcock
• Gloves, cleansing agent and sharps block

Sizing

Patient Positioning & Preparation

Position the patient supine. For the proximal humerus, place the arm across the abdomen. For the distal femur, keep the leg straight. Prime the extension set with lidocaine for an awake patient, or with saline for an unresponsive patient, before attaching it to the hub.

Treat these as typical adult and pediatric references. Confirm them against local protocol and current drug labeling. Doses vary by protocol; follow local protocols and medical direction.

Phase 1: Prepare

1. Confirm the indication: IV access has failed the local trigger, or IV is not feasible in an urgent patient.
2. Check contraindications: No fracture, infection, orthopedic hardware, or IO in the same bone within 48 hours.
3. Choose the site and needle: Follow local protocol and operator experience for the site (adult sites: proximal humerus, proximal tibia, distal tibia); size the needle by weight and tissue depth (Anatomy & Landmarks).
4. Prime the extension set: Lidocaine if the patient is awake and responsive to pain; saline if not.

Phase 2: Perform

5. Position and clean: Stabilize the limb with your hand clear of the insertion site and needle path. Clean the site per protocol, using aseptic technique.
6. Locate the landmarks: Palpate the site as described in Anatomy & Landmarks.
7. Attach the needle set: Connect it to the driver and remove the safety cap.
8. Set the angle and depth: Press gently until the tip touches bone and the 5 mm line is visible above the skin.
9. Drill: Squeeze the trigger and apply gentle, steady pressure. Release the trigger when the hub reaches the skin or you feel a sudden loss of resistance; do not keep drilling.

10. Stabilize the hub: Hold the hub steady, remove the driver, and place the stylet in a sharps container.
11. Dress the site: Place the EZ-Stabilizer dressing over the hub.
12. Connect the extension set: Attach the primed set and keep the clamp open.

Phase 3: Confirm & Secure

13. Flush to confirm: Flush 5–10 mL (adult) or 2–5 mL (child) of saline. It must run without resistance or swelling (see Confirmation & Monitoring).
14. Treat pain if awake: Lidocaine per the Medications table, with a 60-second dwell before flushing.
15. Infuse under pressure: Verify patency before each drug or fluid. Give drugs at the IV dose and rate.
16. Secure and monitor: Immobilize the limb, check the site and limb, and document the time and details.

Primary Confirmation

The needle stays put, and a saline flush runs with no resistance and no swelling. This flush test is the primary check. Repeat it before each infusion.

Secondary Confirmation

• Site: No swelling, leakage or fluid under the skin around the hub.
• Dressing: EZ-Stabilizer secure and the extension set clamp open.
• Aspirate: Marrow may or may not come back. No aspirate does not mean failure.

Ongoing Monitoring

• Before every infusion: Verify patency with a flush.
• At each reassessment: Check the site and limb for swelling, pain, pallor and pain on passive movement.
• Replacement: The template authorizes IO use for up to 24 hours. Plan the switch to IV access.

Pediatrics

The template's 15 mm range starts at about 3 kg, so a neonate under 3 kg falls outside this table. Newborns who need emergency vascular access: the 2025 AHA Guidelines for CPR and ECC, Part 5 (neonatal resuscitation), recommend an umbilical vein catheter (COR 1, LOE C-LD). Intraosseous devices can help when IV access fails or is not feasible (COR 2a, LOE C-LD). The template says nothing about sizing neonatal devices. Use the neonatal device set and local protocol.

• Guideline: 2025 AHA Guidelines for CPR and ECC, Part 8, section 7.1: rapid IV or IO access is recommended for drugs in infants and children in cardiac arrest (COR 1, LOE C-LD). The initial route (IV or IO) depends on availability, expertise and timeliness (COR 1, LOE C-EO). Follow local protocol for the sequence.
• Sites: For children, the template lists the proximal humerus, proximal tibia, distal tibia and distal femur.
• Lidocaine (awake child): 0.5 mg/kg IO, max 40 mg first dose, then half the first dose; see Medications.
• Fluid boluses: 10–20 mL/kg with reassessment after each bolus.
• Sizing and dosing: See Equipment Sizing, Weight-Based Dosing and Pediatric Vascular Access.

Obesity

• Extra tissue may call for the 45 mm needle or a different site.
• No palpable landmarks in severe obesity: that counts as a contraindication.

Physiologically Difficult Patients

• In shock, infuse under pressure. Flow depends on the pressure you apply.
• Use caution with hypertonic, chemotherapy and vesicant drugs. A vesicant that leaks can injure soft tissue. Stop at the first swelling.

Immediate Aftercare

• Secure the limb: For the humerus, keep the arm across the abdomen or adducted; for the distal femur, keep the leg straight on a board.
• Dress the site: EZ-Stabilizer over the hub; extension set clamp open.

Ongoing Maintenance

• Verify patency before every infusion; monitor the site and limb.
• Removal: Remove the extension set and lift the dressing. Attach a sterile luer-lock syringe to the hub as a handle, rotate clockwise while pulling straight up. Do not rock or bend the catheter.

Transport Considerations

• Reassess the site and limb after every move.
• Keep the limb immobilized; do not reposition the arm or leg in transit without rechecking.
• Use the pressure bag or pump for every infusion.

Pearls

• Same drugs, same doses: IO drugs run at the IV dose, rate and concentration.
• The flush is the test: Placement is confirmed by a flush that runs with no resistance and no swelling. Aspirate is optional.
• Pressure for flow: Push it under pressure, and check patency before every infusion.
• Count the lidocaine: IO lidocaine counts toward the total on the lidocaine page.
• Clock the dwell: Note the insertion time. The template's ceiling is 24 hours, so plan the IV replacement.
• Check the line: The 5 mm black line confirms needle length before you drill.

Common Pitfalls

• Waiting too long for IV → go to IO at your protocol's trigger.
• Reusing the same bone within 48 hours → choose another site.
• Infusing into swelling → stop, remove the needle, re-site.
• Skipping lidocaine in an awake patient → pre-treat, then flush.
• Oversizing the needle in a child → size by weight and tissue depth.