What Is an Intraosseous Infusion Device?

The word "intraosseous" means inside the bone. An intraosseous infusion device is a specially designed needle system that is inserted through the hard outer layer of a bone (the cortex) and into the soft, spongy inner space called the bone marrow. The bone marrow is filled with a network of tiny blood vessels that connect directly to the body's main circulation, much like a large vein.

Once the needle is in place, fluids, blood products, and medicines can flow through the bone marrow and reach the bloodstream very quickly - often within seconds. This is why IO devices are used when there is no time to find a regular vein, or when veins have collapsed due to shock or severe illness.

IO access has been used in medicine since the 1930s. After a period of decreased use, it was rediscovered in the 1980s as a life-saving technique and has since become a standard tool in emergency care worldwide.

Where and When Are IO Devices Used?

IO devices are used in situations where intravenous (IV) access - placing a drip into a vein - cannot be achieved quickly enough or has failed. These include:

• Cardiac arrest (the heart has stopped beating)
• Severe shock from blood loss, severe infection, or burns
• Status epilepticus (prolonged, uncontrolled seizures)
• Anaphylaxis (life-threatening allergic reactions)
• Major trauma with collapsed or inaccessible veins
• Drowning, electrocution, or other critical emergencies
• Any situation where two or more attempts to place an IV have failed and the patient is critically ill

IO devices are used across many settings worldwide:

IO access is appropriate for all age groups, from premature newborns to older adults. However, because children - especially infants - are more likely to have veins that collapse during shock, IO devices are particularly common in pediatric emergency medicine.

Parts of an IO Device

While designs vary by type, most IO devices share these basic parts:

Types of Intraosseous Devices

There are three main categories of IO devices based on how they are inserted. Each has its own advantages, and availability may vary by country and institution.

Common Insertion Sites

IO needles can be placed in several bones of the body. The choice of site depends on the patient's age, size, and the clinical situation.

How to Use an IO Device: Step-by-Step

The general procedure for IO insertion follows these steps. Specific techniques may vary slightly based on the type of device used.

Step-by-Step: General IO Insertion Procedure

1. Confirm the indication: IO access is appropriate when IV access has failed after two attempts or cannot be achieved quickly enough in a critically ill patient.
2. Gather equipment: IO device (correct size for patient), antiseptic solution (chlorhexidine or povidone-iodine), gloves, IV extension set with a Luer-lock connection, syringes (5 mL and 10 mL), normal saline for flushing, securing/stabilising dressing, and a pressure bag or syringe for infusion.
3. Select the site: In children, the proximal tibia is usually first choice. Position the leg flat and slightly rotated outward. Locate the tibial tuberosity (the bump just below the kneecap) and measure 1-3 cm below it on the flat inner surface of the shin bone.
4. Prepare the site: Put on gloves. Clean the insertion site thoroughly with an antiseptic solution. Allow it to dry for at least 30 seconds.
5. Apply local anaesthetic (if patient is conscious): In conscious patients, a small amount of local anaesthetic (e.g. lidocaine 1%, without adrenaline) may be injected into the skin and down to the bone surface to reduce pain during insertion.
6. Insert the needle:
   • For manual needles: Position the needle at 90 degrees to the bone surface and use a firm twisting/screwing motion to push through the cortex. Stop when a sudden "give" or loss of resistance is felt - this means the needle has entered the marrow.
   • For battery-powered drill (EZ-IO): Place the needle tip against the bone at 90 degrees and activate the drill while applying gentle, steady pressure. Stop when resistance decreases.
   • For spring-loaded devices (BIG): Position correctly and release the spring mechanism as per manufacturer instructions.
7. Remove the stylet: Unscrew and remove the inner stylet. Attach a 5 mL syringe and gently aspirate. Aspirating bone marrow (a dark, blood-like fluid) confirms correct placement. Note: aspiration is not always successful even when the needle is correctly placed.
8. Confirm placement: Flush with 5-10 mL of normal saline. In conscious patients, lidocaine (0.5 mg/kg, preservative-free) should be flushed slowly first to reduce pain. Correct placement is confirmed when there is no swelling around the site, no resistance to flushing, and the patient's condition does not worsen.
9. Secure the needle: Apply the stabilising dressing included with the device (e.g. EZ-Stabiliser). The needle must be held firmly in place. Do not allow the needle to move or rotate after insertion.
10. Connect the IV line and begin infusion: Connect the IV extension set and begin infusing the required fluids or medications. Because bone marrow has a higher resistance than veins, a pressure bag (inflated to 300 mmHg) or infusion pump may be needed to achieve adequate flow rates.
11. Monitor continuously: Check the site frequently for signs of swelling, redness, or leakage (extravasation). Perform neurovascular checks on the limb - check circulation, sensation, and movement below the IO site.
12. Remove as soon as IV access is established: IO access is a temporary bridge. It should be removed once standard IV or central venous access is obtained, ideally within 24 hours and no longer than 48 hours.

Delivering Lidocaine for Pain (Conscious Patients)

When a conscious patient requires IO infusion, fluids and medications entering the bone marrow under pressure trigger severe pain. Before infusing, 0.5 mg/kg of 2% preservative-free lidocaine (without adrenaline) should be slowly flushed into the IO needle and allowed to sit for 60 seconds. This significantly reduces discomfort during the infusion.

Removing the IO Needle

To remove the IO needle, the IV extension set is detached. A 5 mL syringe is attached to the hub of the IO needle and used as a handle. The needle is pulled straight out with a firm, smooth motion - do not twist or rock the needle during removal. The site is then cleaned and covered with a sterile dressing. A follow-up neurovascular check of the limb is done after removal and at regular intervals for 24 hours.

What Can Be Given Through an IO Device?

Almost everything that can be given intravenously can also be given through an IO route. This includes:

Doses given by IO route are the same as IV doses. The onset of action is slightly slower than IV for some medications (for example, succinylcholine may take 50-60 seconds to act via IO compared to 30 seconds via IV), but is still significantly faster than other alternative routes.

Contraindications: When Should IO NOT Be Used?

There are situations where IO access at a particular site should be avoided:

Precautions and Potential Complications

IO devices are considered safe when used correctly, but complications can occur. Most are rare and preventable with proper technique and monitoring.

Complications to Watch For

General Precautions

• Always use strict sterile technique - clean gloves, clean site, sterile equipment.
• Never leave an IO needle in place for more than 24-48 hours. Remove it as soon as IV access is available.
• Do not use an IO site that has had a previous insertion attempt in the last 24-48 hours.
• Monitor the limb continuously - check colour, temperature, pulse, and sensation below the insertion site.
• Use correct needle size for the patient's size and tissue depth. Using too short a needle can mean the needle doesn't reach the marrow. Too long can penetrate the opposite cortex.
• Secure the needle firmly. An unsecured IO needle that moves or comes out during resuscitation interrupts treatment.
• Never use excessive force when inserting a manual needle - controlled pressure reduces the risk of fracture and over-penetration.

How to Select the Correct Needle Size

Needle length is important. Using a needle that is too short means it may not reach the bone marrow. A needle that is too long may penetrate through both sides of the bone. For battery-powered systems like the EZ-IO, colour-coded needles guide selection:

Always check the tissue depth over the intended insertion site before choosing needle length. The needle needs to pass through skin, subcutaneous tissue, and the bone cortex to reach the medullary (marrow) space. Clinical judgment and patient-specific anatomy guide final needle selection.

Device Safety and Storage

Proper storage and maintenance of IO devices ensures they function correctly in an emergency, when time is critical.

• Keep devices in a clean, dry location away from moisture, extreme heat, or direct sunlight.
• Check expiry dates regularly. IO needles are single-use, sterile devices. Expired products must never be used.
• Store battery-powered devices (e.g. EZ-IO driver) with a charged battery. Batteries should be tested or replaced at regular intervals as per the manufacturer's recommendations. A dead battery in an emergency renders the device unusable.
• Inspect packaging before use. If the sterile packaging is torn, punctured, or wet, the device should be discarded and replaced with a new one.
• Use only once. IO needles are single-use only. They must never be reused or re-sterilised. Reuse causes needle dulling, sterility failure, and patient safety risks.
• Keep spare needles in the emergency kit. If the first attempt fails, a replacement needle must be available for a new insertion at a different site.
• IO kits should be checked and restocked after every use and at regular scheduled intervals as part of emergency equipment maintenance.
• Dispose of used needles safely in a puncture-resistant sharps disposal container (sharps bin). Never recap a used IO needle by hand.
• Follow local or national biomedical waste disposal regulations for disposal of used IO needles and components.

IO vs IV: A Quick Comparison

Frequently Asked Questions (FAQ)

Suggested Further Reading and References