Confirming intraosseous (IO) placement relies on a combination of physical signs: the needle should stand firmly in the bone without support, a saline flush should flow freely without swelling around the site, and you may be able to aspirate bone marrow. No single sign is definitive on its own, so you check several indicators together to build confidence that the needle is seated correctly in the marrow cavity.
The Core Confirmation Signs
There are three primary checks, and they should be performed in sequence after insertion.
- Needle stability. A properly seated IO needle will stand upright on its own, held in place by the cortex of the bone. If the needle wobbles, leans, or can be easily displaced, it may not have penetrated fully into the marrow space.
- Bone marrow aspiration. Attach a syringe and attempt to draw back. Successful aspiration of blood or marrow is a strong positive sign. However, failure to aspirate does not necessarily mean the needle is misplaced. In a German surveillance study of 169 successful pediatric IO insertions, bone marrow aspiration was only achieved in about 54% of cases. If you can’t aspirate on the first try, flush with a small amount of saline and attempt aspiration again.
- Saline flush without extravasation. Flush 10 mL of normal saline through the line. The flush should flow smoothly with minimal resistance. Watch the tissue around the insertion site closely for any swelling, firmness, or puffiness. If fluid is leaking into the surrounding soft tissue instead of entering the vascular space, the needle is either misplaced or has penetrated through the far side of the bone.
During insertion itself, you should feel a distinct loss of resistance as the needle passes through the hard outer cortex and enters the softer marrow cavity. That tactile “pop” or “give” is the first clue that you’ve reached the right depth, even before you begin your formal confirmation checks.
What Extravasation Looks Like
Extravasation, where fluid leaks into the tissue surrounding the needle, is the clearest sign of a misplaced or failed IO. During and after your saline flush, inspect the area around the insertion site and check the opposite side of the limb as well. Fluid can track behind the bone and pool where you wouldn’t immediately see it.
Early signs include local swelling and skin tightness around the insertion point. As severity increases, you may see redness, discoloration, blistering, or skin that feels cool to the touch. In the same pediatric surveillance study, about 77.5% of successful first-attempt insertions showed no signs of extravasation, meaning that roughly one in four attempts did show some degree of fluid leaking into tissue, reinforcing why careful monitoring matters even after initial placement seems successful.
If you see swelling develop during or after the flush, stop the infusion. The needle needs to be removed, and a new attempt should be made at a different site, ideally on a different limb entirely.
Site-Specific Considerations
Proximal Tibia
This is the most common IO site in both adults and children. The landmark is the flat, broad surface just below the knee on the inner (medial) side of the shinbone. After insertion, the same three-step confirmation applies: stability, aspiration attempt, and flush. Because the tibia has relatively thin soft tissue over it, extravasation is usually easy to spot visually.
Proximal Humerus
The upper arm site is increasingly used in adult resuscitation because it allows faster flow rates and drug delivery to the central circulation. Proper arm positioning is critical: place the patient’s hand over their belly button with the elbow bent and the arm tucked against the body. This rotates the insertion site into the correct position and protects the biceps tendon.
For patients over 40 kg, a longer 45 mm needle is required. A shorter 25 mm needle fails to reach the marrow cavity in up to 50% of adult patients at this site. After insertion, check that at least one black line on the needle (representing 5 mm) is still visible above the skin. If the needle is buried to the hub, it may have gone too deep. Flush with 10 mL of saline and watch for swelling in the shoulder or upper arm. Aspiration of marrow is not required to confirm placement at this site.
Distal Femur
This site is used primarily in infants and young children. The landmark is the flat area just above the kneecap on the midline of the thigh bone. Because pediatric bones are softer, the loss-of-resistance sensation during insertion can be more subtle. The confirmation steps remain the same, but pay particular attention to the flush, as the thigh has more soft tissue that could mask early signs of extravasation.
Ultrasound as a Backup Check
Point-of-care ultrasound can add an extra layer of confirmation when you’re uncertain. There are two main techniques. The first uses a special ultrasound mode (power Doppler) placed over the bone near the insertion site to detect fluid flowing through the marrow space. A small cadaver study found this method was 100% sensitive and specific, though a larger animal study showed more modest results: 72% sensitivity and 79% specificity. The second approach uses ultrasound to look for fluid accumulating in the soft tissue around the needle, which would indicate extravasation. This technique has been shown to be about 94% accurate.
Ultrasound is most useful when clinical signs are ambiguous, such as when you can’t aspirate marrow and the flush feels slightly more resistant than expected but there’s no obvious swelling. It’s a supplement to the physical checks, not a replacement.
Troubleshooting a Questionable Placement
If the needle feels stable but you can’t aspirate marrow, don’t automatically assume failure. Flush 5 to 10 mL of saline through the line, then try aspirating again. The initial flush can clear clotted marrow from the needle tip and allow aspiration on the second attempt. As long as the flush flows freely and there’s no swelling at the site, the line is likely functional.
If the flush meets significant resistance, pause and reassess. High resistance can mean the needle tip is pressed against the far cortex of the bone, the needle hasn’t fully entered the marrow cavity, or the lumen is clogged. Slight repositioning or withdrawing the needle a millimeter or two (without pulling it out of the bone) can sometimes resolve cortex contact. If the problem persists, remove the needle and reattempt at a different site.
A needle that starts infusing well but later develops increasing resistance or new swelling around the site may have shifted. This is why proper stabilization after confirmed placement matters. Most IO device kits include stabilization dressings or supports designed for this purpose. Avoid placing tension on the tubing connected to the line, and monitor the site continuously during use.