In parts 1 and 2 of this series, we have outlined the indications, contraindications, medications that can be infused through and IO, needle size selection and driver characteristics. Now lets unpack how to landmark for EZ-IO insertion. As stated in Part 2, the ends of long bones contain a large amount of red blood cells (RBC) and therefore allow for better performance as it pertains to medication infusion.
The proximal humerus is the preferred site due to the fact that average flow rates are approximately 6.3 liters per hour and above while the proximal tibia has a much lower average infusion rate. Medication delivery to the central circulation (right atrium) is less than 3 seconds with a properly placed proximal humerus IO while the proximal tibia, while still an acceptable site, offers a much slower overall central circulation delivery time. Additionally the proximal humerus has been shown to have less infusion related pain compared to the proximal tibia. To date there have been no reports of compartment syndrome with the proximal humerus insertion site.
Landmarking for the proximal humerus involves placing the arm against the body, or adducted, and the hand over the abdomen or placing the elbow against the body with the arm straight down and rotating the palm out and thumb down. Both of these maneuvers internally rotate the bicep brachii tendon internally and therefore make it much less likely to damaged during insertion. The most prominent portion to the greater tubercle is the ideal insertion site for the proximal humerus. Typically in the adult patient who weighs greater than 40 kgs (88 pounds) the yellow 45 mm needle is preferred and is inserted at a 45 degree angle as if aiming towards the patient’s opposite hip. Proximal tibia insertion landmarking involves measuring 3 cm distal to the bottom of the patella and then from there go 1-2 cm medially and feel for the “flat spot or divot”. This is the tibial plateau and the optimal site for proximal tibia insertion. Because most adult patients have less overlying tissue in this area, the blue 25 mm needle is often utilized in the proximal tibia and the insertion angle is perpendicular to the flat bone surface. Distal tibia, while used very infrequently is an additional potential IO insertion option. It can be landmarked by measuring approximately 3 cm up from the medial malleolus and then identifying the anterior and posterior borders of the distal tibia. The insertion site will be between these two borders. As in the proximal tibia, most adult insertions at this site will be done using the blue 25 mm needle set. Distal Femur insertion site utilization is indicated for patients under 21 years of age and will be discussed in future installments of this series.
Insertion is a tow step process regardless of the anatomic insertion site. After landmarking and cleaning the site, insert the appropriate sized needle through the skin while it is attached to the driver until you can feel the needle contact the bone. Look down at the needle to ensure that you can still see at least one black line. If at least one black line is seen on the needle at this point, the needle will be long enough to successfully enter the inter medullary space. If at least one black line cannot be seen, the needle is not long enough and either a longer needle must be used or an insertion site with less overlying tissue must be used. Step two of the insertion process involves activating the driver and applying gentle, consistent downward pressure on the driver and letting the driver and the patented needle set pierce the cortical bone. Insertion should be stopped once a palpable release of pressure or dropping in of the needle into the inter medullary space is felt. After insertion, the needle should feel as if it is firmly seated in the bone with little movement and the internal stylet can be removed. An EZ-IO stabilizer should be placed at this point if available. Attach the pre primed extension set and optional attempts at drawing back on the attached pre filled syringe may be performed to further confirm proper IO placement in the inter medullary space. It should be noted that inability to obtain either blood or bone marrow in the extension set hub while drawing back the syringe is not necessarily a confirmation of a failed placement. Rapid flushing of the EZ IO is now performed with 5-10 ml of NS and do not be surprised if there is some resistance initially when flushing until the inter medullary pathway or pocket is established. Infusion related pain is directly related to both the rate and the anatomic insertion site and will be discussed in future installments.
After successful insertion of an EZ-IO needle, the patency of the device must be ensured before every use. Look for signs and symptoms of infiltration both around the insertion site and posteriorly. A rapid flush of 5-10 ml of isotonic crystalloid solution will aid in re establishing the medication infusion route in the inter medullary space. Ideally, infusing a slow infusion of non medicated fluids will assist with maintaining IO patency after insertion. The proximal humerus insertion site must be protected from accidental dislodgment by securing the arm against the chest as abduction of the elbow can result in accidental dislodgment. Standard automatic CPR devices can be used safely with the proximal humerus IO in place.
As stated earlier, IO insertion is no longer just for the critical patient that has had multiple unsuccessful IV insertion attempts performed. It can be a reliable, rapid and effective route for medication and fluid administration in the patient that is urgent, emergent or medically necessary. While it is not meant to replace intravenous insertion, it can be another option for the patient that requires vascular access regardless of perfusion status.
