Thumb through your local protocols and you will find that after you "zero in" on a differential diagnosis -- the work is not done, but rather, just beginning. A great deal of our patients will require invasive pharmacological interventions in the acute setting. Sometimes successful and timely completion of this task is easier said than done, especially in the back of a moving ambulance. Obtaining peripheral vascular access in an often chaotic and uncontrolled setting should be our bailiwick. However, some patients simply don't play nice or follow the rules. When things get difficult, it's comforting to know that we have more innovations in our arsenal than just IV catheters alone. Keep in mind, peripheral IV access doesn't just trouble EMS. Some research in 2007 (Lopostolle, Catineau, Garrigue, et al.) demonstrated that even in ideal environments, up to 10% of the time, IV access is not obtained in two attempts in the ED. Contributing factors could be vast and include patient characteristics like age, poor technique, physiologic stress found in setting of profound shock, just to name a few. That being said, IO access can be a great alternative and bridge to intravenous access. Additionally, training can be deployed rather quickly and in a safe manner. The good news continues as infection rates and complications are relatively low, and for short term use - this is a great resuscitation tool.
Intraosseous (IO) cannulation and accessing the medullary cavity of long bones has been in EMS for longer than you might think. In fact, IO access (manual) was heavily used during the second world war (WWII), eighty years ago. The beauty of its use and adoption across the world today (albeit assisted devices - multiple vendors) stems from the fact that your spongy medullary cavities are highly vascular and have excellent connections to systemic circulation. Consider these spaces to be like a vein that never collapses, even in states of shock, or critical illness/trauma (where no fractures exist) [see Figure 1].
Figure 1. Bone medullary space
Now where can they be placed?? As IO related research continues, so do the number of approved sites for IO cannulation. While many anatomical sites are available, most EMS agencies are beginning to lean towards these two preferred sites. They are finding that the targets are larger, the success rates are higher, and the landmarks are easier to find. For adults, consider the proximal humerus, and for pediatrics, consider the distal femur if feasible and your local protocols allow.
Proximal Humerus (large target for adults = reaches subclavian FAST)
(Aim just below the greater tubercle)
Distal Femur (large stable target for pediatrics)
(Aim above the articulation of the proximal tibia and patella)
PEARLS around IO access:
If patient is awake, consider slow/local anesthesia with lidocaine before saline flushes or medication administration. (This space doesn't flex)
You might not always be able to aspirate marrow in low flow states like VF arrest.
Flushing is paramount and "clears out" the medullary space.
Overcome intraosseous pressures with a pressure bag to achieve desired flow.
In normal circumstances, ideally replace after 24 hours.
These small details can make a huge difference in your success.
February 13, 2023
Author: Joshua Ishmael, MBA, MLS(ASCP)CM, NRP
Pass with PASS, LLC.