Intraosseous (IO) infusion

Just a quick rundown on the intraosseous (IO) lines that we’d better get more familiar with as we enter residency.  Especially during traumas or codes, the intraosseous line is invaluable in securing access in a volume depleted pt or small child.  IO lines infiltrate the spongy, cancellous bone that’s inside of the hard, outer compact bone.  Ideal locations are those with large networks of vascular, trabecular meshwork of red bone marrow.  These sites are at the end of long bones (femur, humerus, tibia, and sternum) where the intraosseous vasculature drains quickly into the central venous canal and central circulation.

In addition to the conventional uses of IO lines, I thought it’d be interesting to wrap up this post with a couple articles/case reports that further showcase the utility of IO infusion.  It has potential as a means for invasive systemic blood pressure monitoring and for hastening the delivery of vasoactive drugs especially in the setting of out of hospital cardiac arrest.  These articles will be at the end.

What is it?  When is it indicated?

Per Wikipedia, the IO infusion is the process of injecting directly into the bone marrow to provide a non-collapsible (2/2 the hard cortex keeping things patent) entry point into the systemic vasculature.  What this means for us: IV blown or can’t be attained?  US currently being used for FAST?  Grab the IO kit.  In short, American Heart Association guidelines recommend IO infusion if IV cannot readily be obtained.  Don’t perform IO infusion when there’s overlying infection, high risk of fracture or IVC injury (drugs/fluids will extravasate).

For historical perspective, the IO route was first mentioned in the 1920’s literature when the sternum was suggested as a site for potential blood transfusion.  During WWII, IO infusion was used; however, subsequent popularity of the plastic catheter overshadowed the adoption of IO until the 1970’s.

In general, the IO kit contains a driver and needle tips.  The FDA has approved three devices for adult trauma pts in whom IV access cannot be obtained.  The pictures (largely from the Critical Care Nurse article) are below, but the one I’ve seen most in the hospital are the EZ-IO (for proximal and distal tibia as well as proximal humerus).  The two others are FAST 1 (for sternum) and Bone Injection Gun (proximal tibia and proximal humerus).  There’s a couple pics of the FAST 1 and Bone Injection Gun, but we’ll focus on the EZ-IO.

Finally, in terms of pain, the IO method doesn’t seem to be as horrible as it may first look.  On a scale of 1-10, an observational study found an average of  a 3.9 rating for insertion with a removal score of 2.2.  Doesn’t seem to be too bad, but I don’t think I’ll try it on myself yet…

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What are the risks?  

As the benefits are fairly obvious when thinking intuitively about the whole thing, the risks of IO infusion should not be overlooked.

Compartment syndrome – Can occur when IO improperly placed and there’s extravasation of fluid into surrounding tissue space.  Specifically, there is risk of IO needle passing through both sides of bone cortex and infiltrating soft tissue space.  Prevent this by removing improperly placed IO needle when does not flush cleanly.  Can also confirm proper placement by aspirating bone marrow.

Infection/osteomyelitis – An intuitive risk of IO infusion since we’re creating a pathway from outside to inside.  More often due to poor aseptic technique or leaving the IO in for longer than 24 hrs.  The goal is generally to leave the IO in for no longer than 3-4 hrs.

Extravasation – Specific to more dangerous fluids, the extravasation of caustics/hypertonics like sodium bicarb, dopamine or calcium chloride can cause muscle necrosis.

How do you do it?

The proximal tibia is the site I’ve seen most commonly in my few years in the hospital.  Its flat surface, easily identifiable landmarks and distance from the thorax (where resus attempts are happening) make it ideal.  Grab driver; put on needle tip; aim slightly medial and 2 cm distal to tibial tuberosity; push hard (lidocaine prior to this if pt awake).  Passage through cortex and infiltration of the marrow space  will be identified by sudden drop in resistance or pop feeling.

For distal tibia, aim slightly proximal to the medial malleolus.  Drill into flat portion of tibia here.  Make sure to angle 15 degrees cephalad to avoid growth plate.

For proximal humerus, drill 90 degrees directly into the greater tuberosity.

Confirm proper placement via infusion of fluid without extravasation to surrounding area.  Make sure to flush line adequately upon insertion; a decently forceful infusion helps push away the bone spicules in the bony medulla.  If there’s a need for fast fluid administration, pressure bags, 60 cc boluses and IV pumps can be used.

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IO as invasive blood pressure monitors

Now, for the recent developments on IO infusion…

A recent article in the American Journal of Emergency Medicine published a case report that supports the ability of intraosseous pressure (IOP) to consistently reflect systemic blood pressure.  Prior to this, animal studies had shown the parallel relationship between intraosseous and intravenous environments.  The correlation between IO and IV readings for blood pressure and arterial waveform (yes, even despite the IO reading being venous and the IV being arterial) have sparked some thoughts on the structural relationship and the future potential for monitoring that IO may possess.  The thought is that since there’s similarities between the structure of intraosseous vasculature and the overlying venous vasculature there may be some therapeutic potential by studying the two.

“Intraosseous arterioles are similar histologically to arterioles located throughout the body, and include an intima, media and an adventitia. This suggests intraosseous arterioles regulate blood flow in a similar manner to arterioles located in other anatomic locations.”

IO infusion vs. IV infusion for vasoactive drugs

Relevant considerations when comparing IO vs. IV access are the different pharmacodynamics of the two methods.  Specific to pressors in cardiac arrest, studies have looked at the differences between IO and IV.  At the heart of the discussion is the unquestionable speed with which IO can be placed.  On the other hand, the utility of expeditious placement is offset by the delay that IO infusion has in achieving peak drug levels along with generally diminished absorption (which also varies amongst IO sites like tibia vs. sternum).  A recent article in Resuscitation brought up additional interesting discussion points specific to IO access in out of hospital cardiac arrests.  “Lastly, it is worth noting that the optimal pharmacodynamic approach to intra-arrest medication administration remains unclear, both experimentally and clinically. Whether achieving high peak levels is preferable over strategies in which a lower drug concentration is sustained over a longer period of time is not known. It is also possible that the delay to peak concentration and lower absorption associated with tibial IO administration of medications can be overcome by higher doses.”  If IO is going to become more readily utilized, there are many more discussions to be had on resuscitation protocol.

References

Day MW. Intraosseous devices for intravascular access in adult trauma patients. Critical Care Nurse. 2011;31:76-90.

Gluckman W, Forti R, Lamba S. (2012, Jun 13). Intraosseous cannulation. Emedicine. Retrieved 03/07/14 from http://emedicine.medscape.com/article/908610-overview#aw2aab6b6.

Frascone RJ, et al. Use of an intraosseous device for invasive pressure monitoring in the ED. Am J Emerg Med. 2014. http://dx.doi.org/10.1016/j.ajem.2013.12.029.

Davis DP. The use of intraosseous devices in cardiopulmonary resuscitation: is this the answer for which we have been searching? Resuscitation. 2012;83(1):7-8.

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