The Femoral Nerve Block
Michael Macias
By John Sarwark; Edited by Michael Macias
Hey Clubhouse! Sorry we've been out of the loop lately. We all just flew back in from San Diego, and boy are our arms tired.
One of our beloved colleagues from the community has recently declared to us his love of ultrasound guided nerve blocks--a skill that is established in the anesthesia world but is quickly gaining traction in our realm. Some programs are training their residents in this skill, and some aren't. But we've been inspired to talk about it! That said we will now be featuring a series of posts on this very subject. Our inaugural post today: femoral nerve blocks.
The Case
Let's say we do a little time warp, and we are unfortunately six months into the past, stuck in the dredges of frigid winter. EMS appears with a patient who just wiped out big time on the ice. He's gripping his thigh with his hands, and he is screaming. Maybe he's broken his hip? Maybe it's dislocated? Maybe he cracked the shaft of his femur? For this exercise, let's say that it doesn't matter.
What does matter is that it looks like this might need a little pushing and pulling, either to get it reduced or maybe just for re-positioning for imaging. Procedural sedation? I mean, we're always down for that, but is there a better way?
Turns out there is! Specifically we will discuss the femoral 3-in-1 block--so titled as it knocks out the lateral cutaneous, obturator, and femoral nerves. This will completely anesthetize the femoral shaft, with some coverage of the proximal end of the femur. This can be done blind, but adding U/S greatly increases the chance of success--the evidence that's out there has shown that using a probe gets you blockade faster and has a higher rate of complete blockade.
How it's done
You'll need the following for your setup:
- U/S machine with a linear probe
- 21 G spinal needle with attached syringe
- Vial of 0.5% bupivacaine or 1% lidocaine
- Sterile gloves
- A sterile probe cover
- Sterile gel
Essentially your goal is to infiltrate the area inferior to the fascia illiaca, allowing for the rapid distribution of anesthetic to the above mentioned nerves. And to properly do this procedure, you'll need a LOT of local anesthetic--our sources recommend up to 30 mL of bupivacaine or lidocaine, depending on how long a duration of anesthesia you are attempting to achieve.
When done blind, to confirm you'll either feel a gratifying "pop", your patient will get a paresthesia, or you will feel the pulsations of the femoral artery pushing your needle laterally. But we can do it better! For this jobby, prep and drape the area. Place your probe per convention in the transverse plane, starting at the inguinal ligament. Slide down until you can see the femoral vein and artery (about 2 cm caudad). You shouldn't miss these guys. Just lateral to them is the femoral nerve, which appears as a hyperechoic triangular structure. Review the images below for anatomy of interest:
Click on images above to enlarge
After you are comfortable with your anatomy, make a wheal for entry just lateral to the probe. Identify the triangle shaped femoral nerve, lateral to the femoral artery, as well as the iliopsoas muscle and the fascia illiaca running over its surface. The nerves run under this fascia so your goal will be to guide your needle into that space. Now advance your spinal needle directed medially at a 30 degree angle. Get your tip as close as possible to the nerve, and under the fascia illiaca, then inject (well, after aspirating first, of course). You should see the local anesthetic spread the fascia away from the muscle tissues in a cephalad direction. You'll want to hold pressure distally during all of this, and then 5 minutes after injection.
Here's a fantastic demonstration from the fine people at SonoSite:
Here's the usual video (with the usual unconventional hilarity) from Whit Fisher. It's a bit of a departure from what we've described above--he mainly goes right at a shaft fracture--but it's the same general idea:
As always, these posts are for EDUCATIONAL PURPOSES ONLY. These nerve blocks have the potential to be huge for us as emergentologists, but don't take our word for it. Sure, it feels good to be a trailblazer, but it definitely doesn't feel good to be a lawsuit prone bumbler. Do your research, and always be safe.
jps
Sources
- Roberts and Hedges Clinical Procedures in Emergency Medicine. Saunders 2014, Chapter 31
- Beaudoin, F. L., Haran, J. P., & Liebmann, O. (2013). A Comparison of Ultrasound-guided Three-in-one Femoral Nerve Block Versus Parenteral Opioids Alone for Analgesia in Emergency Department Patients With Hip Fractures: A Randomized Controlled Trial. Academic Emergency Medicine, 20(6), 584–591. doi:10.1111/acem.12154
- Cristos, S., Chiampas, G, Offman, R, & Rifenburg, R. (2010). Ultrasound-Guided Three-In-One Nerve Block for Femur Fractures. Western Journal of Emergency Medicine. 11(4), 310-313
- Turner, A. L., Stevenson, M. D., & Cross, K. P. (2014). Impact of ultrasound-guided femoral nerve blocks in the pediatric emergency department. Pediatric Emergency Care,30(4), 227–229.
- Reid, N., Stella, J., Ryan, M., & Ragg, M. (2009). Use of ultrasound to facilitate accurate femoral nerve block in the emergency department. Emergency Medicine Australasia,21(2), 124–130. doi:10.1111/j.1742-6723.2009.01163.xdoi:10.1097/PEC.0000000000000101
- Fletcher, A. K., Rigby, A. S., & Heyes, F. L. P. (2003). Three-in-one femoral nerve block as analgesia for fractured neck of femur in the emergency department: A randomized, controlled trial. Annals of Emergency Medicine, 41(2), 227–233. doi:10.1067/mem.2003.51
- SonoSite YouTube Page
- Whit Fisher's YouTube Page