The Femoral Nerve Block is perhaps the easiest block to master if you are new to ultrasound or to I-Streme Echo. When starting in the world of ultrasound, this block is ideal because the landmarks you will be looking for are easy to find and you will rarely find yourself changing any settings on your device to see things better.
Indications: Anterior thigh, knee (ACL) surgery, hip procedures (read up on this new indication)
Landmarks: Inguinal crease
Local Anesthetic Volume: 20 mls
Level of Expertise: Beginner
Anatomy: Arising from L2, L3, and L4, this nerve is the largest of the lumbar plexus. As it enters the thigh it passes beneath the inguinal ligament, just lateral the the femoral artery which is easily seen with ultrasound. In the inguinal crease, you will often be able to often identify the fascia lata, fascia iliaca, and the ligament that separates the artery from the nerve.
View of the femoral nerve with a non-linear array ultrasound
Positioning: Patient is supine, both legs extended.
- I-Streme Echo
- Nerve stimulator (optional)
- 20 mls local anesthetic syringe
- 25 gauge needle for local infiltration
- Echogenic needle (optional)
- 15 MHz/5 cm setting (optional 24MHz/3cm setting)
- Start medial in the inguinal crease with the button on the probe facing you (lateral). Identify the Vein, lateral to it, the Artery, and lateral the the pumping vessel, the Nerve (VAN).
- Place the needle about 1 cm. lateral to the probe. (The more lateral you enter, the easier it will be for you to see the needle as it passes beneath the ultrasound.
- If you can't see the needle well, inject a tiny amount of anesthetic to identify the tip, rotate the probe clockwise or counter clockwise, and maybe move the probe to align it better with the needle's plane.
- If you are using a nerve stimulator, a visible patellar twitch at 0.5 mA would mean optimal placement of your needle tip.
- Aspirate every 5 mls and maintain a good view of the artery at all times. If you see bubbles inside it, you are probably intravascular!
- Watch for too much resistance when injecting - this could mean you are intra-neural. If so, move your needle out slightly and or reposition it.
- If you have a good view of the needle tip, inject the first 10 mls at the location where you were getting a patellar twitch at 0.5 mA. Then reposition your needle to an area where you see your local anesthetic has not spread well.
- Intravascular injection into the femoral artery.
- Nerve injury.