Continuous Femoral Nerve Catheter

Ultrasound Guided Femoral Nerve Block
Femoral nerve block provides analgesia for surgeries around the medial and anterior aspect of thigh and knee procedures. It can be used as anesthesia and analgesia for all lower limb surgeries when used in combination with Sciatic Nerve block.

Anatomy
Femoral Nerve is the largest nerve of the lumbar plexus and is formed by anterior primary rami L2, 3, 4. In the femoral triangle, at 1cm below the inguinal ligament, the femoral nerve lies 1 cm lateral to the femoral artery, deep to fascia iliaca and superficial to iliopsoas muscle. After 1-2 cm below the inguinal ligament, the femoral nerve divides into superficial branches and deep branches.

Patient positioning
Traditional position is to lay the patient supine with legs in neutral position. The groin and inguinal crease are exposed. In our hospital, the ultrasound machine is kept on the contra lateral side and facing towards the operator. This gives a good view and support for the operator.

Equipment
1. A high frequency probe (>10MHz)
2. 50-100mm short beveled needle
3.Nerve stimulator
4. Sterile preparation kit, syringes and local anaesthetic


Ultrasound scanning technique

After skin and probe preparation, start scanning the femoral triangle just below the inguinal ligament from medial to lateral. You can visualize the hypoechoic non-pulsatile femoral vein on the medial aspect and then the hypoechoic pulsatile femoral artery just lateral to femoral vein. Laterally, femoral nerve will be visualized in a triangular hyperechoic region, superficial to iliopsoas muscle. Femoral nerve is easy to locate below the inguinal ligament and is generally thin and flat in this area as it fans out into multiple branches.


Needling technique
In plane
After skin local anesthetic infiltration, insert a 5 cm 22G insulated block needle on the outer (lateral) end of the ultrasound probe and advance it along the long axis of the probe in the same plane as the ultra-sound beam. In this way, the needle shaft and tip can be visualized in real time at the time of needle advancement towards the femoral nerve.
Confirm the identity of the femoral nerve by electrical stimulation. Useful endpoint is patellar contraction classically called as “patellar dance”. Observe the pattern of local anesthetic spread below the fascia iliaca around the femoral nerve in real time during injection. In our hospital, we commonly use in plane approach for performing this block.

Out of plane
The femoral nerve is aligned with the midpoint of the transducer and the needle is inserted perpendicular to the probe. The tissue and needle movement is observed while advancing towards the nerve. While advancing the needle, inject 1-5 ml of D5W which will help to intensify the motor response to electrical stimulation. Moreover, injection of small amounts of D5W will expand the femoral triangle and the hypoechoic fluid collection can bring the hyperechoic nerve and the fascia iliaca into view. It can be technically challenging to track the location of the needle tip during needle insertion without an echogenic tip design. Move the needle tip slightly from side to side or in and out to bring the tip into view


Tips
1.Stimulation of the Sartorius muscle may mimic a quadriceps response but will lead to “block failure”, so make sure that the patella dances! If there is medial contraction (medial contraction), then retract the needle and angulate slightly to the lateral.
2.The inguinal lymph nodes may resemble the femoral nerve in cross section with a single level scan. It is therefore important to scan proximally and distally at the inguinal region and trace the course of the femoral nerve. In contrast, the inguinal lymph nodes are discrete superficial structures.
3.Aberrant femoral nerve location is not uncommon. So, it is important to scan proximal and distal to the inguinal region. The posterior division of the femoral nerve may be found above the iliopsoas muscle far lateral to the femoral artery.