Ultrasound-guided femoral nerve block is preferred over the landmark technique because it has the benefits of direct visual¬ization of the relevant anatomical structures, real-time control of needle advancement and a reduced number of needling attempts, assessment of the spread of anesthetic around the nerve, decreased amounts of anesthetic required to achieve a nerve block and fewer complications (e.g., intravascular or intraneural injection, local anesthetic systemic toxicity).

1. KidSONO Femoral Nerve Block text, Why Ultrasound Section
2. Marhofer P, Greher M, Kapral S. Ultrasound guidance in regional anaesthesia. Br J Anaesth. 2005 Jan;94(1):7-17. Epub 2004 Jul 26. Review. PubMed PMID: 15277302.

A: Indications for femoral nerve block include acutely painful conditions affecting the femur, patella and anterior thigh.

1. KidSONO Femoral Nerve Block text, Indications Section

A: Contraindications to femoral nerve block include patient refusal, infection over the injection site, and allergy to local anesthetic. Anticoagulation is a relative contraindication.

1. KidSONO Femoral Nerve Block text, Contraindications section

A: Complications of femoral nerve block include: block failure, infection, intraneuronal injectiong and intravascular injection. Complications are less likely under ultrasound-guidance compared to the traditional landmark approach.

1. KidSONO Femoral Nerve Block text, Complications section

A: The femoral triangle is bordered by the inguinal ligament superiorly, the sartorius muscle laterally and the adductor longus muscle medially.

1. KidSONO Femoral Nerve Block module, Anatomy Review section

A–Fascia Lata

B–Femoral vein

C–Femoral Artery

D–Femoral Nerve

E–Fascia Iliaca

F–Pectineus

G—Iliopsoas

1. KidSONO Femoral Nerve Block text, What am I looking at section

The femoral artery lies medial to the femoral nerve and lateral to the femoral vein, it is deep to the hyperechoic fascia lata and superficial to hypoechoic iliopsoas muscle. It has a circular structure with thick muscular walls which do not compress easily with pressure from the transducer. When color mode is used the pulsatile flow of arterial blood can be visualized.

1. KidSONO Femoral Nerve Block text, What am I looking at section

The femoral nerve has a hyperechoic, “honeycomb” appearance in cross section on ultrasound. It’s shape can vary from circular, to flat or even triangular.

1. KidSONO Femoral Nerve Block text, What am I looking at section

Within a few centimeters of the inguinal ligament, the femoral nerve divides into anterior and posterior branches. It is important to place your blockade around the nerve prior to when it diverges, otherwise your block may be incomplete. If you are too distal, you may miss the posterior branch of the femoral nerve which provides motor innervation to the quadriceps muscles–an important consideration in patients with acute femur fractures who are experiencing quadriceps spasm.

1. KidSONO Femoral Nerve Block text, anatomy review and technique sections
2. Tondare AS, Nadkarni AV. Femoral nerve block for fractured shaft of femur. Can Anaesth Soc J. 1982 May;29(3):270-1. PubMed PMID: 7074406.

Prior to beginning the procedure ensure the patient is lying supine with the affected leg slightly abducted and externally rotated in order to expose the inguinal crease.

1. KidSONO Femoral Nerve Block text, Technique section

Ensure that the ultrasound machine is easily in view, ideally inline, as you approach the patient so that you can see both the needle and the screen as you proceed. The high-frequency linear transducer is placed transversely along the inguinal crease with the probe marker towards the patient’s right.

1. KidSONO Femoral Nerve Block text, Technique section

The maximum dose of bupivacaine is 2.5mg/kg. In a 15kg child, this would be:
2.5mg x 15kg = 37.5mg

1. KidSONO Femoral Nerve Block text, Technique section

The maximum dose of bupivacaine is 2.5mg/kg. In a 15kg child, this would be:
2.5mg x 15kg = 37.5mg

0.25% Bupivicaine contains 2.5mg/mL of Bupivicaine, therefore:
37.5mg / 2.5mg/mL = 15mL

1. KidSONO Femoral Nerve Block text, Technique section

To enhance visualization of the needle on ultrasound first, one can use an echogenic needle or needle visualization preset on the ultrasound machine. In addition, one can sweep or rotate the probe to ensure the ultrasound beam is directly in line with the needle. Finally, one can attempt to improve needle visualization through the use of hydro-localization.

1. KidSONO Femoral Nerve Block text, Technique section

While both techniques may be used, there is some evidence that injection of local anesthetic anterior to the femoral nerve but deep to the fascia iliaca results in fewer needle redirections and improved cutaneous analgesia when compared to posterior injections.

1. KidSONO Femoral Nerve Block text, Technique section
2. Szűcs S, Morau D, Sultan SF, Iohom G, Shorten G. A comparison of three techniques (local anesthetic deposited circumferential to vs. above vs. below the nerve) for ultrasound guided femoral nerve block. BMC Anesthesiol. 2014 Jan 25;14:6. PubMed PMID: 24460975.