Ultrasound guided nerve blocksJo McDonnell

Femoral nerve block The femoral nerve block

provides anesthesia for the entire anterior thigh, the knee, and the femur.

In addition, skin anesthesia is conferred over the medial aspect of the distal lower extremity via the terminal branches of the femoral nerve.

Anatomy The lumbar plexus gives rise to the femoral

nerve (L2 – L4).  The femoral nerve enters the thigh passing

under the inguinal ligament, located lateral to the femoral artery surrounded by the fascia iliaca which separates it from the femoral artery and vein. 

Distal to the inguinal ligament, the femoral nerve splits into the anterior branch, providing skin sensation, and the posterior branches, supplying the quadriceps muscle, medial knee and skin sensation to the medial calf.

Femoral nerve block

Why use a probe? Ultrasound application allows

monitor the spread of local anesthetic and needle placement and make appropriate adjustments, should the initial spread be deemed inadequate.

because of the proximity to the femoral artery, ultrasound may reduce the risk of arterial puncture that often occurs with this block with the use of non-ultrasound techniques.

Palpating the femoral pulse as a landmark for the block is not required with ultrasound guidance, a process that can be challenging in obese patients.

A high frequency (6 – 18 MHz) linear array

A curvilinear probe can be used if more depth is warranted.

The probe is placed in the inguinal crease, in transverse.

The probe is slid until the femoral vessels are seen. The nerve lies about 1-2 cm lateral to the artery, positioned below fascia iliaca and lata and above the ilieopsoas muscle

The nerve itself can have a triangular or oval shape and is often not clearly visualized. Because of this, the triangle created by the femoral artery medially, fascial planes anteriorly and the iliopsoas muscle posteriorly is used as the target for the block. The nerve becomes visualized after injection.

Goal The goal is to place the needle tip

immediately adjacent to the lateral aspect of the femoral nerve, into the wedge-shaped tissue space lateral to the femoral artery.

Proper  deposition of local anesthetic is confirmed by observation of the femoral nerve being lifted off of the surface of the iliopsoas  or of the spread of the local anesthetic above in the wedged-shaped space lateral to the artery.

Median nerve block

Median nerve block toward the wrist deep to

the flexor digitorum superficialis in the center of the forearm.

superficial position until it is located beneath the flexor retinaculum in the carpal tunnel with the tendons of flexor digitorum profundus, flexor digitorum superficialis, and flexor pollicis longus

Median nerve-at the wrist

MN- at the wrist

MN-at the elbow In the antecubital fossa, the

median nerve lies medial to the brachial artery.

With the arm extended, a high-frequency (8-18 MHz) probe is placed tranversely over the brachial artery pulse.

Medial to the artery, the median nerve is exhibits its classic honeycomb appearance

Ankle block There are five nerves that provide

sensory innervation to the foot at or below the level of the ankle.  These are four distal branches of the sciatic nerve (posterior tibial, sural, deep and superficial peroneal nerves) and one branch from the femoral nerve (saphenous nerve).

Ankle block

5 nerves

2 deep Deep peroneal Posterior tibial

3 superficial Sup. Peroneal Sural Saphenous

5 nerves

2 deep Deep peroneal Posterior tibial

3 superficial Sup. Peroneal Sural Saphenous

Ankle nerve distribution

Ankle nerve distribution

Posterior tibial nerve

Groove behind the medial malleolus and achilles tendon

Locate posterior tibial artery

Nerve posterior to artery

Groove behind the medial malleolus and achilles tendon

Locate posterior tibial artery

Nerve posterior to artery

Superifical nerves

Blockade of all three superficial nerves is accomplished using a circumferential injection of local anesthetic subcutaneously

Level joint line to 5cm above joint

Blockade of all three superficial nerves is accomplished using a circumferential injection of local anesthetic subcutaneously

Level joint line to 5cm above joint

Complications Haematoma Failed block Intravascular injection infection

Contraindications Infection over injection site coagulopathy

Images obtained from www.nysora.com