US Guided Regional Anesthesia

2 – The anatomy of the femoral nerve

In the inguinal region the femoral nerve (FN) runs lateral to the femoral vessels and on top of the iliopsoas muscle

The femoral nerve runs below the iliacus fascia

To reach the nerve with your needle you have to penetrate two fascia: fascia lata and the iliacus fascia

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The femoral nerve is visible underneath the fascia lata and lateral to the femoral artery

1 – Anatomy of the femoral nerve

The lumbar part of the lumbosacral plexus emerges from five spinal nerves: T12, L1, L2, L3 and L4

It gives origin to three important nerves in lower limb innervation: The femoral, the obturator and the lateral femoral cutaneous nerves

The most important lumbar plexus nerve concerning basic peripheral nerve blockade is the femoral nerve

It originates from the L2, L3, and L4 spinal nerves of the lumbar plexus

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The figure shows the femoral nerve depicted with blue colour

5 – The muscles innervated by the femoral nerve

The femoral nerve splits into the anterior and the posterior branch

The femoral nerve innervates the muscles in the anterior compartment of the thigh

The anterior branch of the femoral nerve innervates the sartorius muscle – and sometimes the pectineus muscle

The posterior femoral nerve branch innervates most of the muscles in the anterior compartment of the thigh – i.e. the quadriceps femoris (the rectus femoris and the three vastus muscles)

Before the femoral nerve emerges from under the inguinal ligament it also innervates the iliac muscle and the femoral artery

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The quadriceps femoris muscle is innervated by the posterior femoral nerve branch. The quadriceps femoris muscle and the sartorius muscle are both depicted in turquoise colour. The sartorius muscle is innervated by the anterior femoral nerve branch.

3 – The anatomy of the femoral nerve

The femoral nerve runs below the iliacus fascia and on top of the iliacus muscle

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The figure shows the femoral nerve in cross section in green underneath the iliacus fascia. The femoral nerve is on top of the iliacus muscle (yellow asterix). Red profile = femoral artery. Blue profile = femoral vein. Cyan asterix = psoas major muscle tendon. Green asterix = pectineus muscle.

17 – Avoid injecting air perineurally

Before inserting the needle through the skin, the hose and the needle should be filled with saline or local anaesthetic

Just after insertion of the needle 1/2 ml of fluid should be flushed through the hose and needle to make sure that no air is contained in the “system”

Click on the VIDEO CLIP button to view the video

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The video shows the blurring effect of injected air during the performance of an infraclavicular nerve block
A = axillary artery; MaP = major pectoral muscle; MiP = minor pectoral muscle

13 – Infraclavicular block: Point of injection of local anaesthetic

In the infraclavicular block the local anaesthetic should be injected periarterially in the seven o’clock position (seeing the axillary artery as a clock face)

However, it is often necessary to reposition the needle tip in order to inject local anaesthetic periarterially from the two o’clock position around the artery to the ten o’clock position

Click on the VIDEO CLIP button to view the video

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Local anaesthetic is injected periarterially. lateral fascicle (LF); medial fascicle (MF); posterior fascicle (PF); axillary artery (A); local anaesthetic; (LA); minor pectoral muscle (MiP)

15 – Injection of local anaesthetic around the medial cord

The medial cord is located between the axillary artery and vein around the two o’clock position of the artery

The local anaesthetic does not always spread around the artery to the two o’clock position from a seven o’clock point of injection

In that case the needle tip should be repositioned in front of the axillary artery to the interspace between the axillary artery and vein and local anaesthetic should be injected periarterially

Click on the VIDEO CLIP button to view the video

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Periarterial injection of local anaesthetic between the axillary artery and vein in order to cover the medial cord of the brachial plexus
MaP = major pectoral muscle; MiP = minor pectoral muscle; A = axillary artery; V = axillary vein

14 – The infraclavicular block with repositioning of the needle tip

Repositioning of the needle tip is oftentimes necessary in order to cover all three cords around the axillary artery from two o’clock to ten o’clock

Care should be taken not to pierce the axillary vein

Click on the VIDEO CLIP button to view the video

In the video: Notice that local anaesthetic is injected on the wrong side of the clavipectoral fascia which has to be penetrated by the needle before local anaesthetic spreads appropriately around the medial cord

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The video shows repositioning of the needle tip during an infraclavicular block
First, local anaesthetic is injected around the lateral cord in the ten o’clock position
Then, the needle is relocated in front of the axillary artery in order to reach the medial cord

16 – Colour Doppler

Colour Doppler can be used to visualise the proxy marker – the axillary artery – and blood vessels that you do not want to perforate with the needle

It is also possible to use colour Doppler to visualise the injection of local anaesthetic

In that case it is an advantage to lower the PRF (Pulse Repetition Frequency) in order to enhance the visibility of the injectate

Click on the VIDEO CLIP button to view the video

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The video shows the pulsating colour Doppler signal from the axillary artery

9 – The intercostobrachial nerve

The brachial plexus innervates the entire upper limb – except part of the skin of the upper half of the medial arm which is innervated by the intercostobrachial nerve

The intercostobrachial nerve is synonymous to the lateral cutaneous branch of the second intercostal nerve

The intercostobrachial nerve joins the medial cutaneous nerve of the arm to supply the skin of the upper half of the medial arm

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The green colour depicts the intercostobrachial nerve which branches off as the lateral cutaneous nerve of the second intercostal nerve
The intercostobrachial nerve is not part of the brachial plexus