UGRAbas

3 – Anatomy of the ilioinguinal nerve

The ilioinguinal nerve (IIN) typically emerges together with the iliohypogastric (IH) nerve from the lateral margin of the psoas major, descends laterally across the anterior side of the quadratus lumborum, pierces the posterior aponeurotic extension of the transversus abdominis, and runs medially together with the IH nerve sandwiched between the transversus abdominis and the internal oblique – first on top of the iliac crest, and then on top of the inguinal ligament

The IIN exits via the external inguinal ring and terminates as the anterior scrotal/labial branches

Together with the IH nerve the IIN innervates the inferior portions of the transversus abdominis and the internal oblique

The anterior scrotal branches innervate the skin proximal to the symphysis and the lateral parts of the male scrotum and the female labia majora

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Ilioinguinal nerve (IIN, magenta), anterior scrotal branches (red arrow), IIN runs between the transversus abdominis and internal oblique on top of both the iliac crest and the inguinal ligament (blue and green arrows). Quadratus lumborum, transversus abdominis, psoas major, and iliacus (yellow, magenta, cyan & green asterixs).

4 – Scanning technique with the ultrasound guided ilioinguinal/iliohypogastric nerve block

– Place the patient supine

– Identify the anterior superior iliac spine (ASIS) with palpation and ultrasound

– Place the high-frequency linear probe on the line connecting the ASIS and the umbilicus and with the lateral end of the probe just superior to the ASIS

– Identify the layers of the abdominal wall and the iliohypogastric and ilioinguinal nerves and the deep circumflex artery inside the neurovascular fascial plane between the transverse abdominis and the internal abdominal oblique (see next page)

– Insert the needle with in-plane technique from the lateral end of the probe and advance the needle tip to the neurovascular plane. Inject 15 mL of local anaesthetic

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In-plane approach to block the ilioinguinal/iliohypogastric nerves with ultrasound guidance
Ca = caudad, cr = cranial

5 – Sonoanatomy of the ilioinguinal/iliohypogastric nerve block

Local anaesthetic is injected into the fascial plane between the transverse abdominis and the internal oblique muscles

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Iliohypogastric nerve (cyan arrow), ilioinguinal (red arrow), transverse abdominis (cyan asterix), internal abdominal oblique (magenta asterix), external abdominal oblique (yellow asterix), anterior superior iliac spine (ASIS, blue asterix), needle (long red)

6 – Supraclavicular anatomy

The brachial plexus runs across the first rib in close relationship to the subclavian artery

On top of the first rib the branches of the brachial plexus are located postero-superior to the artery

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The subclavian artery (green arrow) ends at the lateral margin of the first rib (blue arrow) where it becomes the axillary artery which dives under the clavicle (magenta arrow)

7 – Supraclavicular approach: the brachial plexus is a cluster of black profiles

Align the pulsatile subclavian artery to the center of the monitor

Rotate and tilt the transducer to obtain the best possible SAX view of the pulsatile subclavian artery and brachial plexus nerve divisions

Adjust depth, gain and focus

The hyperechoic first rib has to be exactly underneath the vessel. The pleura is posterior to the first rib. (Note air artifact, periodic

9 – Always place the probe on top of the first rib and you will see the pleura

It is important to locate the probe on top of the first rib

With in-plane needle approach the needle tip will impinge on the rib instead of producing a pneumothorax, if the needle is inserted too deep

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The movie shows the typical sonographic image when the probe is placed on top of the first rib
P = pleura, c1 = first rib, SA = subclavian artery, asterixs = nerve divisions of the brachial plexus. Post = posterior, ant = anterior

10 – Always inject local anesthetic in the corner pocket

Local anesthetic has to be injected in the angle between the subclavian artery, the first rib and the bundle of nerve divisions

SA = subclavian artery

nd = bundle of nerve divisions

p = pleura

c1 = first rib

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The video shows how the needle (asterixes) is inserted with in-plane technique and advanced underneath the bundle of nerve divisions (nd) of the brachial plexus in order to inject local anesthetic in the corner pocket. SA = subclavian artery, c1 = first costa, p = pleura.

8 – The corner pocket

The lowermost branches of the brachial plexus – originating from the C8 and T1 spinal nerve roots – run across the first rib in the corner between the rib and the subclavian artery

This is called the corner pocket

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The lowermost branches of the brachial plexus run across the first rib in the corner pocket

11 – Always insert the needle with in-plane technique

It is mandatory to insert the needle with in-plane technique for the supraclavicular brachial plexus block in order to minimize the risk of pneumothorax

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The needle is inserted with in-plane technique. The fascicular profiles (black profiles) are meticulously avoided by the needle tip. The needle is advanced under the neural epineurium. SA = subclavian artery, asterixs = divisions of the brachial plexus, LA = local anesthetic.

5 – How to place the probe for the supraclavicular block

– Position the patient supine with the head turned contralateral

– Align the anatomical target and the monitor in the same visual field

– Select a linear, high-frequency probe 15-10 MHz

– Place the probe is in the supraclavicular fossa in the coronal oblique plane

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The probe is oriented antero-posterior in the parasagittal plane on top of the first rib