Yeditepe University Faculty of Medicine 1st Year Anatomy ...



NERVE BLOCKS

21.March.2012 Thursday

CLINICAL ANATOMY OF THE BRACHIAL PLEXUS BLOCK

In the neck, the brachial plexus occupies the lower part of the posterior triangle. It lies below and anterior to a line connecting the cricoid cartilage of the larynx to the midpoint of the clavicle. In the axilla, the

brachial plexus and its branches are arranged within the axillary sheath around the axillary artery, which can be

palpated.

Injection of an anesthetic solution into or immediately surrounding the axillary sheath interrupts conduction of impulses of peripheral nerves and produces anesthesia of the structures supplied by the branches of the cords of the plexus. Because the axillary sheath encloses the axillary vessels and the brachial plexus, a brachial plexus nerve block can easily be obtained. The distal part of the sheath is closed with finger pressure, and a syringe needle is inserted into the proximal part of the sheath. Sensation is blocked in all deep structures of the upper limb and the skin distal to the middle of the arm.

The brachial plexus can be anesthetized using a number of approaches, including an interscalene, supraclavicular, infraclavicular and axillary approach or block.

Interscalene Block

Procedure: With the head turned laterally and upward from the side of the block, the palpating finger can feel the groove between the scalenus anterior and the scalenus medius muscles just lateral to the sternocleidomastoid muscle. The blocking needle is inserted into the interval between the scalene muscles, and the roots of the upper part of the brachial plexus can be blocked.

Supraclavicular Block

Procedure: The trunks of the brachial plexus can be blocked as they cross the first rib and enter the axilla. A blocking needle is inserted between the scalenus anterior and the scalenus medius muscles and

directed caudally behind the subclavian artery toward the upper surface of the first rib. It is here that the brachial plexus is very compact, consisting of the upper middle and lower trunks.

Infraclavicular Block

Procedure: The middle of the clavicle is identified. A blocking needle is inserted 1 in. (2.5 cm) inferior to it.

Anatomy of complications: The close relationship of the axillary vessels to the brachial plexus within the axillary sheath means that vessel puncture and hematoma formation may occur.

Axillary Block

Procedure: With the arm abducted to an angle greater than 90°, the axillary artery within the axillary sheath

may be palpated high up in the axilla. The artery is compressed, and a blocking needle is inserted just proximal to the point of compression into the axillary sheath. The disadvantage of this approach is the difficulty in blocking the musculocutaneous nerve. The object of compressing the artery distal to the point of injection is to close off the axillary sheath distally so that the anesthetic agent may rise in the sheath to the musculocutaneous nerve.

Anatomy of complications: The close relationship of the axillary vessels to the brachial plexus within the axillary sheath means that vessel puncture and hematoma formation may occur.

Musculocutaneous Nerve Block

Indications: Repair of lacerations on the lateral border of the forearm

Procedure: These include the following:

Brachial plexus approach: The musculocutaneous nerve trunk may be blocked with the rest of the brachial

plexus. The infraclavicular or axillary approach is used; in the axillary approach great care has to be taken to ensure that the anesthetic agent rises sufficiently high in the axillary sheath to block the musculocutaneous nerve.

Lateral cutaneous nerve of the forearm approach: The musculocutaneous nerve may also be blocked as it

emerges between the biceps and the brachialis muscles just above the lateral epicondyle of the humerus, where

it becomes the lateral cutaneous nerve of the forearm. The needle is inserted just lateral to the tendon of the biceps muscle on a line between the two epicondyles of the humerus.

Median Nerve Block

Area of anesthesia: The skin on the lateral half of the palm, the palmar aspect of the lateral three and a half

fingers, including the nail beds on the dorsum.

Indications: Repair of lacerations of the palm and fingers

Procedures: These include the following:

Block at the elbow: With the elbow joint extended, the brachial artery can easily be palpated in the cubital fossa on the medial side of the tendon of the biceps muscle. The needle is inserted on the medial side of the brachial artery.

Block at the wrist: Here the median nerve lies on the medial side of the tendons of the flexor carpi radialis

and to the lateral side of the flexor digitorum superficialis; it usually lies posterior to the tendon of the palmaris longus muscle (sometimes absent).

Ulnar Nerve Block

Indications: Repair of lacerations of the hand and fingers

Procedures: These involve the following:

Block at the elbow: At the elbow, the ulnar nerve enters the forearm between the olecranon process of the ulna

and the medial epicondyle of the humerus. Here the nerve may be palpated and infiltrated with an anesthetic agent.

Block at the wrist: At the wrist, the ulnar nerve enters the hand anterior to the flexor retinaculum and

lateral to the tendons of the flexor carpi ulnaris muscle and the pisiform bone. The ulnar

artery lies on the lateral side of the ulnar nerve. The needle is inserted just lateral to the flexor carpi ulnaris

tendon at the level of the distal transverse crease of the wrist.

Radial Nerve Block

Indications: Repair of lacerations of the hand:

Procedures: These involve the following:

Block at the elbow: At the elbow, the radial nerve descends anterior to the lateral epicondyle of the humerus

in the interval between the brachialis and the brachioradialis muscles. With the elbow joint extended, the lateral edge of the biceps tendon is easily palpated. The needle is inserted halfway between the tendon and the tip of the lateral epicondyle, and the local anesthetic is injected at this point.

Block at the wrist: Just proximal to the wrist, the superficial branch of the radial nerve lies lateral to the radial

artery. The nerve leaves the artery and passes laterally and backward under the tendon of brachioradialis to reach the posterior surface of the wrist. At the level of the proximal transverse flexor crease on the lateral side of the radial artery, the nerve may be infiltrated with an anesthetic solution.

Digital Nerve Blocks

Area of anesthesia: Skin of the fingers. Each finger is supplied by four digital nerves at the 2 o’clock, 5 o’clock, 7 o’clock, and 10 o’clock positions. The palmar digital nerves are derived from the ulnar and median nerves; the dorsal digital nerves are derived from the ulnar and radial nerves. The palmar digital nerves, which arise from the superficial terminal branch of the ulnar nerve in the hand, supply the palmar surface of the medial one and a half fingers, including their nail beds. The dorsal digital nerves, which arise from the dorsal cutaneous branch of the ulnar nerve in the forearm, supply the dorsal surface of the proximal parts of the medial one and a half fingers.

The palmar digital nerves, which arise from the median nerve in the palm, supply the palmar surface of the lateral three and a half fingers, including their nail beds. The dorsal digital nerves, which arise from the superficial branch of the radial nerve, supply the dorsal surface of the proximal parts of the lateral three and a half fingers. The origins of the dorsal digital nerves from the ulnar and radial nerves are subject to variation.

Indications: Repair of lacerations involving individual fingers; removal of nails

Procedures: These involve the following:

Web space method: At the web space, the digital nerves are about to enter the fingers. The needle

is inserted about 0.5 cm, and the nerves are infiltrated with the anesthetic agent. A block on both sides of the fingers adequately deals with the four digital nerves supplying the finger.

Dorsal metacarpal method: A skin wheal of anesthetic is raised between the metacarpal bones on the dorsum of the hand. The needle is inserted through the wheal and advanced slowly forward between the metacarpal bones, stopping just short of the palmarnskin. The anesthetic solution will block the common palmar and dorsal digital nerves.

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Lumbar Spinal Nerve Blocks

Ilioinguinal and Iliohypogastric Nerve Blocks

Area of anesthesia: Skin of the lower part of the anterior abdominal wall

Indications: Repair of lacerations on the anterior abdominal wall

Procedure: 1 in. (2.5 cm) above the anterior superior iliac spine.

Femoral Nerve Block

Area of anesthesia: Skin of the front and medial side of the thigh, extending down the medial side of the knee

and leg, and along the medial border of the foot as far as the ball of the big toe

Indications: Repair of lacerations of the thigh, medial side of the leg, and medial side of the foot

Procedure: Below the midpoint of the inguinal ligament and lateral to the femoral artery.

Sacral Spinal Nerve Blocks

Lateral Cutaneous Nerve of the Thigh Block

Area of anesthesia: Skin of the anterolateral surface of the thigh down to the lateral side of the knee

Indications: Repair of lacerations on the anterolateral surface of the thigh

Procedure: The lateral cutaneous nerve of the thigh (L2 and L3) enters the thigh behind (or through) the lateral end of the inguinal ligament just medial to the anterior superior iliac spine. It then descends anterior or through the sartorius muscle and divides into terminal anterior and posterior

branches.

The nerve may blocked by inserting the anesthetic needle just inferior to the inguinal ligament about 0.5 in. (1.3 cm) medial to the anterior superior iliac spine.

Sciatic Nerve Block

Anterior approach

The anterior approach to a sciatic block is an advanced nerve block technique. The block is well suited for surgery on the leg below the knee, particularly on the ankle and foot. It provides complete anesthesia of the leg below the knee with the exception of the medial strip of skin, which is innervated by the saphenous nerve.

• Indications: Surgery on the knee, tibia, fibula, ankle, and foot

• Landmarks: Femoral crease, femoral artery

Combined with the femoral nerve block, anesthesia of the entire knee and the leg below the knee level is achieved. It should be noted that the anterior approach is less clinically applicable compared to the posterior approach. The sciatic nerve is blocked more distally and a higher level of skill is required to achieve reliable anesthesia.

The patient is in the supine position with both legs fully extended. The following landmarks should routinely be outlined using a marking pen:

Femoral crease

Femoral artery pulse

Needle insertion point marked 4-5 cm distally on the line passing through the pulse of the femoral artery and perpendicular to the femoral crease.



Posterior approach

The posterior approach to sciatic blockade has wide clinical applicability for surgery and pain management of the lower extremity. Consequently, sciatic block is one of the most commonly used techniques in aneshetsia practice.

Indications: Surgery on the knee, tibia, ankle, and foot

Landmarks: Greater trochanter, superior posterior iliac spine, midline between the two

Sciatic nerve blockade results in anesthesia of the skin of the posterior aspect of the thigh, hamstrings and biceps muscles, part of hip and knee joint, and entire leg below the knee, with the exception of the skin of the medial aspect of the lower leg. Depending on the level of surgery, the addition of a saphenous or femoral nerve block may be required.

Landmarks for the posterior approach to sciatic blockade are easily identified in most patients. Proper palpation technique is of utmost importance because the adipose tissue over the gluteal area may obscure these bony prominences. The landmarks are outlined by a marking pen:

Greater trochanter

Posterior-superior iliac spine

Needle insertion point 4-cm distal to the midpoint between landmarks 1 and 2



Popliteal Nerve Block

The popliteal nerve block is a block of the sciatic nerve in the popliteal fossa with the patient in the prone position. The block is ideal for surgeriesof the lower leg, particularly the foot and ankle.

Intertendinous approach:

The popliteal block is one of the most commonly used regional anesthesia techniques in anesthesia practice. Some common indications include corrective foot surgery, foot debridement, and Achilles tendon repair.

Popliteal blockade results in anesthesia of the entire distal two thirds of the lower extremity, with the exception of the medial aspect of the leg.

The following surface anatomy landmarks are used to determine the insertion point for the needle.

Popliteal fossa crease

Tendon of biceps femoris (laterally)

Tendons of semitendinosus and semimembranosus muscles (medially)

The needle insertion point is marked at 7 cm. above the popliteal fossa crease at the midpoint between the tendons.





Common Peroneal Nerve Block

Area of anesthesia: Skin on the anterior and lateral sides of the leg and the dorsum of the foot and toes, including the medial side of the big toe

Indications: Repair of lacerations on the anterior and lateral sides of the leg and the dorsum of the foot and toes

Procedure: Below the head of the fibula

Superficial Peroneal Nerve Block

Area of anesthesia: Skin on the lower anterior and lateral sides of the leg and the dorsum of the foot and toes (except the cleft between the first and second toes, which is innervated by the deep peroneal nerve and the lateral side of the little toe, which is supplied by the sural nerve) Indications: Repair of lacerations in the area of its cutaneous distribution.

Procedure: The superficial peroneal nerve is a branch of the common peroneal nerve. In the lower third of the leg it becomes superficial and its terminal branches pass to their distribution on the dorsum of the foot and toes.

The superficial peroneal nerve is easily blocked in the lower part of the leg by infiltrating the anesthetic in the subcutaneous tissue along a transverse line connecting the medial and lateral malleoli.

Deep Peroneal Nerve Block

Area of anesthesia: Skin in the cleft between the big and second toes

Indications: Repair of lacerations in the cleft between the big and second toes

Procedure: The deep peroneal nerve is a terminal branch of the common peroneal nerve. It descends in the anterior compartment of the leg and at the ankle it passes onto the dorsum of the foot. Here the nerve lies on the lateral side of the dorsalis pedis artery and is superficially placed between the tendons of extensor digitorum

longus and the extensor hallucis longus muscles.

First, the dorsalis pedis artery is palpated midway between the medial and lateral malleoli. With the foot actively dorsiflexed, the tendons of the extensor digitorum longus and extensor hallucis longus muscles can be seen. The nerve lies on the lateral side of the artery between these tendons. The needle is then inserted over the nerve, and the surrounding tissues are infiltrated with anesthetic.

Tibial Nerve Block

Area of anesthesia: Skin of the sole of the foot (medial and lateral plantar nerves)

Indications: Repair of lacerations on the sole of foot

Procedure: The tibial nerve (L4 and L5 and S1 through S3) is the largest terminal branch of the sciatic nerve. At the ankle, the nerve, accompanied by the posterior tibial artery, becomes superficial. It lies behind the medial malleolus, between the tendons of the flexor digitorum longus and the flexor hallucis longus muscles, and is covered by the flexor retinaculum.

The tibial nerve may be blocked as it lies behind the medial malleolus. By careful palpation, the pulsations of the posterior tibial artery can be felt midway between the medial malleolus and the heel. The nerve lies immediately posterior to the artery, and the anesthetic needle can be inserted at this location.

Sural Nerve Block

Area of anesthesia: Skin of the lateral border of foot and lateral side of the little toe

Indications: Repair of lacerations on the lateral side of the foot and little toe

The sural nerve may be blocked by inserting the anesthetic needle midway between the lateral malleolus and the tendo calcaneus (Achilles) and infiltrating the subcutaneous tissue with anesthetic solution.

Saphenous Nerve Block

Area of anesthesia: Skin of the medial side of the leg and the medial border of the foot down as far as the ball of the big toe

Indications: Repair of lacerations on the medial side of the leg and the medial side of the foot

Procedure: The saphenous nerve is a continuation of the femoral nerve and becomes superficial on the medial side of the knee after emerging between the tendons of sartorius and gracilis muscles. The nerve may be blocked by inserting the anesthetic needle on the medial side of the knee joint either over themedial femoral condyle or lower down over the condyle of the tibia. Care should be taken to avoidmthe great saphenous vein. The nerve may also be blocked at the ankle where it passes anterior to the medial malleolus.

Toe Nerve Blocks

Area of anesthesia: Skin of the toes. Each toe is supplied by four digital nerves at the 2 o’clock, 5 o’clock, 7 o’clock, and 10 o’clock positions. The plantar digital nerves are derived from the medial and lateral plantar nerves; the dorsal digital nerves are from the superficial peroneal nerve (except the cleft between the big toe

and second toe, which is supplied by the deep peroneal nerve, and the lateral side of the little toe, which is supplied by the sural nerve.

Indications: Repair of lacerations of the toes, removal of foreign bodies, and removal of nails

Procedure: The nerves are easily blocked with small volumes of anesthetic solution injected subcutaneously and circumferentially around the base of each toe.

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