Interscalene Brachial plexus block

Brachial plexus block is a regional anesthesia technique employed as an alternative or as an adjunct to general anesthesia for surgery of the upper extremity.

It involves the injection of local anesthetic agents in close proximity to the brachial plexus, temporarily blocking the sensation and ability to move the upper extremity.

The subject can remain awake during the ensuing surgical procedure, or they can be sedated or even fully anesthetized if necessary.

Several techniques for blocking the nerves of the brachial plexus are classified by the level at which the needle or catheter is inserted for injecting the local anesthetic — interscalene block on the neck for example is considered the second most complete postoperative analgesia,

Supraclavicular block immediately above the clavicle, infraclavicular block below the clavicle and axillary block in the axilla.

The most important advantage of brachial plexus block is that it allows for the avoidance of general anesthesia and therefore its attendant complications and side effects.

Brachial plexus blockade may be a reasonable option when all of the following criteria are met:

Surgery is expected to be limited to a region between the midpoint of the shoulder and the fingers

There are contraindications to a block such as infection at the intended injection site, significant bleeding disorder, anxiety, allergy or hypersensitivity to local anesthetics.

The brachial plexus is formed by the ventral rami of C5-C6-C7-C8-T1, occasionally with small contributions by C4 and T2.

There are multiple approaches to blockade of the brachial plexus, beginning proximally with the interscalene block and continuing distally with the supraclavicular, infraclavicular, and axillary blocks.

The concept behind all of these approaches to the brachial plexus is the existence of a sheath encompassing the neurovascular bundle extending from the deep cervical fascia to slightly beyond the borders of the axilla.

Brachial plexus block is typically performed by an anesthesiologist.

The tip of the needle should be close to the nerves of the plexus during the injection of local anesthetic solution.

Techniques for obtaining such a needle position include transarterial, elicitation of a paresthesia, and use of a peripheral nerve stimulator or a portable ultrasound scanning device.

The subject may experience a paresthesia or like an electric shock in the arm, hand, or fingers.

A peripheral nerve stimulator connected to an appropriate needle allows emission of electric current from the needle tip to or contacts a motor nerve, characteristic contraction of the innervated muscle may be elicited.

Observation of local anesthetic surrounding the nerves during ultrasound-guided injection is predictive of a successful block.

Interscalene block

The interscalene block is performed by injecting local anesthetic to the nerves of the brachial plexus as it passes through the groove between the anterior and middle scalene muscles, at the level of the cricoid cartilage.

This block is useful in providing anesthesia and postoperative analgesia for surgery to the clavicle, shoulder, and arm.

This bock provides rapid blockade of the shoulder region, and relatively has easily palpable anatomical landmarks.

The disadvantages of this block include inadequate anesthesia in the distribution of the ulnar nerve, which makes this an unreliable block for operations involving the forearm and hand.

Temporary paresis of the thoracic diaphragm occurs in virtually all people who have undergone interscalene or supraclavicular brachial plexus block.

Significant respiratory impairment can be demonstrated in these people by pulmonary function testing.

In those with severe chronic obstructive pulmonary disease this procedure can result in respiratory failure requiring tracheal intubation and mechanical ventilation until the block dissipates.

Horner’s syndrome may be observed if the local anesthetic solution tracks cephalad and blocks the stellate ganglion, and may be accompanied by difficulty swallowing and vocal cord paresis.

These signs and symptoms are transient.

Contraindications to interscaline block include severe chronic obstructive pulmonary disease, and paresis of the phrenic nerve on the opposite side as the block.

Supraclavicular block

The supraclavicular block is ideal for operations involving the arm and forearm, from the lower humerus down to the hand.

The brachial plexus is most compact at the level of the trunks formed by the C5–T1 nerve roots, so nerve block at this level has the greatest likelihood of blocking all of the branches of the brachial plexus.

This results in rapid onset times and, ultimately, high success rates for surgery and analgesia of the upper extremity, excluding the shoulder.

The appropriate location for injection of local anesthetic, which is typically lateral to the lateral border of the sternocleidomastoid muscle and above the clavicle, with the first rib generally considered to represent the limit below which the needle must not be directed.

The pleural cavity and uppermost part of the lung are located at this level.

Palpation or ultrasound visualization of the subclavian artery just above the clavicle provides a useful anatomic landmark for locating the brachial plexus, which is lateral to the artery at this level.

Proximity to the brachial plexus can be determined by elicitation of a paresthesia, use of a peripheral nerve stimulator, or ultrasound guidance.

A supraclavicular block elicitis a more complete block of the median, radial ulnar and musculocutaneous nerves, but does not improve postoperative analgesia.

The supraclavicular block is often quicker to perform and may result in fewer side effects than the interscalene block.

An infraclavicular block and axillary blocks achievement adequate anesthesia for surgery of the upper extremity and is about the same with supraclavicular block.

Compared with interscalene block which can result in diaphragmatic hemiparesis in all individuals, only half of those who undergo supraclavicular block experience this side effect.

Disadvantages of the supraclavicular block include the risk of pneumothorax, which is estimated to be between 1%–4% when using paresthesia or peripheral nerve stimulator guided techniques.

Using Uultrasound guidance allows visualization the first rib and the pleura, helping to ensure that the needle does not puncture the pleura; this presumably reduces the risk of pneumothorax.

Infraclavicular block

When compared to a multiple-stimulation axillary block, infraclavicular block provides similar efficacy.

However it may be associated with a shorter performance time and less procedure-related pain for the patient.

The axillary block is particularly useful in providing anesthesia and postoperative analgesia for surgery to the elbow, forearm, wrist, and hand.

The axillary block is also the safest of the four main approaches to the brachial plexus, as it does not risk paresis of the phrenic nerve, nor does it have the potential to cause pneumothorax.

In the axilla, the nerves of the brachial plexus and the axillary artery are enclosed together in a fibrous sheath which is a continuation of the deep cervical fascia.

The easily palpated axillary artery thus serves is a landmark for this block, and the injection of local anesthetic close to this artery frequently leads to a good block of the brachial plexus.

The axillary block is commonly performed due to its ease of performance and relatively high success rate.

Disadvantages of the axillary block include inadequate anesthesia in the distribution of the musculocutaneous nerve.

The musculocutaneous nerve supplies motor function to the biceps, brachialis, and coracobrachialis muscles and one of its branches supplies sensation to the skin of the forearm.

Single-injection techniques provide unreliable blockade in the areas supplied by the musculocutaneous and radial nerves.

Injections on the musculocutaneous, median and radial nerves is the best technique for the axillary block.

Using ultrasound to follow the spread of local anesthetic demonstrated an improved success rate of the block, relative to blocks done with nerve stimulator alone) even at the inferior roots of the plexus.

There is some evidence to suggest that the use of ultrasound guidance in combination with nerve stimulation can shorten the performance time of supraclavicular block.

For axillary block, success rates are greatly improved with multiple injection techniques whether using nerve stimulation or ultrasound guidance.

The duration of a single-shot brachial plexus block is highly variable, commonly lasting anywhere from 45 minutes to 24 hours.

The block duration can be extended by placing an indwelling catheter, which may be connected to a mechanical or electronic infusion pump for continuous administration of local anesthetic solution.

A catheter may be inserted at the interscalene, supraclavicular, infraclavicular or axillary location, depending on the desired location of nerve block.

Brachial plexus block can be associated with infection or bleeding.

In people who are using anticoagulant agents, there is a greater risk of complications related to bleeding.

Complications associated with brachial plexus block include intra-arterial or intravenous injection, which can lead to local anesthetic toxicity, serious central nervous system problems such as epileptic seizure, central nervous system depression, and coma.

Cardiovascular effects of local anesthetic toxicity include slowing of the heart rate and impairment of its ability to pump blood through the circulatory system, which may lead to circulatory collapse. In severe cases, cardiac dysrhythmia, cardiac arrest and death may occur.

Other rare but serious complications from brachial plexus block include pneumothorax and persistent paresis of the phrenic nerve.

Complications associated with interscalene and supraclavicular blocks include inadvertent subarachnoid or epidural injection of local anesthetic, which can result in respiratory failure.

Because of the close proximity of the lung to the brachial plexus at the level of the clavicle, the complication most often associated with this block is pneumothorax: risk as high as 6.1%.

Further complications of supraclavicular block include subclavian artery puncture, and spread of local anesthetic to cause paresis of the stellate ganglion, the phrenic nerve and recurrent laryngeal nerve.

Potential complications: Temporary weakness in the arm/hand Horner’s syndrome (drooping eyelid, constricted pupil) Phrenic nerve block causing temporary diaphragm weakness Rare but serious complications like pneumothorax or nerve injury The block typically lasts 12-24 hours depending on the anesthetic used, providing significant pain relief during the most uncomfortable period after surgery.​​​​​​​​​​​​​​​​