Brachial plexus block
This technique 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 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.
Commonly employed 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.
[2] Temporary paresis (impairment of the function) of the thoracic diaphragm occurs in virtually all people who have undergone interscalene or supraclavicular brachial plexus block.
[7] In certain people — such as those with severe chronic obstructive pulmonary disease — this can result in respiratory failure requiring tracheal intubation and mechanical ventilation until the block dissipates.
[citation needed] Contraindications include severe chronic obstructive pulmonary disease,[8] and paresis of the phrenic nerve on the opposite side as the block.
This results in rapid onset times and, ultimately, high success rates for surgery and analgesia of the upper extremity, excluding the shoulder.
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.
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.
[12] 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.
[11] Despite the fact that people have been performing brachial plexus blocks for over a hundred years,[14] there is as yet no clear evidence to support the assertion that one method of nerve localization is better than another.
On the other hand, use of ultrasound may create a false sense of security in the operator, which may lead to errors, especially if the needle tip is not adequately visualized at all times.
[11] For axillary block, success rates are greatly improved with multiple injection techniques whether using nerve stimulation or ultrasound guidance.
The block 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.
[2] Complications associated with brachial plexus block include intra-arterial or intravenous injection, which can lead to local anesthetic toxicity.
[18] Complications associated with interscalene and supraclavicular blocks include inadvertent subarachnoid or epidural injection of local anesthetic, which can result in respiratory failure.
[25] In January 1900, Harvey Cushing (1869–1939) — who was at that time one of Halsted's surgical residents — applied cocaine to the brachial plexus prior to dividing it, during a forequarter amputation for sarcoma.
The needle was inserted above the midpoint of the clavicle where the pulse of the subclavian artery could be felt and it was directed medially toward the second or third thoracic spinous process.
[29] By the late 1940s, clinical experience with brachial plexus block in both peacetime and wartime surgery was extensive,[30] and new approaches to this technique began to be described.
He secured a needle in the supraclavicular fossa and attached tubing connected to a syringe through which he could inject incremental doses of local anesthetic.
[citation needed] In 1977, Selander described a technique for continuous brachial plexus block using an intravenous catheter secured in the axilla.
The Sims approach, now referred to as Infracoracoid Block has certain advantages: a) The needle tip is directed away from the apex of the lung, not toward it, b) the skin at the point of initial needle penetration is easier to clean than the axilla, c) the Musculocutaneous nerve is still within the sheath at this point making this terchnique more consistently useful for upper forearm surgery, and d) a percutaneous indwelling catheter may be placed for postoperative pain control.
