Brachial plexus block

Brachial plexus block is a regional anesthesia technique that is sometimes employed as an alternative or as an adjunct to general anesthesia for surgery of the upper extremity. 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 subject can remain awake during the ensuing surgical procedure, or s/he can be sedated or even fully anesthetized if necessary. Brachial plexus block is a regional anesthesia technique that is sometimes employed as an alternative or as an adjunct to general anesthesia for surgery of the upper extremity. 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 subject can remain awake during the ensuing surgical procedure, or s/he can be sedated or even fully anesthetized if necessary. There are several techniques for blocking the nerves of the brachial plexus. These techniques are classified by the level at which the needle or catheter is inserted for injecting the local anesthetic — interscalene block on the neck, supraclavicular block immediately above the clavicle, infraclavicular block below the clavicle and axillary block in the axilla (armpit). General anesthesia may result in low blood pressure, undesirable decreases in cardiac output, central nervous system depression, respiratory depression, loss of protective airway reflexes (such as coughing), need for tracheal intubation and mechanical ventilation, and residual anesthetic effects. 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. Although brachial plexus block is not without risk, it usually affects fewer organ systems than general anesthesia. Brachial plexus blockade may be a reasonable option when all of the following criteria are met: 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. To achieve an optimal block, the tip of the needle should be close to the nerves of the plexus during the injection of local anesthetic solution. 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. If the needle is close to or contacts a nerve, the subject may experience a paresthesia (a sudden tingling sensation, often described as feeling like 'pins and needles' or like an electric shock) in the arm, hand, or fingers. Injection close to the point of elicitation of such a paresthesia may result in a good block. A peripheral nerve stimulator connected to an appropriate needle allows emission of electric current from the needle tip. When the needle tip is close to or contacts a motor nerve, characteristic contraction of the innervated muscle may be elicited. Modern portable ultrasound devices allow the user to visualize internal anatomy, including the nerves to be blocked, neighboring anatomic structures and the needle as it approaches the nerves. Observation of local anesthetic surrounding the nerves during ultrasound-guided injection is predictive of a successful block. Appropriate block per site-specific procedure are listed in the following table: 1. Include musculocutaneous nerve2. Include T1-T2 if block is anesthetic3. Include C3-C4 if block is anesthetic 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 particularly useful in providing anesthesia and postoperative analgesia for surgery to the clavicle, shoulder, and arm. Advantages of this block include rapid blockade of the shoulder region, and relatively easily palpable anatomical landmarks. 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 (impairment of the function) 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 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.Horner's syndrome may be observed if the local anesthetic solution tracks cephalad and blocks the stellate ganglion. This may be accompanied by difficulty swallowing and vocal cord paresis. These signs and symptoms are transient however, and do not commonly result in any long-term problems, although they may be significantly distressing to patients until the effects subside. Contraindications include severe chronic obstructive pulmonary disease, and paresis of the phrenic nerve on the opposite side as the block.