Regional anesthesia and the incorporation of peripheral nerve blocks allows for localized, targeted anesthesia for both surgical anesthesia and post-operative pain control. By focusing on a specific location, systemic, generalized adverse effects can be avoided. To perform a peripheral nerve block, the provider must have the appropriate equipment (peripheral nerve needles, local anesthetics) and a targeted nerve structure. Surgical duration should be taken into account when choosing a local anesthetic for a true surgical block. Literature has shown that one of the most important factors is the mass or total dosage of the local anesthetic. Multiple adjuncts can be used in combination with local anesthetics to decrease the time of onset, increase duration, and increase the quality and density of the block.
When deciding which upper extremity block to use, it is important to know the anatomy of the brachial plexus. The brachial plexus is derived from the C5 to T1 nerve roots. The nerve roots exit from their respective intervertebral foramina, travel between the anterior and middle scalene muscles, and begin to form the brachial plexus. At the most proximal portion of the brachial plexus, the nerve roots form three trunks: the upper trunk, the middle trunk, and the lower trunk. The three trunks pass over the first rib, and as they pass under the clavicle, they form two divisions: the anterior division and the posterior division. Distal to the clavicle the divisions form three cords: the lateral cord, the posterior cord, and the medial cord. Each cord then gives off a branch and ultimately becomes a terminal nerve. There are many mnemonics to remember the order of structures for the brachial plexus; one of the most common ones is “Randy Travis Drinks Cold Beers,” which stands for roots, trunks, divisions, cords, and branches, respectively. When choosing which block to use one must consider which part of the brachial plexus they are targeting - roots, trunks, divisions, cords, or branches - and decide to perform an interscalene, supraclavicular, infraclavicular, or axillary block, respectively. Certain cutaneous portions of the upper extremity may need additional, separate blocks such as the anterior shoulder, which has contributions from the C1-C4 (superficial plexus), and the medial upper arm, which has contributions from T2 (intercostobrachial).
The indications for upper extremity peripheral nerve blocks are for surgical anesthesia as well as post-operative pain management for surgeries involving either the upper arm or forearm. Each upper extremity block has its own indications based on the location of the surgery. The interscalene block is typically indicated for shoulder surgery but is not sufficient for surgeries distal to the elbow. The supraclavicular is a great peripheral nerve block that encompasses the entire arm. The infraclavicular and the axillary nerve blocks are indicated for surgeries involving the elbow and below the elbow, respectively.
Contraindications to peripheral nerve blocks are the patient refusing or unable to consent, coagulopathy or anticoagulation use, ongoing infection, and abnormal anatomy that obscures the trajectory of the needle which makes it difficult or nearly impossible to target the appropriate structures.
The following are the brachial plexus blocks from proximal to distal in anatomical order of the brachial plexus: interscalene, supraclavicular, infraclavicular, and axillary.
The interscalene block targets the C5, C6, and C7 nerve roots at the level of the roots. The provider should ask the patient to turn their head away from the side of interest. At the lateral edge of the sternocleidomastoid (SCM), the interscalene groove can be palpated. With ultrasound guidance, the three nerve roots can be appreciated as three distinct hypoechoic circular structures situated between the two scalene muscles. The patient’s neck should be cleaned in a sterile fashion, and appropriate equipment and needles should be at available at the bedside. A suitable needle should be advanced in-plane, aiming between the C5 and C6 nerve root. As the needle traverses the fascia, encompassing the nerve roots, a distinct pop should be felt. Once in the desired position, confirmed on ultrasound, negative aspiration should be applied before injecting the desired volume of local anesthetic. The interscalene block is indicated for upper arm surgeries involving the shoulder. The ulnar distribution is spared; therefore, this block should not be used for surgeries involving the forearm and/or wrist. A properly performed interscalene block almost always results in some form of ipsilateral phrenic nerve paralysis. For this reason, practitioners should avoid or consider risk versus benefits for patients who have an underlying respiratory disease, such as advanced COPD. Other potential complications include Horner syndrome which presents as a triad of ptosis, miosis, and anhidrosis.
The supraclavicular block targets the trunks (and divisions) of the brachial plexus. The patient is asked to turn their head away from the side of interest. With ultrasound guidance, obtain a circular view of the subclavian artery by placing the ultrasound probe parallel to the clavicle. The brachial plexus, found lateral and superior to the subclavian artery, appears as either three hypoechoic circles resembling a “stoplight” when more proximal (representing the trunks of the brachial plexus) or as a cluster of five to six smaller hypoechoic circles (representing the divisions of the brachial plexus). A suitable needle should be advanced to target these structures. Once in the desired position, confirmed on ultrasound, negative aspiration should be applied before injecting the desired volume of local anesthetic. If in the correct position, the local anesthetic should spread circumferentially around the nerve bundle, giving the bundle a floating appearance. The interscalene block provides anesthesia for the entire arm. Complications for the supraclavicular are similar to those of the interscalene block, phrenic nerve paralysis, and Horner syndrome; however, they are less likely than with the interscalene approach. Pneumothorax, however, is a more likely complication with this approach than the interscalene approach.
The infraclavicular block targets the divisions and cords of the brachial plexus and provides anesthesia for the hand, forearm, elbow, and upper arm. It is more difficult to visualize the target structures with this approach, which has caused this block to fall out of favor for most practitioners. The patient is asked to turn their head away from the side of interest. With ultrasound guidance, the practitioner obtains a circular view of the subclavian artery by placing the ultrasound probe inferior and perpendicular to the clavicle. The practitioner places the needle almost adjacent to the clavicle (superior to the short end of the probe). The needle should be directed at the inferior border of the subclavian artery. A suitable needle should be advanced to target these structures. Once in the desired position, confirmed on ultrasound, negative aspiration should be applied before injecting the desired volume of local anesthetic. The nerves next to the subclavian artery to local anesthetic spread around the artery should provide sufficient block. Complications to keep in mind for this particular approach are pneumothorax, chylothorax (if on the left side), hemothorax, intravascular injection, or trauma.
The axillary block is performed at the level of the branches and is most useful for procedures involving the forearm. Using ultrasound guidance, the probe should be placed in the patient's axilla to locate the axillary artery in a cross-sectional view, which will appear as a circle. The target nerves surrounding the artery are the radial, median, and ulnar nerves. A suitable needle should be advanced to target these structures. Once in the desired position, confirmed on ultrasound, negative aspiration should be applied before injecting the desired volume of local anesthetic. To obtain a complete block distal to the elbow, the musculocutaneous nerve, located in the belly of the coracobrachialis muscle, must be targeted as well.
While complications are rare, one must know possible complications that may result from peripheral nerve blocks such as nerve root injury, paresthesias, intrathecal or epidural injection, injury/trauma to surrounding structures, pneumothorax, vascular injury, infection/abscess formation, muscle trauma, and local anesthetic toxicity with central nervous system and cardiovascular compromise. It is also important to realize which complications have the highest occurrence rate at any location (see above techniques). There is also always the risk of an unsuccessful block.
Upper extremity blocks are useful as both surgical anesthesia, and more often, successful postoperative analgesia, reducing intra-operative and postoperative opioid requirements. Ultrasound guidance has become the standard of care when performing the interscalene, supraclavicular, infraclavicular, and axillary blocks. Blocks targeting the brachial plexus can complement general anesthesia and work by providing multimodal anesthesia. Multimodal anesthesia allows for fewer postoperative opioids, leading to a decrease in opioid-related adverse effects such as respiratory depression, oversedation, and nausea and vomiting. Multimodal pain management has also shown to increase both patient and surgeon satisfaction.
Ultrasonography is the preferred method to localize the targeted nerve. The use of ultrasound allows for direct visualization. Recent research shows that the use of ultrasound as a standard of care has had beneficial and positive effects on patient satisfaction, surgeon satisfaction, duration and intensity, reduced procedure time, the onset of block effect, as well as reduced overall adverse outcomes. Direct visualization of the needle can help experienced providers avoid intraneural injection and injury as well as intravascular injection and possibly local anesthetic toxicity. These studies thus far are on a smaller scale and encompass expert opinions; futures studies should be done on a larger scale to confirm these opinions and reaffirm the findings from smaller studies. (Level III)
In a team setting, it is imperative that closed loop communication exists. All patient should have a proper time out performed. The name of the patient, date of birth, any pertinent allergies, and the procedure the patient is having should all be confirmed between all providers (anesthesiologist, nurse, surgeon, et al.) as well as with the patient. All consents should be signed after thorough risks, benefits, and expectations have been explained in detail to the patient. It is crucial that site verification and laterality is confirmed before beginning any procedure. The implementation of guidelines and checklists have proven to reduce the occurrence of adverse outcomes such as surgeon-anesthesiologist miscommunications and wrong-site/wrong-side regional anesthesia procedures. (Level I)