The patient is in semi-sitting supine position with the head facing away from the side to be anesthetized. The premedication of an adult, average size patient typically consists of 2-4 mg of midazolam; 250mcg -500mcg of alfentanyl administered just before insertion of the needle TIP: Visualization of the brachial plexus in the interscalene grove can be challenging in patients who are tense, moving or exhibit guarding. Proper sedation can go a long way toward obtaining quality images.
The ultrasound probe (10-12MHz) is applied in the axial oblique plane closer to the midline and angled to first visualize the carotid artery
Note the position of the internal jugular vein (IJ) as the pressure on the ultrasound probe is lightened. The internal jugular vein is positioned slightly superficially and lateral to the carotid artery. Changing the pressure on the probe causes the IJ to open and close.
The ultrasound probe is then moved slightly laterally to visualize the brachial plexus in the interscalene grove between anterior and middle scalene muscles. The roots/trunks (N) of the brachial plexus are seen stacked between the scalene muscles usually as round, hypoechoic structures
Sliding or angling the ultrasound probe slightly more inferior allows visualization in the low-interscalene position in which the brachial plexus is positioned in proximity to the subclavian artery
After the brachial plexus is identified on the image, a 50 mm (max) stimulating needle is inserted perpendicular to the long axis of the ultrasound probe. The needle is inserted at the point on the probe that corresponds to the location of the brachial plexus on the screen The needle insertion results in shadowing of the ultrasound image which indicates the path of the needle TIP: Make sure to estimate the exact depth of the brachial plexus (typically 0.5-1.5 cm) before inserting the needle. The needle should never be inserted deeper than the depth indicated on the ultrasound image.
Injection of local anesthetic is made with monitoring of the dispersion of the injectate. If the injectate does not appear to fill the lower compartment of the interscalene space, the needle is slightly advanced (0.5-1cm) and additional injection is made at a slightly greater depth (0.5-1cm deeper). Local anesthetic is injected slowly and with frequent aspirations, while avoiding excessive injection pressures (<20 psi). Thirty to forty ml of local anesthetic is more than adequate for reliable blockade of the brachial plexus. Typical indications for this block are surgery on the shoulder, lateral clavicle, acromioclavicular joint, proximal humerus and elbow (with low interscalene block).
POSITIONING The patient is placed supine The patients head is turned toward the contralateral side The operator is positioned on the ipsilateral side The ultrasound machine should be placed on the contralateral side SONOANATOMY. The subclavian artery appears hypoechoic and pulsatile and the individual nerves as hypoechoic small circles. It is very important to identify the pleura while performing this block so as to avoid pneumothorax. The first rib acts as a backstop to prevent pleural puncture, which means that the needle tip is in the same plane
The major advantage of the supraclavicular approach is that the nerves are very tightly packed, so that the onset is fast and the blockade deep, leading to this technique being nicknamed the spinal of the arm. Ultrasound guidance, the pleura can be visualized, and as long as proper technique is used, i.e. if the needle, and especially the needle tip, is visualized at all times, pneumothorax should not occur. It will not diffuse to the lower roots of the cervical plexus, and thus will not block the upper aspect of the shoulder. Typical Indication : For surgeries below the mid-humerus level. Twenty to Forty mls local anaesthetic is adequate for reliable block
Peripheral Nerve Injury Most nerve injury presents as residual paresthesia, hand or forearm hypoesthesia, and rarely as permanent Paresis The overall incidence of long-term nerve injury ranges between 0.02% and 0.4% Vascular Injury The risk of hematoma immediately after brachial plexus techniques is small (0.001 to 0.02%) Muscle Injury Myonecrosis from local anesthetics at concentrations typically achieved at the site of injection is well proven and characteristic of all local anesthetics, with bupivacaine producing the most intense effect. Because damage is dose related, continuous local anesthetic administration may worsen injury. Possible Complications
Hemidiaphramatic Paresis The proximity of the phrenic nerve to the interscalene groove frequently leads to unintended local anesthetic block and resultant diaphragmatic dysfunction. The incidence of hemidiaphragmatic paresis (HDP) is 50-100% after interscalene brachial plexus block Pneumothorax The reported incidence of pneumothorax after supraclavicular block is 0.5% to 6.1% Intravascular Injection local anesthetic injected directly into the vertebral or carotid artery, or retrograde flow of local anesthetic via the subclavian artery, may proceed directly to the brain.
Subarachnoid or Epidural Injection. Interscalene brachial plexus block has been linked to unintended subarachnoid block and to cervical or thoracic epidural block. Cervical Sympathetic Chain. Excessive local anesthetic spread can also affect the cervical sympathetic chain, causing the patient to manifest Horners syndrome. with20% to 90% incidence Recurrent Laryngeal Nerve. Hoarseness may transpire after interscalene block or after 1.3% of supraclavicular blocks
Ultrasound guidance with real-time needle visualization in relation to anatomic structures and target nerves makes regional anesthesia safer and more successful. With ultrasound guidance in experienced hands, brachial plexus blockade can lead to Decreased block performance and onset time, Increased success rate and Decreased rate of complications. These advantages result in increased operating room efficiency, as well as increased patient satisfaction. Advantages of Ultrasound Guidance
The infraclavicular block is a blockade of the brachial plexus below the level of the clavicle and in the proximity of the coracoid process. This block is uniquely well-suited for hand, wrist, elbow, and distal arm surgery. It also provides excellent analgesia for an arm tourniquet. As opposed to a supraclavicular block, an infraclavicular block is not a good choice for shoulder surgery.
The boundaries of the infraclavicular fossa are the pectoralis minor and major muscles anteriorly, ribs medially, clavicle and the coracoid process superiorly, and humerus laterally. At this location, the brachial plexus is composed of cords. The sheath surrounding the plexus is delicate. It contains the subclavian/axillary artery and vein. Axillary and musculocutanous nerves leave the sheath at or before the coracoid process in 50% of patients. Consequently, the deltoid and biceps twitches should not be accepted as reliable signs of brachial plexus identification. Anatomic structures of importance. Pectoralis muscle (shown cut to expose brachial plexus) clavicle (removed) coracoid process humerus brachial plexus subclavian/axillary artery and vein
The patient is in the supine position with the head facing away from the side to be blocked. The anesthesiologist also stands opposite to the side to be blocked to assume an ergonomic position during the block performance. It is best to keep the arm abducted and flexed in the elbow to keep the relationship of the landmarks to the brachial plexus constant. Attention should be paid when the arm is supported at the wrist to allow clear unobstructed detection of the twitches of the hand
Surface Landmarks The following surface anatomy landmarks are useful in identifying the estimated site for an infraclavicular block: 1.Sternoclavicular joint 2.Medial end of the clavicle 3.Coracoid process 4.Acromioclavicular joint 5.Head of the humerus Anatomic Landmarks Landmarks for the infraclavicular block include: 1.Coracoid Process 2.Medial clavicular head 3.Midpoint of line connecting 1 and 2 and 3cm caudal The needle insertion site is marked approximately 3cm caudal to the midpoint of the line connecting points 1 and 2.
TIP: Palpation of the bony prominence just medial to the shoulder, while the arm is elevated and lowered, identifies the coracoid process. As the arm is lowered, the coracoid process meets the fingers of the palpating hand. This maneuver should be used to identify the coracoid process in each patient planned for an infraclavicular block
Needle insertion A 10-cm long, 22-gauge insulated needle, attached to a nerve stimulator, is Inserted at a 45-degree angle to the skin and Advanced parallel to the line connecting the medial clavicular head with the coracoid process. The nerve stimulator is initially set to deliver 1.5 mA. A local twitch of the pectoralis muscle is typically elicited as the needle is advanced beyond the subcutanous tissue. Once the pectoralis twitches disappear, the needle advancement should be slow and methodical while looking for the twitch of the brachial plexus
TIPS: When the pectoralis twitch is absent despite appropriately deep needle insertion, the landmarks should be checked as the needle is most likely inserted too cranially (underneath the clavicle). The bevel of the needle should be facing down to facilitate nerve stimulation and reduce the risk of vascular puncture (subclavian or axillary artery and vein). Brachial plexus stimulation is typically obtained at a depth of 5 to 8 cm. Twitches from the biceps or deltoid muscles should not be accepted, since the musculocutaneous and axillary nerve, respectively, may depart the brachial sheath before the caracoid process