Supraclavicular Brachial Plexus Block
Carlo D. Franco, MD
Chairman Orthopedic Anesthesiology
JHS Hospital of Cook County
Associate Professor Departments of
Anesthesiology and
Anatomy and Cell Biology
Rush University Medical Center
Mailing Address:
JHS Hospital of Cook County
Department of Anesthesiology, Suite # 5670
1901 West Harrison St
Chicago, IL 60612
Phone (312) 864 3217
Fax (312) 864 9549
E-mail carlofra@aol.com
Contents
ANATOMY OF THE BRACHIAL PLEXUS ABOVE THE CLAVICLE
LOCAL ANESTHETIC CHOICES FOR SINGLE-SHOT AND CATHETER TECHNIQUES
The supraclavicular block is one of several techniques used to accomplish anesthesia of the brachial plexus. The block is performed at the level of the brachial plexus trunks where the almost entire sensory, motor and sympathetic innervation of the upper extremity is carried in just three nerve structures confined to a very small surface area. Consequently, typical features of this block include rapid onset, predictable and dense anesthesia (1-3). Kulenkampff in Germany in 1911 performed the first percutaneous supraclavicular approach, reportedly on himself, a few months after Hirschel described a surgical approach to the brachial plexus in the axilla. The technique was later published in 1928 by Kulenkampff and Persky (4). As described, the technique was performed with the patient in the sitting position (“a regular chair will suffice”) or in the supine position with a pillow between the shoulders if the patient could not adopt the sitting position. The operator sat on a stool at the side of the patient. 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 towards the spinous process of T2 or T3. Kulenkampff familiarity with brachial plexus anatomy allowed him to recognize that “the best way to reach the trunks was in the neighborhood of the subclavian artery over the first rib”. His technique was also simple “all the branches of the plexus could be anesthetized through one injection”. These two assertions are still valid today. Unfortunately his advice on needle direction carried an inherited high risk of pneumothorax. The popularity of the supraclavicular block remained unrivaled during the entire first half of the 20th century way until after World War II. During this time the technique underwent several modifications, most of them intending to deal with the risk of pneumothorax (1, 5-8).
The introduction of axillary techniques by Accardo and Adriani (9) in 1949 and especially by Burnham (10) in 1958 marked the beginning of the decline in interest for supraclavicular block. The axillary block was particularly popularized after a publication in Anesthesiology by De Jong in 1961.(11) The paper was based on cadaver dissections and included the now well known calculation of 42 mL as the volume needed to fill a cylinder 6 cm long (axillary sheath), that according to De Jong “should be sufficient to completely bathe all branches of the brachial plexus”. The article was also critical of the supraclavicular approach. Coincidentally the same journal published a paper by Brand and Papper (12) who compared axillary and supraclavicular techniques and warned off the 6.1% rate of pneumothorax frequently quoted for supraclavicular block.
More modern modifications of supraclavicular block include Winnie and Collins’s subclavian perivascular technique (13) and the “plumb-bob” technique of Brown and collaborators (14). The former is more a concept than a radically different technique, stating that plexus anesthesia is performed around a main vessel (perivascular) and within the confines of a sheath. Otherwise, their technique is similar to Murphey’s (7) who in 1944 had described a single injection technique performed just lateral to the anterior scalene muscle directing the needle caudad. The latter was published in 1993 by Brown et al and is commonly known as “plumb-bob” approach. It is based on cadaver dissections and magnetic resonance imaging performed on volunteers. In this technique the needle is introduced above the clavicle, just lateral to the sternocleidomastoid (SCM) muscle and advanced perpendicularly to the plexus in an anteroposterior direction (“plumb bob”). If the needle misses the plexus the pleural dome could be penetrated.
Many authors perceive supraclavicular block technique as complex, associated with a significant risk of pneumothorax. However, the advantages of a supraclavicular technique, namely its rapid onset, dense and predictable anesthesia along with its high success rate make it a very useful approach, that according to Brown et al (14) is “unrivaled” by other techniques. Indeed, in our practice the supraclavicular approach is the cornerstone of upper extremity regional anesthesia and we use it extensively in many patients (15).
The supraclavicular block is a technique that can be used to provide anesthesia for any surgery on the upper extremity that does not involve the shoulder. It is an excellent choice for elbow and hand surgery.
There are general contraindications that apply to any regional block like infection of the area, clinically significant coagulation abnormalities and personality disorders or mental illness that prevent the patient from lying still during surgery.
More specifically, this block is classically not attempted bilaterally because of the potential risk of respiratory emergency in case of pneumothorax or phrenic nerve block. While this recommendation seems logical the evidence is lacking in the literature.
ANATOMY OF THE BRACHIAL PLEXUS ABOVE THE CLAVICLE
The brachial plexus is usually formed by five roots originating from the ventral divisions of C5 through T1. The roots are sandwiched between the anterior and middle scalene muscles. The anterior scalene muscle originates in the anterior tubercles of the transverse processes of C3 to C6 and inserts on the scalene tubercle of the upper surface of the first rib. The middle scalene muscle originates in the posterior tubercles of the transverse processes of C2 to C7 and inserts on the upper surface of the first rib behind the subclavian groove. The five roots converge toward each other to form three trunks -upper, middle and lower-, which are stacked one on top of the other as they traverse the triangular interscalene space formed between the anterior and middle scalene muscles, commonly known as interscalene groove. This space becomes wider in the anteroposterior plane as the muscles approach their insertion on the first rib. The subclavian artery accompanies the brachial plexus in the interscalene triangle anterior to the lower trunk. While the roots of the plexus are long, the trunks are almost as short as they are wide, soon giving rise to anterior and posterior divisions as they reach the clavicle. Figure 1 shows clinical anatomy of the brachial plexus and surrounding structures in the supraclavicular area.
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Figure 1. Cadaver dissection of left supraclavicular area. The SCM muscle has been removed. The roots and trunks of the plexus are visible lateral to the anterior scalene muscle. The trunks are all supraclavicular. The suprascapular nerve is seen arising from the upper trunk just proximal to the origin of the anterior and posterior divisions of this trunk. The phrenic nerve is visible in front of anterior scalene. Medial to it the origin of vertebral artery can be seen and more medially the common carotid artery and vagus nerve. The first intercostal space is visualized below the clavicle. |
There are two potential places where the pleura can be injured during a supraclavicular block leading to pneumothorax. Those are the pleural dome and the first intercostal space. The pleural dome is the apex of the parietal pleura (inside lining of the rib cage), circumscribed by the first rib. Each first rib is short, broad and flattened bone structure with the shape of a letter “C”. They are located on each side of the upper chest with their concavities facing each other. This concavity or medial border forms the outer boundary of the pleural dome. The anterior scalene, by inserting in this border of the first rib, comes in contact medially with the pleural dome. There is no pleural dome lateral to the anterior scalene muscle. The first intercostal space on the other hand, is for the most part infraclavicular (see figure 1) and consequently should not be reached when a supraclavicular block is properly performed, as it will be explained later.
Clinical Pearls
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With the shoulder pulled down the three trunks of the brachial plexus are located above the clavicle; therefore the block needle during a supraclavicular block should never need to reach below the clavicle.
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The first intercostal space is located below the clavicle, thus its penetration is unlikely during a supraclavicular block properly performed.
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The needle should never cross the parasagital plane medial to the anterior scalene muscle because of risk of pneumothorax.
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The pulsatile effect of the subclavian artery exerted mainly against the lower trunk could explain why the C8-T1 dermatome can be spared if the injection is not performed in the vicinity of the lower trunk.
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The SCM muscle inserts on the medial third of the clavicle, the trapezius muscle on the lateral third of it, leaving the middle third for the neurovascular bundle. These proportions are maintained regardless of patient’s size. Bigger muscle bulk through exercise does not influence the size of the muscle insertion area.
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The brachial plexus crosses the clavicle at or near its midpoint. Because of the direction of the brachial plexus from medial to lateral as it descends, the higher in the supraclavicular area the more medial (closer to the SCM) the plexus is located.
The technique described in this chapter combines the simplicity of the original single injection Kulenkampff technique with important anatomical principles, which should make the technique safer than the original description. The main landmarks for this block are the lateral insertion of the SCM muscle in the clavicle, the clavicle itself and the midline of the patient. These three landmarks are easily identifiable in the majority of patients.
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Gloves
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Antiseptic solution for skin disinfection
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Marking pen
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Sterile gauze
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Two 20-mL syringes for local anesthetic solution
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One 1-ml syringe with a 25-gauge needle for skin wheal
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One 5-cm, short-bevel 22-gauge insulated needle
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Surface electrode
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Nerve stimulator
Ideally the block is performed in a dedicated regional anesthesia room. However, regardless as to whether the block is performed inside or outside the OR, the location must include ASA standard monitors, oxygen source, suctioning, resuscitation equipment and drugs. A contingency plan for emergencies must be in place to deal safely and expeditiously with any emergency that might arise.
If not contraindicated, this block is best performed after appropriate, light premedication (e.g., midazolam 1 mg (IV) plus fentanyl 50 mcg IV for the average adult). In young and healthy patients this dose can be repeated as necessary. The patient is best kept sedated but cooperative and able to relate pain or any undue discomfort.
Our technique is a single-injection, nerve-stimulator technique. The block is performed with the patient in a semi-sitting position with the head rotated to the opposite side as shown in Figure 2A. The semi-sitting position is more comfortable than the supine position both for the patient and the operator. Because patient positioning is very important in regional anesthesia the operator should not try to recognize any landmarks until the patient has adopted the desired position. The patient is asked to lower the shoulder and flex the elbow, so the forearm rests on his/her lap. The wrist is supinated so the palm of the hand faces the patient’s face as shown in Figure 2B. This maneuver allows for detection of any subtle finger movement produced by nerve stimulation. If the patient cannot turn the wrist on supination a roll is placed under it so the fingers are free to move.
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Figure 2A: Patient positioning. The patient lies in a semi-sitting position with the head turned away from the side to be blocked. |
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Figure 2B: Patient positioning. The shoulder is down, the elbow is flexed and the palm of the hand rests on the patient’s lap while it is turned towards his face. |
The operator usually stands on the side to be blocked so for a left side block the palpation is done with the left hand and the needle is manipulated with the right, Figure 27-2b. For a right side block we teach exactly the opposite so the operator manipulates the needle with the left hand and palpates with the right. Otherwise, the operator may choose to manipulate the needle always with his/her favored hand regardless of which side block is being performed. This is easily accomplished by standing on one side of the head of the patient while reaching over to the other side when necessary.
With the patient in the described semi-sitting position and the shoulder down, the lateral (posterior) border of the SCM muscle is identified and followed distally to the point where it meets the clavicle. This particular point is marked on the skin over the clavicle, as shown in Figure 3. The lateral border of the SCM is usually clearly visible at the level where the external jugular vein crosses it. From this level the border can be traced caudally to the point where it meets the clavicle. A parasagital line (parallel to the midline) is drawn at this level to recognize an area at risk of pneumothorax risk medial to it. The point of needle entrance is found lateral to this parasagital plane separated by a distance we call “margin of safety”. This distance is about 1 in (2.5 cm) lateral to the insertion of the SCM in the clavicle or one “thumb breadth” lateral to the SCM as shown in Figure 4. The margin of safety can be alternatively established using a distance equal to the width of the clavicular head of the SCM at its insertion on the clavicle (16). The palpating index finger is placed at this site as shown in Figure 5. We customarily draw two arrows at this location pointing to each other. The proximal arrow, above the finger, is used to localize the needle entrance point, the distal one shows the direction of the needle path.
Figure 3: Landmarks. The lateral insertion of the SCM in the clavicle is marked.
Figure 4: Margin of safety. A distance of approximately 1 in (2.5cm) is measured laterally from the SCM, away from the pleural dome.
Figure 5: Point of needle entrance. The point of needle entrance is located just cephalad to the palpating finger and one fingerbreadth above the clavicle. The arrows on each side of the palpating finger help visualize the direction of the needle parallel to the midline.
The needle is inserted immediately cephalad to the palpating finger and advanced first perpendicularly to the skin for 2-5 mm (depending on the amount of subcutaneous tissue in the patient) and then turned caudally under the palpating finger to advance it in a direction that is parallel to the midline, as shown in Figure 6.
Figure 6: Needle direction. The needle is first introduced perpendicular to the skin and then is turned and advanced parallel to the midline in the direction of the arrows
The block should take place above the clavicle, under the palpating finger. As a goal we like to elicit an isolated muscle twitch in all fingers either in flexion or extension, often mistakenly referred as “median nerve” and “radial nerve” responses respectively (both nerves at this level are yet to be formed while their constituent fibers are traveling in all three trunks). Any other response carries a significantly lower success rate.
If reposition of the needle is necessary the needle is withdrawn and the penetration angle is adjusted in the anteroposterior plane, either slightly more posterior or slightly more anterior, but always parallel to the midline.
Modern nerve stimulators used in regional anesthesia are portable, accurate and easy to use. They should be checked periodically by the hospital engineering department to assure proper function and be fitted with new batteries according to a schedule. The ground electrode should be fresh out of the package. If for any reason it needs to be relocated is better to use a new one to avoid the increase impedance that comes with desiccation of the conductive gel. Its location in reference to the blocking site does not seem to have any significance. The negative electrode should be connected to the needle because less current is needed to produce a nerve response (17). However, with the modern nerve stimulator/needle settings this is not a problem because the needle could only be connected to the proper electrode. We always use a 5-cm, short-bevel, insulated needle to perform this technique.
We start the technique now with an intensity of around 0.8 mA and a pulse width of 100 µs. Once the desired response is obtained –that is a muscle twitch of the fingers that is clearly visible- we start the injection without reducing the nerve stimulator current. This is a unique characteristic of the supraclavicular block. In a recent study, the onset, duration and success rate with a supraclavicular block is unaffected by reducing the nerve stimulator to < 0.9 mA or less. (18) Supraclavicular and lumbar plexus blocks are only peripheral nerve blocks where injecting at a higher current than 0.5 mA is recommended.
Clinical pearls
To improve patient’s comfort, removal of a cast or splint is not necessary as long as the fingers are visualized.
The lateral border of the SCM muscle follows a straight line from the mastoid to the clavicle. Frequently a lateral deviation of this otherwise straight border can be seen in the proximity of the clavicle. This lateral extension should be disregarded as it usually represents the omohioid muscle. The true border can be found by prolonging the visible part of it straight distally into the clavicle.
The needle is inserted in a direction that is parallel to the midline. No other landmarks (e.g. nipples) should be used to direct the needle, as their position is highly variable.
Depending on the patient’s weight the palpating finger needs to exert different amounts of pressure on the deeper tissues. This maneuver helps bring the plexus closer to the skin and makes the trajectory of the needle shorter.
The needle should never be inserted deeper than 1 in (2.5 cm) if a twitch from the brachial plexus is not present. A twitch from one of the trunks on the other hand confirms the location of the needle in close proximity to the plexus, allowing for deeper introduction if necessary, in search of an appropriate twitch.
Because the trunks are contiguous, elicited twitches from one trunk follow the other without interruption. If the twitches instead disappear before reaching the lower trunk, the needle is withdrawn to the point of the previous twitch and advanced with a slight change in the anteroposterior angle of insertion.
The margin of safety of about 1 in (2.5 cm) lateral to the insertion of the SCM on the clavicle provides a safe distance lateral to the outer boundary of the pleural dome for the needle to travel. Because of the steep downward direction of the trunks, increasing this distance laterally may prevent the needle from contacting the plexus above the clavicle or miss the short trunks altogether.
In supraclavicular block an initial nerve stimulator current of 0.8 mA is strong enough to produce certain guidance into the plexus and small enough to guarantee sufficient proximity to it.
The risk of intraneural injection is minimized by using low injection pressures, meticulous technique and possibly by avoiding blocks in heavily sedated or anesthetized patients.
The injection is performed slowly with frequent aspirations while carefully observing the patient
If pain or abnormal pressure is felt at any point during injection, the needle should be withdrawn 1-2 mm after which a new assessment is made.
Traditionally the supraclavicular technique has not been considered an optimal choice for placement of catheters. The great mobility of the neck at this location carries a risk for catheter dislodgement. Tunelization of the catheter to the infraclavicular level could help to make the catheter more stable, however inadequate experience or data currently exists regarding this topic.
LOCAL ANESTHETIC CHOICES FOR SINGLE-SHOT AND CATHETER TECHNIQUES
Most of upper extremity surgeries performed under regional anesthesia last 1-3 hours. Consequently, we most commonly use 35-40 mL of 1.5% mepivacaine with 1:200,000 epinephrine, which provides about 3-4 hrs of anesthesia. Most hand surgeries including metacarpal and carpal fractures, radial and/or ulnar fractures as well as tendons and digital nerve repairs can be performed using this combination. The same anesthetic solution without epinephrine provides about 2-3 hrs of anesthesia. Usually 2mL of 8.4% sodium bicarbonate is added per every 20 mL of mepivacaine solution. Solutions of levobupivacaine, ropivacaine or bupivacaine provide longer acting anesthesia (5-7 hours) when required. For continuous techniques, a bolus dose of about 10-15 mL of local anesthetic solution can be given followed by an infusion rate of 8-10 mL/h. A solution of 0.2% levobupivacaine or similar can be used for this purpose. A patient-controlled analgesia (PCA) can be added to the system allowing the patient to administer 3-5 mL every 30 minutes for breakthrough pain. If PCA is added the basal infusion is decreased to around 5 mL/h. Breakthrough pain needs to be treated with a bolus of local anesthetic because simply increasing the rate of infusion could take several hours to have an effect.
The patients that receive single shot blocks can undergo surgery under intravenous sedation titrated to patient’s comfort. The sedation requirements vary from patient-to-patient and range from small intermittent boluses of midazolam and/or fentanyl to a propofol drip at 25- 50 mcg/kg/min or light general anesthesia.
Common side effects
associated with this technique include phrenic nerve block with
diaphragmatic paralysis and sympathetic nerve block with development
of Horner’s syndrome. They usually only require patient’s reassurance.
Phrenic nerve block reportedly occurs in about 50% of the time and is
not associated with respiratory dysfunction in healthy volunteers
(19). Complications similar to other peripheral blocks, such as
intravascular injection with development of systemic local anesthetic
toxicity, as well as hematoma formation may occur. Neuropraxia and
neurologic injury are similarly possible, but rarely reported.
The most feared complication of a supraclavicular block is
pneumothorax with rates quoted to be as high as 6.1%. As previously
mentioned, this number originates from a paper by Brand and Papper
published in 1961 (12). The authors compared 230 consecutive
supraclavicular blocks with 246 consecutive axillary blocks. However,
the comparison was neither blinded nor randomized and used several
different techniques. (7). In contrast, this complication is rare in
the modern literature (15). Our own experience with large number of
supraclavicular blocks was without any clinically manifested
pneumothorax.
It is frequently mentioned also that the pneumothorax complicating a
supraclavicular block has a delayed onset making routine postoperative
chest x-ray unjustifiable (20, 21). In fact the literature does
include such cases (1, 22). However most of the pneumothoraces
published in relationship to supraclavicular block have been usually
diagnosed within a few hours of the procedure and before patient’s
discharge.
Based on the available literature it can be said that pneumothorax associated with supraclavicular block is rare, often small, and is present within a few hours following the procedure. In some rare instances its presentation can be delayed up to 12 hrs. It is also important to emphasize that pneumothorax is a complication that for the most part is preventable with sound anatomical knowledge and meticulous technique as our experience demonstrates.
Supraclavicular block is a reliable, fast-onset and highly successful approach to bracial plexus anesthesia. The anatomy of the brachial plexus, with its three trunks confined to a much-reduced surface area offers an opportunity without parallel in the lower extremity or in any other part of the body for that matter. The block should be performed with the shoulder down. This maneuver places the trunks above the clavicle, so the block can be truly supraclavicular with the advantages already mentioned. Additionally, the potential risk of penetrating the first intercostal space is avoided. Inserting the needle at a distance lateral to the insertion of the SCM muscle in the clavicle and advancing it parallel to the patient’s midline keeps it away (lateral) from the pleural dome. Performing the block under the palpating finger also confers a great degree of control. Supraclavicular block should not be performed without a thorough knowledge of not only the brachial plexus but of the important surrounding structures as well. A combination of good anatomical knowledge, simple landmarks and meticulous technique can provide the operator with all the advantages of a truly remarkable block while significantly limiting its potential for complications.
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Moore D: Supraclavicular approach for block of the brachial plexus, in Moore D(ed): Regional block. A handbook for use in the clinical practice of medicine and surgery, 4th ed. Springfield, Charles C Thomas Publisher, 1981; pp 221-42
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Lanz E, Theiss D, Jankovic D: The extent of blockade following various techniques of brachial plexus block. Anesth Analg 62:55-8, 1983
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Urmey W: Upper extremity blocks, in Brown D (ed): Regional anesthesia and analgesia. Philadelphia, W.B. Saunders Company, 1996; pp 254-78
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Labat G: Regional anesthesia. Its technic and clinical application. Philadelphia, W.B. Saunders Company, 1922
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Patrick J: The technique of brachial plexus block anesthesia. Br J Surg 27:734-39, 1940
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Murphey D: Brachial plexus block anesthesia: an improved technic. Ann Surg 119:935-43, 1944
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Winnie A: Plexus anesthesia. Perivascular techniques of brachial plexus block. Philadelphia, W.B. Saunders Company, 1993
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Accardo N, Adriani J: Brachial plexus block: a simplified technic using the axillary route. South Med J 42:920, 1949
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Burnham P: Regional anesthesia of the great nerves of the upper arm. Anesthesiology 19:281-84, 1958
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De Jong R: Axillary block of the brachial plexus. Anesthesiology 22:215-25, 1961
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Brand L, Papper E: A comparison of supraclavicular and axillary techniques for brachial plexus blocks. Anesthesiology 22:226-29, 1961
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Winnie A, Collins V: The subclavian perivascular technique of brachial plexus anesthesia. Anesthesiology 25:353-63, 1964
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Brown DL, Cahill D, Bridenbaugh D: Supraclavicular nerve block: Anatomic analysis of a method to prevent pneumothorax. Anesth Analg 76:530-34, 1993
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Franco C, Vieira Z: 1,001 subclavian perivascular brachial plexus blocks: success with a nerve stimulator. Reg Anesth Pain Med 25:41-6, 2000
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Franco CD: The subclavian perivascular block. Tech Reg Anesth Pain Manag 3:212-16, 1999
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Hadzic A, Vloka J: Peripheral nerve blocks. Principles and practice. New York, McGraw-Hill, 2004
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Franco C, Domashevich V, Voronov G, et al: The supraclavicular block with a nerve stimulator: to decrease or not to decrease, that is the question. Anesth Analg 98:1167-71, 2004
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Neal J, Moore J, Kopacz D, et al: Quantitative analysis of respiratory, motor, and sensory function after supraclavicular block. Anesth Analg 86:1239-44, 1998
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Greengrass R, Steele S, Moretti G, et al: Peripheral nerve blocks, in Raj P (ed): Textbook of regional anestehsia. New York, Churchill Livingstone, 2002, pp 325-77
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