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Ultrasound Guided Nerve Block

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Illustration 1: Supraclavicular block distribution .

Illustration 2: Course of the Brachial Plexus

Figure 1: Hand placement for the supraclavicular block.

Figure 2: Image of the brachial plexus in the supraclavicular fossa.

Figure 3:  In-plane needle placement.

Video  1: Supraclavicular Block

Figure 4: Effect of probe tilting on plexus appearance.

Figure 5: Effect of probe tilting on plexus appearance.

Figure 6: Finding the Corner Pocket.

Video 2: Supraclavicular Block Starting in the Corner Pocket.

 

Leonard V. Bunting, M.D.

Supraclavicular Brachial Plexus Block

Introduction
In experienced hands, the supraclavicular brachial plexus block provides dense anesthesia to the upper arm, elbow and forearm. The superficial placement of the plexus at this site leads to good sonographic visualization and a quick procedure that is well tolerated by patients in the ED or operating room. (1-3) Although dense anesthesia at the shoulder can occur with this block, anesthesia at the shoulder is more reliably achieved using the interscalene block.

Illustration 1: Supraclavicular block distribution.


Anatomy
The supraclavicular fossa is a triangular depression on the lateral neck bounded medially by the sternoclaidemastoid muscle (SCM), inferiorly by the clavicle and superiorly by the trapezius muscle. (4) The brachial plexus enters the supraclavicular fossa after exiting the interscalene space and turning laterally to run on the superior-posterior aspect of the subclavian artery. The plexus courses infero-laterally through the fossa with the subclavian artery. At the midclavicle, the plexus and artery pass inferior to the clavicle and superior-lateral to the first rib as they exit the fossa. (5) Inferior to the artery and medial to the first rib is the dome of the lung, leading to the possibility of injury during the block.



Illustration 2: Course of the Brachial Plexus.

Scanning Technique
The patient may be positioned anywhere from recumbent to sitting upright with their head rotated away from the block site. ( Patient and Room Setup) A high frequency (10-18 MHz), linear array probe is used for this block. The probe is placed in the supraclavicular fossa and oriented perpendicular to the subclavian artery with the probe indicator oriented towards the clavicle for a left-sided block (Figure 1) and the trapezius for a right-sided block.

Figure 1: Hand placement for the supraclavicular block.

The subclavian artery is identified by its thick wall and brisk pulsations. Color-flow is rarely needed but should be used to clarify anatomy if needed. The subclavian vein is infero-medial and not always visualized. Immediately superior and postero-lateral to the artery, the brachial plexus is seen as a grouping of small hyperechoic circles with hypoechoic centers, similar to a bunch of grapes (Figure 2). Alternatively, the plexus can be found in the interscalene space and followed distally to its association with the subclavian artery. Deep to the artery the structures of note are the dome of the lung (identified by its characteristic movement and scatter) and the first rib (identified by its hyperechoic surface with dense posterior shadowing).

Figure 2: Image of the brachial plexus in the supraclavicular fossa.

Nerve Block
An in-plane, posterior approach (In-Plane vs. Out-Of Plane Approach) will be described (Figure 3). After the appropriate equipment is setup (Anesthetic, Needle type and Sterile Prep.), the skin is anesthetized and the block needle is inserted about 1 cm into the skin using either a medial-to-lateral or lateral-to-medial orientation. The needle tip is located and followed throughout the procedure (Needle Tip).

Figure 3:  In-plane needle placement.

Being careful to avoid any sensitive structures, the needle is slowly advanced towards the deep border of the plexus where it meets the subclavian artery. Once careful movement of the needle causes movement on the plexus, injection may begin. (Injection Precautions) Appropriate needle placement is confirmed sonographically by spread of anesthetic around the entire plexus and dissecting the plexus from the artery away, often moving it towards the needle. The medial-to-lateral approach is believed to reduce the risk of pleural puncture, especially when the needle tip is poorly visualized. Both techniques however seem to have similar success and complication rates. (3) Readjustment of the needle position may be necessary to achieve adequate distribution of anesthetic. Typical block volumes are 30 - 40 ml (6). Patients and staff should be appropriately educated regarding the block. (Post-Block Care).

Video  1: Supraclavicular Block.


Pearls and Pitfalls
The brachial plexus in the supraclavicular fossa does not travel parallel to the skin surface. Therefore it may be necessary to alter the probe’s angle to the skin to optimally visualize the plexus (‘fanning the probe’, Figures 4 and 5).

Figures 4 and 5: Effect of probe tilting on plexus appearance.



A popular initial target for injection is the area inferio-medial to the plexus, postero-lateral to the subclavian artery and superior to the first rib, commonly referred to as ‘the corner pocket’ (Figure 6). Although an easy initial target, one study found an unacceptably high-rate of ulnar sparing using this approach. (7) Therefore, regardless of the initial needle placement, it is recommended that the needle be redirected as needed to ensure the entire plexus is surrounded by local anesthetic.

Figure 6: Finding the Corner Pocket.

Video 2: Supraclavicular Block Starting in the Corner Pocket.

This approach has three additional complications that should be noted. First, although the phrenic nerve is much further from the block site than in the interscalene approach, ipsilateral diaphragm paralysis still occurs in up to 50% of cases due to proximal spread of the LA, but seems rarely symptomatic. (8,9) Minimizing the amount of LA used may decrease the likelihood of this complication. (10) Second, the proximity of the lung makes a pneumothorax possible. In large case series, no symptomatic pneumothoraces occurred (8,3), but individual cases have been reported. (11) Finally, a temporary Horner’s syndrome may result from proximal LA spread and blockage of sympathetic afferents. (8) This is self-limited and will resolve as the block resolves.

References

1. Stone MB, Wang R, Price DD.
Ultrasound-guided supraclavicular brachial plexus nerve block vs procedural sedation for the treatment of upper extremity emergencies. Am J Emerg Med. 2008;26(6):706-10.

2. Stone MB, Price DD, Wang R.
Ultrasound-guided supraclavicular block for the treatment of upper extremity fractures, dislocations, and abscesses in the ED. Am J Emerg Med. 2007;25(4):472-5.

3. Perlas A, Lobo G, Lo N, Brull R, Chan VW, Karkhanis R.
Ultrasound-guided supraclavicular block: outcome of 510 consecutive cases.  Reg Anesth Pain Med. 2009;34(2):171-6.

4. Wikipedia.
Supraclavicular fossa. [Accessed April 12th 2011].

5.  Franco C.
Supraclavicular Brachial Plexus Block. In Hadzic A (ed): Textbook of Regional Anesthesia. McGraw-Hill, 2007, p 420-21.

6 .  Duggan E, El Beheiry H, Perlas A, Lupu M, Nuica A, Chan VW, Brull R.
Minimum effective volume of local anesthetic for ultrasound-guided supraclavicular brachial plexus block. Reg Anesth Pain Med, 2009;34:215-8.

7. Fredrickson MJ, Patel A, Young S, Chinchanwala S.
Speed of onset of corner pocket supraclavicular' and infraclavicular ultrasound guided brachial plexus block: a randomised observer-blinded comparison.  Anaesthesia. 2009;64(7):738-44.

8. Franco C.
Supraclavicular Brachial Plexus Block. In Hadzic A (ed): Textbook of Regional Anesthesia. McGraw-Hill, 2007, p 424.

9. Riazi S, Carmichael N, Awad I, Holtby RM, McCartney CJ.
Effect of local anesthesia volume on the efficacy and respiratory consequences of ultrasound-guided interscalene brachial plexus block. Br J Anes, 2008; 101: 549-56.

10. Jeon DG, Kim WI.
Cases series: ultrasound-guided supraclavicular block in 105 patients. Korean J Anesthesiol. 2010;58:267-71.

11. Bhatia A, Lai J, Chan VW, Brull R.
Case report: pneumothorax as a complication of the ultrasound-guided supraclavicular approach for brachial pexus block. Anesth Analg, 2010; 111: 817-9.

 

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