Guest Contributors

This essay is based on a project which has been in progress for about a decade. For those of you tired of reading about yet another technique in an area already overloaded with them, the paradigm upon which this is based is very different to the standard, textbook version. So it might be interesting. Can anything really be new or different? You can judge that for yourself, and for that you will have to read on.

I will try to limit myself to accepted definitions, peer-reviewed publications, and textbook references. A bibliography can be found at the end. It would obviously be more fun to fill this with my opinion, but if you are like me, that will irritate very quickly.

The technique itself is an exercise in applied anatomy, and applying anatomy. So isn’t every technique? Maybe - but I am not convinced that our grasp of anatomy is as sound as it could be, and I believe that this leads to errors in the way we approach our task. I hope to prove this in the following paragraphs. Does it matter? – I mean, if the block works, who cares? That is the point – there will be some success irrespective of anatomic knowledge/approach/technique, but to achieve reliability requires a different level of precision. Furthermore, if it is not 100% reliable, then we need to be able to troubleshoot, and if our model is faulty then at this stage the wheels start to fall off. Am I conceding some degree of failure? Yes, everybody fails occasionally – for a whole variety of reasons. I think it is more important to learn to manage the occasional failure on the basis of a high degree of initial success.

The ‘supraclavicular’ approach to the brachial plexus is the most effective technique BUT … it has a problematic complication profile :

pneumothorax
block of phrenic nerve
sympathetic chain
recurrent laryngeal nerve

Question: Is it possible to create a ‘supraclavicular’ technique WITHOUT that complication profile?

A lot of literature will tell you NO, and obviously I am going to say YES. But if I now give you a set of ‘how to do’ instructions, you are none the wiser. You won’t understand, and hence you can’t become reliable. Understanding this technique requires revisiting the basic foundations of regional anaesthesia in the area, and changing the paradigm. Then you will hardly need the instructions.

Why is a ‘supraclavicular’ technique so effective?

1. ‘Brachial plexus’ - an ‘interlacing network of nerves’ FORMED BY the nerve roots C5–T1, GIVING RISE TO the terminal nerves of the upper extremity. The terms ‘formed by’ and ‘giving rise to’ are exclusory, so what lies between them is the brachial plexus. The interlacing and interconnecting relationships of the plexus give us the trunks, divisions and cords.
2. The trunks, divisions and cords ( = brachial plexus) are located behind the middle third of the clavicle, where ‘supraclavicular’ techniques are based.
3. So the reason for efficacy of ‘supraclavicular’ techniques is simply that they anaesthetise the brachial plexus.

But doesn’t the ‘axillary sheath’ connect all the nerve elements into a continuum from neck to arm, permitting access to the plexus at multiple levels, & therefore we can modify complication profile simply by putting our needle at a different place ?

To answer this, let’s examine some of these terms :

1. ‘Axillary ’:


1. The ‘axilla’ is an anatomic compartment with 4 sides, an apex and a base.
2. The armpit is not the axilla - it is the base of the axilla.
3. The neck is not part of the axilla.
4. The apex of the axilla, formed by the intersection of first rib, clavicle and scapula, is represented on the skin surface by the supraclavicular fossa. This is where we put ‘supraclavicular’ blocks. We could equally call them ‘apical axillary’ blocks.
5. As stated above, the base of the axilla is what we often refer to as the armpit, and this is where we put ‘axillary’ blocks. We could call them ‘basal axillary’ blocks.
6. The anterior wall of the axilla, formed by the pectoral muscles and the clavicle, is where we put ‘infraclavicular blocks’, or alternatively ‘anterior axillary’ blocks.
7. The difference between a ‘basal axillary’ block and an ‘apical axillary’ block is in the nerves which we find at each site – the brachial plexus at the apex and terminal nerves (radial, median, ulnar) at the base.
8. The interscalene block aims at nerve roots C5-6. By definition then it is not a brachial plexus block. Because it pierces the prevertebral fascia and puts local anaesthetic between the anterior and middle scalene muscles (lateral vertebral muscles), it is a paravertebral technique.
9. You will immediately appreciate a problem with our standard nomenclature.

2. ‘ Sheath ’:


1. The ‘sheath’ is a fictional notion. Big statement – read on.
2. In the neck, the prevertebral lamina of the cervical fascia covers the scalene muscles, forming the floor of the posterior triangle.
3. The scalene muscles are classified as lateral vertebral muscles.
4. All the regional techniques in the neck area (interscalene & modifications, deep cervical plexus, subclavian perivascular, intersternocleidomastoid) pierce the prevertebral fascia, are largely contained by it, & hence are paravertebral techniques.
5. In the axilla, the neurovascular bundle is enclosed in a series of relatively fragile tissue planes, closely surrounded by rigid/semirigid anatomy which creates the ‘axillary tunnel’. The axillary tunnel is largely responsible for containing/directing the injected solution.
6. There is connection & continuity between the tissue planes of the axillary tunnel & the prevertebral fascia, but spread between areas depends upon variable interconnections between these soft tissues, & the variable dimensions of the axillary tunnel.
7. So far better to deliver the local anaesthetic to exactly where you want it, than to rely upon spread along an unpredictable pathway.

3. ‘ Permitting access to the plexus at multiple levels ’:


1. In fact, the clinical profiles at different sites (interscalene, supraclavicular/ infraclavicular, axillary – to use familiar terms) are widely accepted as being different.
2. This is because these different sites are anatomically different.
3. The plexus can be accessed readily at one of these levels.

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1. ‘Bending’ the needle – why bend the needle ? Doesn’t that weaken it ? Isn’t it being too complicated ? : a. This is not the first time in anaesthesia that placing a bend in a needle has been employed – it is often useful to improve the angle of attack when placing an intravenous cannula. b. Needles don’t break with a single, restricted bend. c. Do we allow the anatomy to control us by the limitations of our equipment ? A simple bend in the shaft of a needle to facilitate manoeuvring in a restricted area is hardly complicated – to achieve precision is a different story.


2. The risk of pneumothorax: if the tip of a needle is placed in the supraclavicular fossa (ie apex of axilla), it will most likely be pointing towards the lung, hence potentially threatening it. The challenge is to change that relationship, ie make the needle not point towards the lung. Now if the needle can be guided into a tangential relationship to the chest wall, it doesn’t point towards the lung and hence cannot penetrate it (Anaesth Int Care 2000;28:676-9 has an illustration of this). Using a straight needle, with the neck on one side and the clavicle on the other, it is difficult if not impossible to achieve that particular relationship – but it is easy to do it if the needle has a bend in it. The needle tip can be guided into that low risk position. This is one part of minimizing the risk of pneumothorax.



A tangent to the chest wall




3. If we know how deep the nerves are, and how deep the lung is, then we know how far we can and cannot go. This is the principle behind ‘depth-gauging’. In the lateral supraclavicular fossa, the plexus lies posterior to the clavicle just as the arterial pulsation becomes obscured by the clavicle. This relationship can be manipulated by simple geometry to give us the depth estimates. See the paper in Anesthesia & Analgesia, referenced at the end, for further details.
4. Combine the ‘bend’ with ‘depth-gauging’ and the risk of pneumothorax is minimal/negligible.


5. Bend the shaft of the needle a small amount (30°), 1-2 cm from the tip of the needle (plexus < 1 cm deep, bend at 1 cm; plexus > 1 cm deep, bend at 2 cm), and advance the needle safely up to the bend through the superficial tissues without threatening the lung. Once the bend is reached, gradually redirect the needle tip laterally as it is further advanced so that it is no longer pointing towards the lung as it approaches the plexus.


6. The rest of the complication profile: if the hub of the needle is brought in beside the neck, then at the other end of the needle the needle tip becomes more closely aligned with the plexus. It also places the needle tip far enough away from the medially located phrenic and other nerves to avoid them. Again, not possible to do with a straight needle.


7. Other reasons to bend a needle? – catheter placement for continuous analgesia or anaesthesia is easy, since we are aligned with the nerves.

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1. I do these blocks with the patient semirecumbent.


2. This levels the supraclavicular fossa and the first rib.


3. This orients the axilla for me.


4. It also gives me a flat working surface, and a comfortable position to work from.

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This was mentioned earlier, and the scientific work related to it was presented at XXIII Annual ESRA Congress Greece 2004. Publication is in progress but in the meantime, a little more information might be of interest:

A. The ‘Outside Properties’ of the Axillary Tunnel:


1. The rigid walls of the axillary tunnel are not straight and even throughout – there are 2 points where the dimensions narrow, forming points of resistance. These occur at the apex of the axilla and just lateral to the coracoid process. The spread of an injection will be affected by where the injection occurs relative to these points – injecting on either side tends to restrict flow to the side of injection, whereas within the point of resistance sees even spread either side.

B. The ‘Inside Properties’ of the Axillary Tunnel:


1. The tissue planes within which the neurovascular bundle runs also determine spread of local anaesthetic. Injecting on the outside of the bundle does not guarantee spread across the bundle, whereas injecting in the centre of the bundle provides more certainty of even spread.
2. In some patients, the tissue planes restrict flow and give rise to patchy blocks. This is compartmentalisation. Aiming for the nerve you want seems the best way to control for this phenomenon.

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If this has been of interest it will be worthwhile chasing up the references at the end. The following pictures will provide some more clues as to how this technique works.

I use it for all upper extremity work. Separate skin cover is required for shoulders with subcutaneous local anaesthetic in the supraclavicular fossa. You do need to get the right twitch for the different territories – superior trunk/posterior cord for shoulders, finger twitches for everything else.

Surgery on bones usually buys a catheter – if you don’t believe these procedures are painful, wait until its your turn. It is worth persevering through the learning curve – remember, fundamentally one technique to get you everything. Good luck, my e-mail is philip.cornish@nmhs.govt.nz if you have any queries.

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	Positioning
	Marking the Artery
	Depth Gauging
	Ready to Insert – View from the front
	Ready to Insert – View from the side
	Inserting beyond the bend
	Cannula Sited, Needle Withdrawal
	Cannula in situ
	Catheter-through-cannula
	Withdrawing cannula over catheter
	Cannula Withdrawal
	Brachial Catheter secured

Books

1. Churchills Medical Dictionary


2. Essentials of Human Anatomy. Ed. Woodburne

Journal Articles:

1. Lanz EL, Theiss D, Jankovic D. The extent of blockade following various techniques of brachial plexus block. Anesth Analg 1983;62:55-58


2. Cornish PB, Greenfield LJ: Brachial plexus anatomy. Reg Anesth. 1997 Jan-Feb; 22[1]:106-7


3. Cornish PB. Regarding axillary and supraclavicular techniques of nerve blocks being described as approaches to brachial plexus. Reg Anesth Pain Med 1998 Jan-Feb;23:109-10


4. Cornish PB, Greenfield LJ, O'Reilly M, Allan L : Indirect vs direct measurement of brachial plexus depth. Anesth Analg 1999 May;88[5]:1113-6
   
5. Cornish PB : Supraclavicular Regional Anaesthesia Revisited. Anaesth Int Care 2000;28:676-9


6. Cornish PB, Nowitz M. ‘A Magnetic Resonance Imaging Analysis of the Infraclavicular Region – Can Brachial Plexus Depth Be Estimated Prior To Needle Insertion? In Press Anesth Analg

Abstracts:

1. Cornish PB, Nowitz M: A Comparison of Bent vs Straight Needles for Supraclavicular Brachial Plexus Anaesthesia. IMRAPT 2002; 14(2): 114


2. Cornish PB, Nowitz M, Brunberg J: An Analysis of the Spatial Relationships of the Brachial Plexus Using Magnetic Resonance Imaging. IMRAPT 2002; 14(2): 116


3. Cornish PB, Mowitz M: Can plexus depth be estimated? An anatomic analysis related to the vertical infraclavicular brachial plexus block (VIB) using magnetic resonance imaging (MRI). Reg Anesth & Pain Medicine, 28, no.5, 2003:p 10.


4. Cornish PB, Leaper C, Nelson G, Anstis F, McQuillan C, Stienstra R Can Phrenic Nerve Paresis Be Consistently Avoided During Continuous Supraclavicular Regional Anaesthesia? RAPM 2004 September Supplement


5. Cornish PB, Leaper CJ: The Axillary Tunnel – Redefining the Limits of Spread for Brachial Plexus Blockade. RAPM 2004 September Supplement


6. Cornish PB, Leaper CJ, Nelson G. Continuous Bilateral Supraclavicular Regional Anaesthesia Without Phrenic Nerve Palsy – Extending the Options. RAPM 2004 September Supplement


7. Cornish PB, Leaper C, JL Hahn Evaluation of Spread of a Bolus Injection Administered via a Brachial Catheter Using Contrast-Enhanced Computerised Axial Tomography (CECT) Scanning. RAPM 2004 September Supplement


8. Cornish PB: The ‘Sheath’ of the Brachial Plexus – Fact or Fiction? RAPM 2004 September Supplement

© pbcornish2005

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