ELI5: Interscalene Block vs Supraclavicular Block

[ms420]

Because I have expressed interest in anesthesia, they are letting me follow the block team around. I'm learning a lot, but I'm not able to put anything into perspective, especially when I'm hearing different things from different attendings and fellows.

One guy I work with says the suprclavicular block is the spinal of the upper extremity.

Another guy says the Interscalene Block is better for the shoulder, and because it blocks the three trunks of the brachial plexus, it gets everything that the supraclavicular block can hope for, and then some.

I'm not smart (or experienced) to know who's right. (And I'm not about to correct either of my superiors.) But the Interscalene Guy did ask me to make the case for the Supraclavicular Block.

If the interscalene block deposits anesthetic at the level of the trunks (C5-T1), then why isn't that better than placing local anesthetic more distally, where the brachial plexus may have become five or six divisions, or more distally still (axillary block), where we are trying to identify specific branches?

Interscalene Guy is a big fan of Einstein's logic that if you can't explain something to the level of a six-year old, then you don't understand it yourself. (I'm a fan of Reddit, who has a whole subreddit (ELI5: Explain Like I'm Five) that borrows Einstein's logic.)

I don't know enough to know why Interscalene Guy is wrong. The "spinal of the upper extremity" ought to be placing local anesthetic as close to the spinal cord as possible. Or, so it seems to me.

Can anybody put it in simple terms for me? (And, yes, I've searched, and express my thanks to BladeMDA for Best Upper Extremity Block under U/S and everybody who contributed to Distal radius and proximal humerus fractures .)

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[Hoya11]

The Brachial plexus covers C5 - T1 true.

But not all levels have an equal mix of the fibers.

Meaning that at the interscalene level, your going to have more fibers of C5,6,7 than C8 and T1

And at the Supraclavicular level, your going to have more fibers of C7,8,T1 than you do at the interscalene level.

Therefore, Interscalene is better for shoulder which has innervation from the fibers higher up in the UE.

Supraclavicular is better for Elbow and Hand as it contains more of the fibers for lower down in the UE.

Of course this is a generalization, and it IS possible to cover the whole hand sometimes with an interscalene.

However, if you routinely do Interscalene level blocks for a hand surgery, you WILL indeed have some failures more often than with the SC block.

Similarly, if you routinely do Supraclaviculars for shoulder surgery, you will have a numb arm below the surgery but pain in the shoulder more often than with the IS block

 

[Lidolover]

The way I have simplified it to my mind is that interscalene covers the suprascapular nerve (that takes of really early and innervates 70% of the shoulder) whereas Supraclavicular does not. Hence, you prefer interscalene for shoulder and supraclavicular for below the shoulder. The reason is the risk of phrenic nerve paresis is significantly higher with interscalene and there is not reason to put the patient in that risk unless you are doing shoulder surgery. Even in that case, If pt has copd or other resp issues that could declare themselves even more in the setting of phrenic paresis you go with supraclavicular or infraclavicular supplemented by separate suprascapular nerve block. There is also the option of low trunk low volume block That is a modified interscalene (u actually go lower and admin less local).

 

[ms420]

Thanks, Lidolover. That makes sense: there's no reason to pick up the suprascapular nerve (and risk phrenic involvement) unless the surgery is at the shoulder.

Does that mean that coverage below the shoulder (elbow, forearm, wrist, and hand) is the same with interscalene and supraclavicular?

If it were up to me, I'd call the Interscalene the "unilateral spinal of the upper extremity," and then call the supraclavicular block the "3-in-1" or "combined femoral/sciatic" of the upper extremity (good for thigh, knee, and below, but not good for hip surgery). Obviously, I'm wrong about something, or other people would be using that terminology.

 

[leaverus]

if it were up to me, i'd call the interscalene the "interscalene of the upper extremity" and the supraclavicular the "supraclavicular of the UE."

 

[deleted162650]

Does that mean that coverage below the shoulder (elbow, forearm, wrist, and hand) is the same with interscalene and supraclavicular?

No. Interscalene commonly spares the ulnar making it a poor choice for surgery of the distal UE.

See Hoya’s response above.

 

[ms420]

Why is the ulnar nerve spared?

I'm clearly thinking about this incorrectly, but it seems to me the closer you are to the spinal cord, the better chance you have of obtaining a complete block of all the nerves. What's the simple clinical pearl that I'm missing?

The needle descends on the brachial plexus from the cranial aspect in both blocks, so it's not like "approaching from above" or "approaching from below" can explain a difference between C5 and T1 involvement. Everybody seems to think that 20-30 cc counts as a "high volume" of local anesthetic, so nobody is making the argument that only the superficial fibers of the cord, root, or division are blocked, leaving the innermost nerve fibers unblocked.

If going farther away from the central cord is better (for distal surgeries), then should I believe that the infraclavicular block is even better than the supraclavicular, and the axillary block is better than them all. (FWIW, locally, the notion seems to be that "axillary blocks are the vertical c/s incision of regional blocks. You should probably know about them; and what you need to know is that nobody does them.") I'm no expert, but outside of motor sparing effects of the adductor canal block, nobody acts like it is superior to the femoral nerve block, nor that the femoral nerve block is better than lumbar plexus or spinal.

But, it does seem to be the case that the supraclavicular is considered better than the interscalene. And there should be a reason for it explainable to a six-year old, let alone a MS4.

 

[deleted162650]

When you perform an Interscalene, you are primarily targeting the C5-6-7 nerve roots as they enter the brachial plexus (those are what make up the “snowman” on U/S). With enough volume, there is an ok chance that you get enough spread to also block C8-T1, but it’s not guaranteed. You need to open Netter and review the brachial plexus in relation to where each of these three blocks is performed.

 

[deleted162650]

Oh, and from this point forward I would stop listening to anything the “pro-Interscalene” guy says.

 

[DocVapor]

Also I just graduated residency and I love the axillary block. Sounds like your place is one of those where when you keep asking questions the answer always becomes "Because that's the XXXX way."

 

[Urzuz]

FWIW, locally, the notion seems to be that "axillary blocks are the vertical c/s incision of regional blocks. You should probably know about them; and what you need to know is that nobody does them."

The locals you’re learning from are idiots. Disregard everything they say.

 

[secretasianman]

You are thinking in terms of absolutes and it’s tripping you up. Only a sith deals with absolutes. Is the whole plane contiguous, or not?

 

[ethilo]

C7-T1 enter the interscalene groove way more distally and lower / more caudal. As a result you commonly get "ulnar sparing" with the interscalene block because your local anesthetic just doesn't reach those spinal nerves - it only primarily affects the C5-6 nerve roots. Supraclavicular is an injection at the divisions beyond the interscalene groove, where the entirety of the brachial plexus is present. So you won't get ulnar sparing there since it's a location where C7-T1 actually course through.

 

[deleted697535]

Tell em most ppl think regional is bullsh1t, see a bunch of something thats probably nerves and hopefully not vessels then shove a big needle into it blast 20mls of whatever the tech drew up and move on with their day...
Ulnar sparing just means not enough propofol given

 

[C4C]

How's this for a simple explanation:

It's a little bit like you are wiring your home theater with 7.1 speakers. Coming out of your amplifier, you will have a mess of wires going to the right three speakers and the left three speakers. It is much easier to thread that wire bundle through the walls in your home theater if you ziptie them to make them the three wires move as one, right?

Now let's say a bad actor wants to cut the sound to the right side of the room. (Yes, he could take out the amplifier. That would take out all the speakers, though--not just the left and right. Depending on how far you want to carry this analogy, that could be something like a true spinal block.)

He could cut the wires individually as they come out of the rear of the amplifier...but that would mean he has to make three cuts.

Or, he could make a simple snip anywhere after the zip tie, where all the speaker wires are bundled together "as one."

The brachial plexus forms one "wire bundle," but if you block it before the bundle is tightly packed, you are likely miss some of the nerves that will eventually form the plexus. That's what happens on some interscalene blocks, especially those placed high in the neck. If you consider that C5, C6, C7, C8, and T1 are five levels, spanning at least 5cm as they leave the spinal cord, then you will see that is a large distance you are asking your local anesthetic to spread.

I've included a rough picture that I've doodled on. Thanks to NYSORA for the original. I hope it makes things clear. The picture of the dissection is taken from a vantage point much lower than where we place our blocks, which makes the plexus seem to sit even farther below (caudal to) the clavicle than in reality. The "clinical pearl" you seek is that somewhere near where the plexus goes from above the subclavian artery to below it is where it is most tightly packed (to say nothing of nearest to the skin). That's why the supraclavicular approach, in most practioners' hands, offers more reliable neural blockade.

By the way, I consider an interscalene block to be a supraclavicular block, inasmuch as it is above the clavicle. And since the scalene muscles attach to the first rib somewhere near the middle third of the clavicle, I have a very easy time writing my notes to say only that I visualized the brachial plexus in the area superior to the middle third of the clavicle. I don't bother trying to distinguish between interscalene and supraclavicular. I bill it as a brachial plexus block and leave it at that. (True, I try to keep in mind where the suprascapularis nerve is likely to peel away from the plexus when I am blocking for shoulders, but I don't get real excited trying to make huge functional distinctions between the two.)

And, not that it matters, but I haven't performed (or seen performed) an axillary block since residency 15+ years ago. In that time I also haven't used (or, for that matter, seen used) a Mac blade (in our training program, a common refrain was that "people who intubate for a living use Miller blades")--but I wouldn't say that either axillary blocks or Mac blades are necessarily out-of-fashion.

I would try to encourage you not to see any single approach as "right" or "wrong," or even necessarily "always better" or "always worse." Especially during your education and training, take opportunity to try to skin a cat as many ways as you can.

 

[anbuitachi]

How's this for a simple explanation:

It's a little bit like you are wiring your home theater with 7.1 speakers. Coming out of your amplifier, you will have a mess of wires going to the right three speakers and the left three speakers. It is much easier to thread that wire bundle through the walls in your home theater if you ziptie them to make them the three wires move as one, right?

Now let's say a bad actor wants to cut the sound to the right side of the room. (Yes, he could take out the amplifier. That would take out all the speakers, though--not just the left and right. Depending on how far you want to carry this analogy, that could be something like a true spinal block.)

He could cut the wires individually as they come out of the rear of the amplifier...but that would mean he has to make three cuts.

Or, he could make a simple snip anywhere after the zip tie, where all the speaker wires are bundled together "as one."

The brachial plexus forms one "wire bundle," but if you block it before the bundle is tightly packed, you are likely miss some of the nerves that will eventually form the plexus. That's what happens on some interscalene blocks, especially those placed high in the neck. If you consider that C5, C6, C7, C8, and T1 are five levels, spanning at least 5cm as they leave the spinal cord, then you will see that is a large distance you are asking your local anesthetic to spread.

I've included a rough picture that I've doodled on. Thanks to NYSORA for the original. I hope it makes things clear. The picture of the dissection is taken from a vantage point much lower than where we place our blocks, which makes the plexus seem to sit even farther below (caudal to) the clavicle than in reality. The "clinical pearl" you seek is that somewhere near where the plexus goes from above the subclavian artery to below it is where it is most tightly packed (to say nothing of nearest to the skin). That's why the supraclavicular approach, in most practioners' hands, offers more reliable neural blockade.

By the way, I consider an interscalene block to be a supraclavicular block, inasmuch as it is above the clavicle. And since the scalene muscles attach to the first rib somewhere near the middle third of the clavicle, I have a very easy time writing my notes to say only that I visualized the brachial plexus in the area superior to the middle third of the clavicle. I don't bother trying to distinguish between interscalene and supraclavicular. I bill it as a brachial plexus block and leave it at that. (True, I try to keep in mind where the suprascapularis nerve is likely to peel away from the plexus when I am blocking for shoulders, but I don't get real excited trying to make huge functional distinctions between the two.)

And, not that it matters, but I haven't performed (or seen performed) an axillary block since residency 15+ years ago. In that time I also haven't used (or, for that matter, seen used) a Mac blade (in our training program, a common refrain was that "people who intubate for a living use Miller blades")--but I wouldn't say that either axillary blocks or Mac blades are necessarily out-of-fashion.

I would try to encourage you not to see any single approach as "right" or "wrong," or even necessarily "always better" or "always worse." Especially during your education and training, take opportunity to try to skin a cat as many ways as you can.

"And, not that it matters, but I haven't performed (or seen performed) an axillary block since residency 15+ years ago. In that time I also haven't used (or, for that matter, seen used) a Mac blade (in our training program, a common refrain was that "people who intubate for a living use Miller blades")--but I wouldn't say that either axillary blocks or Mac blades are necessarily out-of-fashion."

whut?

mac blades are the go to blades. who intubates a coding patient getting cpr with miller blades? are you doing retromolar intubations with your millers???

 

[Southpaw]

@C4C have you not used a glidescope? That’s a mac blade.

 

[anaesthetic]

.

 

[deleted162650]

This is what I was taught during residency as well. Imagine my surprise when I got to fellowship, and absolutely nobody was doing interscalene blocks for shoulder surgery. Instead, they did pre-op supraclavicular blocks +/- post-op superficial cervical blocks if needed, and the patients actually did very well in PACU. They also did anterior suprascapular nerve blocks occasionally, which I'm less familiar with. "Science" is indeed fleeting. See below:

"Comparison Between Ultrasound-Guided Supraclavicular and Interscalene Brachial Plexus Blocks in Patients Undergoing Arthroscopic Shoulder Surgery"

Comparison Between Ultrasound-Guided Supraclavicular and Interscalene Brachial Plexus Blocks in Patients Undergoing Arthroscopic Shoulder Surgery: A Prospective, Randomized, Parallel Study

Although supraclavicular brachial plexus block (SCBPB) was repopularized by the introduction of ultrasound, its usefulness in shoulder surgery has not been widely reported. The objective of this study was to compare motor and sensory blockades, the incidence ...

www.ncbi.nlm.nih.gov

"Comparison of Anterior Suprascapular, Supraclavicular, and Interscalene Nerve Block Approaches for Major Outpatient Arthroscopic Shoulder Surgery: A Randomized, Double-blind, Noninferiority Trial"

Comparison of Anterior Suprascapular, Supraclavicular, and Interscalene Nerve Block Approaches for Major Outpatient Arthroscopic Shoulder Surgery: A Randomized, Double-blind, Noninferiority Trial

This study suggests that anterior suprascapular block provides noninferior analgesia compared to interscalene block, and better preserves vital capacity. While supraclavicular block was associated with some vital capacity preservation compared to interscalene block, the analgesia provided by...

anesthesiology.pubs.asahq.org

An U/S guided ISB and SCB are literally about 2cm away from each other. With 20-30mLs of local I’m not surprised that results are damn near equivalent.

Another thing to note, is that “ulnar sparing” is possible with SCB if you fail to get local down into the “corner pocket”.

 

[anbuitachi]

This is what I was taught during residency as well. Imagine my surprise when I got to fellowship, and absolutely nobody was doing interscalene blocks for shoulder surgery. Instead, they did pre-op supraclavicular blocks +/- post-op superficial cervical blocks if needed, and the patients actually did very well in PACU. They also did anterior suprascapular nerve blocks occasionally, which I'm less familiar with. "Science" is indeed fleeting. See below:

"Comparison Between Ultrasound-Guided Supraclavicular and Interscalene Brachial Plexus Blocks in Patients Undergoing Arthroscopic Shoulder Surgery"

Comparison Between Ultrasound-Guided Supraclavicular and Interscalene Brachial Plexus Blocks in Patients Undergoing Arthroscopic Shoulder Surgery: A Prospective, Randomized, Parallel Study

Although supraclavicular brachial plexus block (SCBPB) was repopularized by the introduction of ultrasound, its usefulness in shoulder surgery has not been widely reported. The objective of this study was to compare motor and sensory blockades, the incidence ...

www.ncbi.nlm.nih.gov

"Comparison of Anterior Suprascapular, Supraclavicular, and Interscalene Nerve Block Approaches for Major Outpatient Arthroscopic Shoulder Surgery: A Randomized, Double-blind, Noninferiority Trial"

Comparison of Anterior Suprascapular, Supraclavicular, and Interscalene Nerve Block Approaches for Major Outpatient Arthroscopic Shoulder Surgery: A Randomized, Double-blind, Noninferiority Trial

This study suggests that anterior suprascapular block provides noninferior analgesia compared to interscalene block, and better preserves vital capacity. While supraclavicular block was associated with some vital capacity preservation compared to interscalene block, the analgesia provided by...

anesthesiology.pubs.asahq.org

why are they doing 1-3 blocks for shoulder surgery, when they can just do 1???

 

[Sonny Crocket]

An U/S guided ISB and SCB are literally about 2cm away from each other. With 20-30mLs of local I’m not surprised that results are damn near equivalent.

Another thing to note, is that “ulnar sparing” is possible with SCB if you fail to get local down into the “corner pocket”.

Yo dawg. You gotta get dat corner pocket if you want dat ulnar nerve. Agree.

 

[deleted162650]

Yo dawg. You gotta get dat corner pocket if you want dat ulnar nerve. Agree.

That's racist man. Not cool.

 

[deleted875186]

I will also say that you should aim to block as little of the arm that is needed for surgery. Many patients hate having a completely numb arm. If it weren’t for the fact that the axillary block wears off faster than a supraclav, I would prefer to do it for any type of hand surgery.

 

[deleted162650]

I will also say that you should aim to block as little of the arm that is needed for surgery. Many patients hate having a completely numb arm. If it weren’t for the fact that the axillary block wears off faster than a supraclav, I would prefer to do it for any type of hand surgery.

Do an Infraclav then. Spares the shoulder and allows you to target cords if that's your thing.

 

[Urzuz]

If it weren’t for the fact that the axillary block wears off faster than a supraclav, I would prefer to do it for any type of hand surgery.

If the same concentration, volume, and adjuvants are used, how significant is the difference in length of blockade? I have never thought of one type of brachial plexus block wearing off significantly quicker than another, all other things being equal.

And ironically, though maybe it's because I have done way more axillary blocks than supraclavicular blocks through training and in practice, but I feel like my axillary blocks last longer than my supraclaviculars.

 

[Sonny Crocket]

I find that if any hand surgery is going to be done with sedation only or totally awake, I will often block the whole arm with a supraclavicular block because of the tourniquet.
If the patient is going to get a GA, you can just block the medial, ulnar and radial nerves individually, depending on what you need. It is very easy to do these blocks.

 

[BLADEMDA]

I always encourage new attendings to track their blocks in pacu and postop. Those studies are not exactly what I see in the real world.

In my hands an ISB is superior than any other block for shoulder surgery. The others work well just not as well. By adding a superficial cervical plexus block the C3 and C4 dermatomes are covered which means that for open shoulders or clavicle repairs the post op pain relief is outstanding.

Duration of postop analgesia is a complicated issue. For some reason a SCB or ICB provides longer postop analgesia than an axillary block. I have tracked this for myself over hundreds of blocks. I have also tracked my local anesthetic (type and concentration as well as volume) for hundreds of blocks. I have tried many adjuvants To enhance duration of postop analgesia and tracked the outcomes.

For most of you I recommend that you do what you are good at and what you have tracked in terms of outcomes. There is no perfect formula but there are many which work quite well. Don’t be afraid to tinker with your own formula (within reason based on published literature) and track the outcomes.

 

[secretasianman]

How many mls of local are you guys putting in?

 

[BLADEMDA]

The amount of local used is typically 15-30 Mls with most using 30 Mls for SCB and ICB.
For my ISB I use 20 Mls and duration of postop analgesia is similar to 30 Mls. FYI, the concentration of Bupivacaine needed for good postop analgesia is 0.25-0.375 percent. So, even though many use 0.5.percent Bup that may be overkill if a GA with LMA is also administered. Again, duration of postop analgesia with 0.25-0.375 percent Bup is still quite good vs 0.5 percent Bup. But, don’t just take my word for it give it a try and see for yourself.

 

[deleted875186]

The amount of local used is typically 15-30 Mls with most using 30 Mls for SCB and ICB.
For my ISB I use 20 Mls and duration of postop analgesia is similar to 30 Mls. FYI, the concentration of Bupivacaine needed for good postop analgesia is 0.25-0.375 percent. So, even though many use 0.5.percent Bup that may be overkill if a GA with LMA is also administered. Again, duration of postop analgesia with 0.25-0.375 percent Bup is still quite good vs 0.5 percent Bup. But, don’t just take my word for it give it a try and see for yourself.

Do you know of any reference for duration of block versus bupi concentration or bupi total dose. In residency most people used 0.25 which seemed to offer the same duration as 0.375 or 0.5 but I never found any evidence that one is better than the other.

 

[BLADEMDA]

Do you know of any reference for duration of block versus bupi concentration or bupi total dose. In residency most people used 0.25 which seemed to offer the same duration as 0.375 or 0.5 but I never found any evidence that one is better than the other.

That’s my point. The literature is very scarce in this area. Most of it is out of date because the authors didn’t utilize u/s which results in shorter duration of postop analgesia. I can tell you from my experience that 0.25 percent Bup is very good but not quite as good as 0.5 percent Bup. The higher concentration using 30 ml results in a 1-2 more hours of postop analgesia. But, is it worth it to double the concentration of local just to pick up an extra 1-2 hours? That’s a professional decision.

As for volume, to achieve A high success rate when performing a SCB or ICB the data shows 25-35 Mls as recommended. I typical use 30 Mls with excellent success. Yes, you can get away with less volume but the failure rate goes up slightly.

With all the research going on in academic centers these questions should have already been answered. The answers in the literature are either pre ultrasound or simply incorrect.

Don’t take my word for it. I recommend you try it in your practice. Your results will likely mirror mine.