Anterior Sciatic Block

[Metalblade]

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Can someone walk me through how to do an anterior sciatic block without ultrasound? It seems like it would be a convenient block as you wouldn't have to flip someone over.

 

[Jay K]

http://www.nysora.com/peripheral_ne...58-Sciatic-Nerve-Block-Anterior-Approach.html

If you don't know nysora by now...

 

[SleepIsGood]

Can someone walk me through how to do an anterior sciatic block without ultrasound? It seems like it would be a convenient block as you wouldn't have to flip someone over.

Wouldnt recommend it w/o ultrasound. Obviously it can be done. Butw/o ultrasound and the inability to get it on the first shot, it can be quite painful. Youare going through a lot of muscle (in some maybe a lot of fat, but that's a diff issue). So when you go through a lot of muscle and you hve to 'redirect' often, it can be horrible.

With ultrasound, and if you know what you need to look for (ie you wont typically see the nerve with ultz doing an anterior approach), it can be a painless and satisfying block.

 

[aredoubleyou]

Its impossible to describe really, but relies purely on pattern recognition without (at least in my experience) any visualization of the actual nerve. Ive only done it for catheters, so you take a long toughy aim between the femur and artery, and hope you got the right spot (based on fascial layers and paterns on the u/s). Not an easy block.

 

[sevoflurane]

This is one of the few blocks I never use USD. Using it will slow me down. Well, if I'm doing a femoral, I'll look and see where my vessels are, but then I drop it. Feel for the femur, use a 22G stim needle and good sedation, hit femur, walk off the femur (you need to come back to the skin and readjust your angle or you'll bend your needle) and get the appropriate response. I've done them with USD, and besides needing a totally different and expensive mega probe, I find you end up wasting more time, especially with the biggens. I do these exclusively for knees. I can't remember the last time I did a labatt approach.

I've never placed a sciatic catheter via the anterior approach.

My 2 cents.

 

[sevoflurane]

You want to place your needle 90 degrees to the skin. After hitting the femur and coming back to the skin, you may need to push the skin over a bit to maintain something close to 90 degrees.
If you readjust your angle... remember that small changes proximally equal big changes at the tip of your needle. So small adjustments once you know where your femur is. Visualize it in your head... and remember the sciatic is a big ***** nerve which lives right behind the femur. Sometimes externally rotating the leg is useful.

Keep at it. It's a great block. 🙂

 

[SleepIsGood]

This is one of the few blocks I never use USD. Using it will slow me down. Well, if I'm doing a femoral, I'll look and see where my vessels are, but then I drop it. Feel for the femur, use a 22G stim needle and good sedation, hit femur, walk off the femur (you need to come back to the skin and readjust your angle or you'll bend your needle) and get the appropriate response. I've done them with USD, and besides needing a totally different and expensive mega probe, I find you end up wasting more time, especially with the biggens. I do these exclusively for knees. I can't remember the last time I did a labatt approach.

I've never placed a sciatic catheter via the anterior approach.

My 2 cents.

When I've done them, I've only placed anterior sciatci caths. Maybe that's why I'm biased. Why do you have to change probes? Yes, you should use the low frequency probe for doing a fem block, but in my opinion you can see everything you need to even with a high freq (the fem block is pretty easy anyways). Then using that same high freq probe and assuming you had Prepped and Draped the insertion site for the Ant Sciatic Nerve already, it's a clean shot.

See, it's difficult doing the 90 degrees to the skin approach when you are threading a cath using the anterior sciatic approach.

 

[Metalblade]

Sevo, where is the point of needle entry, ie how far distal on the thigh do you enter? And do you walk medially off the femur?

I tried looking with US. Cant really make out the nerve. What the best place for probe placement? And are you using a high or low freq probe? I find that I cant see the needle with a low freq probe so I tend to avoid it.

 

[lobelsteve]

You want to place your needle 90 degrees to the skin. After hitting the femur and coming back to the skin, you may need to push the skin over a bit to maintain something close to 90 degrees.
If you readjust your angle... remember that small changes proximally equal big changes at the tip of your needle. So small adjustments once you know where your femur is. Visualize it in your head... and remember the sciatic is a big ***** nerve which lives right behind the femur. Sometimes externally rotating the leg is useful.

Keep at it. It's a great block. 🙂

This is the worst picture I have ever seen. The piriformis comes off from the internal aspect of the sacrum at S2-4 and the sciatic notch is not the PSIS. Look at netter and not this drawing.

 

[sevoflurane]

This is the worst picture I have ever seen. The piriformis comes off from the internal aspect of the sacrum at S2-4 and the sciatic notch is not the PSIS. Look at netter and not this drawing.

That is not the point of the picture. Neither the piriformis or the internal aspect of the sacrum o rthe PSIS has anything to do with the ant. approach to the sciatic. Look at the right of the picture. Just shows you the relationship between the femur and the sciatic. That's all.

 

[sevoflurane]

Depends how fat your patients is. Biggens = bigger probe.

I've never done a ant. sciatic catheter, but here are my reservations:

A tuohy needles is a lot bigger than a 22g needle which means if you hit red you may have to hold pressure.
22g hurts, but good sedation makes things much better. I can't imagine what a tuohy needle feels like. How long of a tuohy needle would you use for a regular person? How about someone who has a large caliber thigh? Gotta bring out the harpoon right? Then thread a catheter. Ouch.

Sleepisgood has more experience at placing these catheters than I do. If it can be done safely, efficiently, with good delineation of anatomy and without the patient jumping off the bed, then it's something I would like to look into. If it's being taught then there is something to be said for this technique.

At this point, I prefer subgluteal approach for sciatic catheters.

 

[sevoflurane]

Sevo, where is the point of needle entry, ie how far distal on the thigh do you enter? And do you walk medially off the femur?

I tried looking with US. Cant really make out the nerve. What the best place for probe placement? And are you using a high or low freq probe? I find that I cant see the needle with a low freq probe so I tend to avoid it.

About one hands breath down from your inguinal ligament, right over the medial aspect of the femur after palpation. You walk off medially. If you look at the picture, you can see the proximal sciatic nerve is not entirely covered by the femur. That is where you want to hit it, this is the sweet spot. If you are looking straight down through the skin you would see the sciatic butting up right next to the medial aspect of the femur. Move further distally and the femur will hide your sciatic n. and you will have to angle a bit to hit it.

I also have a hard time seeing the sciatic nerve with the USD probe. It takes time or maybe I'm not good at it. Most my patients have BMI's >35. It's not like the brachial plexus where you look at subclavian artery and right next to it is your target.

This approach works great for me. It's truly a quick block. 😉

 

[sevoflurane]

Can someone walk me through how to do an anterior sciatic block without ultrasound? It seems like it would be a convenient block as you wouldn't have to flip someone over.

This is not exactly my technique... but pretty close. You really don't have to draw anything. Just feel for femur and go.

[YOUTUBE]http://www.youtube.com/watch?v=holyO_6uVMg[/YOUTUBE]

 

[pgg]

Thanks sevo - I'm going to try out the anterior approach for my next few knees. This looks like a technique well worth learning and doing.

 

[Idiopathic]

ultrasound is a wasted effort with this block, in case you havent realized that

 

[Idiopathic]

sevo are you doing these with femorals for tka?

 

[doctor712]

Quick question: In what scenario would this block, as opposed to an epidural, be used? For example? And why? Wouldn't an epidural at say (L-1 to L-5) block everything you need for a knee?

I understand you ALWAYS want options, and maybe you only want a true unilateral block only from X down to Y, or maybe there's some contraindication to an epidural in a certain patient (recent back surgery, unique access/anatomy)...

THANKS!

Curiously,
D712

 

[2ndyear]

All total joints get anticoagulated at some point, hence no epidural. Or if you do one for the case it gets pulled quickly.

 

[SleepIsGood]

Depends how fat your patients is. Biggens = bigger probe.

I've never done a ant. sciatic catheter, but here are my reservations:

A tuohy needles is a lot bigger than a 22g needle which means if you hit red you may have to hold pressure.
22g hurts, but good sedation makes things much better. I can't imagine what a tuohy needle feels like. How long of a tuohy needle would you use for a regular person? How about someone who has a large caliber thigh? Gotta bring out the harpoon right? Then thread a catheter. Ouch.

Sleepisgood has more experience at placing these catheters than I do. If it can be done safely, efficiently, with good delineation of anatomy and without the patient jumping off the bed, then it's something I would like to look into. If it's being taught then there is something to be said for this technique.

At this point, I prefer subgluteal approach for sciatic catheters.

Hey dude.

Yes, so what I've used in the past were these Braun white 20 G touhy needles. They arent metal. They are pretty much made from that same plastic material that the normal stimuplex needles are made from, but a little stiffer and therefore less malleable.

so as a result, the times I've done it, they werent painful as people have claimed it to be, especially since with ultrasound it was just a 1 pass thing.

I guess you can do with w/ or w/o ultz. The times I've done it, like I said, it's just a single prep of the leg. I can typically do both blocks using the same probe and keep things sterile, so why not?

I'd imagine at a place like sevo' where he has got great nurses to assist, this wouldnt take much more time to do.

 

[sevoflurane]

Hey dude.
I guess you can do with w/ or w/o ultz. The times I've done it, like I said, it's just a single prep of the leg. I can typically do both blocks using the same probe and keep things sterile, so why not?

Nice. 👍

 

[sevoflurane]

sevo are you doing these with femorals for tka?

Yep.

 

[Idiopathic]

Our standard here is intraop spinal/CSE with postop femoral nerve catheter out on POD 1. Ill admit that if they have any pain, its always back of the knee where a sciatic would benefit, but no way are we doing anterio sciatics routinely at our teaching institution with 10 attendings on pain service and new junior residents every 30 days. I probably did 3 during residency.

 

[sevoflurane]

...but no way are we doing anterio sciatics routinely at our teaching institution with 10 attendings on pain service and new junior residents every 30 days.

Why not? It's cosidered an "advanced technique", so your seniors can do it. The juniors can see it/drive the stimulator and then do it by the end of their rotation. By the time they are seniors again, the will be masters at it and will solidify their skills.

It worked well for us and our educational experience. I must have had 80+ by the end of residency. I bet your residents would enjoy learning this block.

Then again, your current setup is great for pain associated with TKA.

Just a thought. 🙂

 

[Idiopathic]

80 anterior sciatic is amazing as our residents do a lot of blocks, in my opinion, but we barely get 80 interscalene blocks. maybe if we didnt have our current paradigm it would be easier to get it going. we really dont do very many proximal sciatic blocks honestly, only for catheters for amputations, for the most part, and those are usually posterior approach. I agree its a smooth block in experienced hands, but it tends to just bog our service down when we do them.

 

[Idiopathic]

did you train at virginia mason, btw?

 

[sevoflurane]

Nope. Just lucky in that I came from an ortho heavy residency. Our attendings wrote books, chapters and papers in RA literature and were extremely motivated about teaching it. We were also lucky in that our class didn’t have a regional fellow when we were CA-3’s.
That service was exhausting compared to the OR's. Just friggn' busy all day long.

 

[Idiopathic]

ours is busy too, but with peripheral nerve catheters and all the labor that comes with those...the single shot service tends to suffer a little

 

[Metalblade]

I'm having a hard time seeing the needle under the low frequency probe, even if its a touhy. Is this common and just takes practice? Or am I doing something wrong?

 

[Idiopathic]

are you talking about the anterior sciatic approach? im of the opinion that its not an ultrasound block, but you should still be able to see the needle if you choose to do that so id wager that you might consider a different probe or that it could be a technique issue.

practice never hurt