Epidural Ligament Engagement Feel

This forum made possible through the generous support of SDN members, donors, and sponsors. Thank you.
P

propadex

Full Member
10+ Year Member
Joined
May 24, 2011
Messages
57
Reaction score
18
At my institution we do epidurals w/ LOR to air in plastic syringes which are incredibly sensitive (impossible to inject air into skin/subQ/muscle). So I insert my touhy to 3 cm unless the patient is thin, attach my syringe, and start testing for LOR. Very easy and safe but slow. An attending encouraged me to try using a glass syringe with saline and I quickly realized it is not nearly as sensitive. It is very easy to inject into subQ or muscle and so I have to engage ligament before I can use it. My questions for attendings who use this method are:

1) Do you try to appreciate engagement of the interspinous ligament and then engagement of the ligamentum flavum? My understanding is that interspinous will give a "gritty" sensation as if pushing through a bag of tightly packed sand, followed by a subtle increase in resistance or crunch to indicate you are in ligamentum flavum
2) Do you attach your glass/saline syringe after you think you have engaged interspinous or after you think you have advanced into ligamentum?
3) Are there patients with soft/mushy ligaments that are difficult to feel? If so, is it possible to wet tap a patient by inserting a touhy by feel attempting to engage the ligament and getting no resistance but instead just being surprised by a wet tap? Or is it possible to engage interspinous and try to advance into ligament but don't feel anything and again be surprised by a wet tap?

Thanks in advance for your expertise!
Members don't see this ad.
 
I think it's a good idea to learn both. I had a hard time adjusting because I exclusively used plastic and the place I went to after residency only had glass.
 
propadex said:
At my institution we do epidurals w/ LOR to air in plastic syringes which are incredibly sensitive (impossible to inject air into skin/subQ/muscle). So I insert my touhy to 3 cm unless the patient is thin, attach my syringe, and start testing for LOR. Very easy and safe but slow. An attending encouraged me to try using a glass syringe with saline and I quickly realized it is not nearly as sensitive. It is very easy to inject into subQ or muscle and so I have to engage ligament before I can use it. My questions for attendings who use this method are:

1) Do you try to appreciate engagement of the interspinous ligament and then engagement of the ligamentum flavum? My understanding is that interspinous will give a "gritty" sensation as if pushing through a bag of tightly packed sand, followed by a subtle increase in resistance or crunch to indicate you are in ligamentum flavum
2) Do you attach your glass/saline syringe after you think you have engaged interspinous or after you think you have advanced into ligamentum?
3) Are there patients with soft/mushy ligaments that are difficult to feel? If so, is it possible to wet tap a patient by inserting a touhy by feel attempting to engage the ligament and getting no resistance but instead just being surprised by a wet tap? Or is it possible to engage interspinous and try to advance into ligament but don't feel anything and again be surprised by a wet tap?

Thanks in advance for your expertise!
Click to expand...

My first wet tap was the scenario you proposed in #3. Felt nothing until I did feel something and when I went to put the syringe on our came csf lol.

After that I started doing what you currently do which is inserting to around 3 cm and then attaching my LOR syringe. If it's very loose with saline then I will advance until the saline is very resistant which means I'm in one of the ligaments.

Usually my epidurals take a few minutes. Idk what the point is in going faster if im worried it's gonna cause higher rate of wet taps.
 
Members don't see this ad :)
I strongly believe that LOR with saline (and a tiny air bubble) while continuously advancing slowly with firm pressure after your initial Tuohy insertion is the safest, and fastest, way to do consistent epidurals.
You will still feel the engagement of the ligament, and will immediately push it away once through with your saline, also decreasing the likelihood of a wet tap. Not to mention reduction in patchy blocks by injecting 3-5 cc of air in the epidural space. It’s a wonderful and knowing feeling this way when you enter the space; Though I understand why academic attendings want you using air, so they can see if you get CSF of course.

Do a few with air if they demand, but make sure you are comfortable and facile with the LOR to saline when you graduate , as that is how it is most often done in the “real world.”
 
I will always try to hit spinous process with the finder needle (unless the SP is prominent enough to jut out and be visible through the skin).

At that point I expect engagement to occur 2-3 cm deeper than that point.

I typically do a plastic syringe with saline. I’ll put the syringe after I feel the needle engage into something and then advance the syringe/needle apparatus by pushing (while extending) with the extensor surface of my right index finger. Strong enough to advance the setup with a touch of extra help from my left hand, but when LOR strikes, it is only strong enough to push the saline into the space, not strong enough to further advance the needle.

For spinous processes that cannot be located by (deeper than) finder needle, I know loss is going to be at 5+ cm.

To answer your 3 questions:
1. I only appreciate some sense of engagement. I err on the side of placing syringe on the sooner side to avoid wet tap. Typically as I advance, there is stronger and stronger engagement (like inserting the needle through Brie cheese and then into a hard block of cheddar). I think there is too much patient variability to say “this is flavum” or “this is interspinous.”

2. Engagement of any ligament, so probably 80/20 interspinous/flavum.

3. Sure there are patients with mushy ligaments, anatomical changes/back surgery that can distort or obliterate flavum. By knowing how deep spinous process is, you should get a real sense of where you will expect loss.

Hope that helps.
 
I learned in residency with LOR to glass, I used to attach the syringe early, and would insert toughy up to 4 cm, and then beyond that use the LOR to saline. This can result in a false loss as you noted. By the end of residency I would slowly advance the toughy until I feel ligament, and then attach LOR syringe with saline, and use a continuous technique. This is undoubtedly the fastest and most consistent. In a very obese patient, this might mean advancing the toughy to 7cm or a pretty good depth which can be a bit unnerving. I think the more you practice feeling the tissues while advancing the needle the better you get at it.

I do the pain clinic, my experience in the clinic suggests that in general the bigger gauge the toughy, the easy it is to feel tissue and identify ligament. Coming in paramedian rather than exactly midline gets a bigger bite of ligament and helps with a good loss. Air is more sensitive than saline. Doing them blind will unfortunately result in some false losses and misplaced epidurals even in expert hands. Thoracic epidurals need to be done paramedian, hit lamina and walk off, then attach a LOR syringe, I am amazed I was ever able to place these blind based on how difficult they can be in the pain clinic with fluoro.
 
i do glass with air. i put it on when i think its deep enough or i feel like i hit ligament. im not as aggressive as some others. it also depends on size of teh patient. sometimes i see attendings jabbing left and right in and out to like 8cm and im am certain in some instances they are probably wet tapping. because there are certainly instances someone insert the syringe and csf comes out
 
I’m in the south where BMIs over 50/60/70 are common. So inserting the tuohy only 3cm is unlikely to be successful here. I insert until I fully engage ligament. Often times the needle is close to hubbed already. Then glass LOR with local.

I’m pretty aggressive, but still couldn’t tell you the last time I had a wet tap. Not afraid of it though. Just part of the game.
 
JoelJoel84 said:
.

Do a few with air if they demand, but make sure you are comfortable and facile with the LOR to saline when you graduate , as that is how it is most often done in the “real world.”
Click to expand...
Lol what, I’ve been doing both thoracic and lumbars with glass+air for almost a decade. Am I in the fake world?


Cause AFAIK, no one technique has been definitively shown in the literature to be superior to the other.
 
anbuitachi said:
i do glass with air. i put it on when i think its deep enough or i feel like i hit ligament. im not as aggressive as some others. it also depends on size of teh patient. sometimes i see attendings jabbing left and right in and out to like 8cm and im am certain in some instances they are probably wet tapping. because there are certainly instances someone insert the syringe and csf comes out
Click to expand...
Yes, in my opinion aggressively jabbing or advancing the needle quickly is dangerous and unnecessary, it doesn’t make the procedure go faster.

I deliberately advance the toughy with two hands very gingerly while feeling the tissues, up until I appreciate ligament, if ever in doubt you can attach the LOR syringe or come back and pick a new angle.
 
Follow up question, but does anyone's techniques change if its thoracic vs lumbar? I've been confident with a handful of thoracic epidurals with LOR to saline and they've been duds. Is there a higher risk of pneumocephalus with thoracic vs lumbar?
 
JoelJoel84 said:
I strongly believe that LOR with saline (and a tiny air bubble) while continuously advancing slowly with firm pressure after your initial Tuohy insertion is the safest, and fastest, way to do consistent epidurals.
You will still feel the engagement of the ligament, and will immediately push it away once through with your saline, also decreasing the likelihood of a wet tap. Not to mention reduction in patchy blocks by injecting 3-5 cc of air in the epidural space. It’s a wonderful and knowing feeling this way when you enter the space; Though I understand why academic attendings want you using air, so they can see if you get CSF of course.

Do a few with air if they demand, but make sure you are comfortable and facile with the LOR to saline when you graduate , as that is how it is most often done in the “real world.”
Click to expand...
Ive been doing ob for a while and I have never used saline. My colleagues who do use saline are getting more wet taps.
 
Members don't see this ad :)
Clinicall said:
Follow up question, but does anyone's techniques change if its thoracic vs lumbar? I've been confident with a handful of thoracic epidurals with LOR to saline and they've been duds. Is there a higher risk of pneumocephalus with thoracic vs lumbar?
Click to expand...
Yes, thoracic is LOR to saline with paramedian technique. You must hit lamina and walk off before attaching syringe.
 
I do thoracic with LOR to air in the middle no problems. Always works except one time when I placed it too deep but pulled it back and it was fine.
 
Incidence of wet taps has nothing to do with using saline vs air. When you wet tap with air its much worse as stated above. Studies show that if the proceduralist uses the method they are most comfortable and consistent with they have the best outcomes (ie air or saline depending on your preference).
 
Last edited:
DrOwnage said:
Incidence of wet taps has nothing to do with using saline vs air. When you wet tap with air its much worse as stated above. Studies show that if the proceduralist uses the method they are most comfortable and consistent with they have the best outcomes (ie air or saline depending on your preference).
Click to expand...

I never wet tap though
 
Apologies, this was not meant to generate a LOR to air vs. saline debate. Rather I was trying to understand the subtle tactile nuances of the procedure. I appreciate those that answered my questions. Thank you!
 
propadex said:
Apologies, this was not meant to generate a LOR to air vs. saline debate. Rather I was trying to understand the subtle tactile nuances of the procedure. I appreciate those that answered my questions. Thank you!
Click to expand...
Air is more sensative, no doubt about it, it’s discouraged in residents because it will turn a wet tap into a pneumocephalus.
 
i dont like the continuous pressure you have to exert with saline
 
To OP: I think the tactile sensation is similar to modeling clay or cheddar cheese. As others have said, it sometimes becomes more firm at the ligamentum flavum, sometimes even with a perceptible crunch as the needle penetrates it. I think there is a significant variation between patients and the part of the ligament engaged. For average patients, when the needle is engaged firmly in the interspinous ligament the plunger should be difficult to depress when full of saline.

I think it’s advantageous to learn a variety of techniques so you can apply them to differing situations when they arise. For instance, for me and for a lot of people, using a continuous technique with saline and a small bubble is the fastest and most convenient way to place a lumbar epidural, but I feel strongly that switching to an incremental technique with air when the tactile sensation is ambiguous has helped me avoid a few dural punctures and successfully place some more challenging ones.
 
dipriMAN said:
Yes, in my opinion aggressively jabbing or advancing the needle quickly is dangerous and unnecessary, it doesn’t make the procedure go faster.

I deliberately advance the toughy with two hands very gingerly while feeling the tissues, up until I appreciate ligament, if ever in doubt you can attach the LOR syringe or come back and pick a new angle.
Click to expand...
I'm not sure because I'm not there, but sometimes they may immediately reinsert deeply if they've already contacted os and were noting the depth.

To chime in, I use continuous technique midline approach w/ saline and glass for lumbar epidurals and paramedian intermittent technique with saline and glass for thoracics.
 
glass/plastic/air/saline...use whatever you are most comfortable with. The only change in technique/practice I have made over the years is that if LOR is a little iffy and catheter won't thread, then I pull back and start over instead of advancing a little more. Or even if the LOR is perfect and the catheter won't thread off. I just assume I am off just a smidge left or right.
 
Mman said:
glass/plastic/air/saline...use whatever you are most comfortable with. The only change in technique/practice I have made over the years is that if LOR is a little iffy and catheter won't thread, then I pull back and start over instead of advancing a little more. Or even if the LOR is perfect and the catheter won't thread off. I just assume I am off just a smidge left or right.
Click to expand...
Agreed

I put in a labor epidural a few days ago that felt a little iffy, but the catheter threaded. I was busy and had other stuff pending so I called it good.

A couple hours later I was back doing the epidural again. Should've done what I knew was right the first time and just pulled back and LOR'd again.
 
Mman said:
glass/plastic/air/saline...use whatever you are most comfortable with. The only change in technique/practice I have made over the years is that if LOR is a little iffy and catheter won't thread, then I pull back and start over instead of advancing a little more. Or even if the LOR is perfect and the catheter won't thread off. I just assume I am off just a smidge left or right.
Click to expand...
Good advice, very reasonable approach. One alternative to this I suggest is that if you get LOR, but can’t thread the catheter, try performing a CSE to verify placement (and appease the patient), and then thread a 20 gauge nylon catheter which will often thread better than the 19 gauge.
 
pgg said:
Agreed

I put in a labor epidural a few days ago that felt a little iffy, but the catheter threaded. I was busy and had other stuff pending so I called it good.

A couple hours later I was back doing the epidural again. Should've done what I knew was right the first time and just pulled back and LOR'd again.
Click to expand...
Agreed, this is the way to go with epidurals, if ever in doubt, pull it out. Don’t advance, just come out and do another approach.
 
propadex said:
At my institution we do epidurals w/ LOR to air in plastic syringes which are incredibly sensitive (impossible to inject air into skin/subQ/muscle). So I insert my touhy to 3 cm unless the patient is thin, attach my syringe, and start testing for LOR. Very easy and safe but slow. An attending encouraged me to try using a glass syringe with saline and I quickly realized it is not nearly as sensitive. It is very easy to inject into subQ or muscle and so I have to engage ligament before I can use it. My questions for attendings who use this method are:

1) Do you try to appreciate engagement of the interspinous ligament and then engagement of the ligamentum flavum? My understanding is that interspinous will give a "gritty" sensation as if pushing through a bag of tightly packed sand, followed by a subtle increase in resistance or crunch to indicate you are in ligamentum flavum
2) Do you attach your glass/saline syringe after you think you have engaged interspinous or after you think you have advanced into ligamentum?
3) Are there patients with soft/mushy ligaments that are difficult to feel? If so, is it possible to wet tap a patient by inserting a touhy by feel attempting to engage the ligament and getting no resistance but instead just being surprised by a wet tap? Or is it possible to engage interspinous and try to advance into ligament but don't feel anything and again be surprised by a wet tap?

Thanks in advance for your expertise!
Click to expand...

I’ll answer your questions:
1.) No, I do not try to differentiate between interspinous ligament and ligamentum flavum.
2.) I attached my syringe based on body habitus. I actually get more nervous with the real thin patients where LOR is at 2cm. Most of the time I attach the syringe around 3cm. I never got comfortable with the continuous pressure technique, so I use intermittent taps. The key is to use light taps. When I am attaching at 3cm and I know it’s a good bit deeper, I advance pretty quickly until I feel the resistance stiffen up a bit. At this point I usually know I’ve engaged the ligament and will slow my advance.
3.) Every patient’s ligament will feel different. Some have the satisfying gritty or crunchy feeling as you advance, but other will feel like that block of cheddar. My wet taps have come in a few flavors:
-Slips: this is when I think my needle is partially hitting bone and I push a little too hard and the needle advances further than I intended. If I feel like I am having to push a little too hard to advance then I back up and redirect a bit.
-Mushy ligament: this is when I get a loss, but the ligament never gave me great resistance to begin with, so it didn’t really feel like a loss. The next tiny advance goes through the dura. Now in these instances, I don’t advance. I’ll try to thread a catheter, but unless it goes easy, I will try again up or down a level
-Bucking broncos: these are the patients that can’t sit still. I’ve had a wet tap or two where the woman wiggles at the exact wrong moment.

Honestly, it’s just one of those things you have to do many times.
 
If you intubate with a Mac blade you should use air...saline if you use a Miller...
 
After answering this thread I’ve switched from air back to saline for all my epidurals for the last few weeks or si, and have to say the LOR with saline is much more satisfying. I still beleive air is more sensitive.
 
Last edited by a moderator:
GravelRider said:
I actually get more nervous with the real thin patients where LOR is at 2cm.
Click to expand...

I have never had LOR < 3 cm. And the few I have had a 3 CM were all around like 110 or 120 lbs at full term. Average length of the spinous process itself is about 3 cm or so, and yes when you can see them poking out at you it is possible to be starting at skin less than that length, although it is also farther to the epidural space than the just the length of the spinous process.
 
Mman said:
I have never had LOR < 3 cm. And the few I have had a 3 CM were all around like 110 or 120 lbs at full term. Average length of the spinous process itself is about 3 cm or so, and yes when you can see them poking out at you it is possible to be starting at skin less than that length, although it is also farther to the epidural space than the just the length of the spinous process.
Click to expand...
I have. 2.5 cm.
 
propadex said:
Apologies, this was not meant to generate a LOR to air vs. saline debate. Rather I was trying to understand the subtle tactile nuances of the procedure. I appreciate those that answered my questions. Thank you!
Click to expand...
Butter butter butter dart board.
 
GassYous said:
I do thoracic with LOR to air in the middle no problems. Always works except one time when I placed it too deep but pulled it back and it was fine.
Click to expand...
Deeper as in, Tuohy in the spinal cord or Tuohy in the lung?

I had a junior co-resident who performed a “through-and-through” wet tap and hit the back of the vertebral body. Patient had a PDPH for years after, ended up going on disability. Myelogram confirmed both dural punctures.
 
Mman said:
I am not doubting it is possible, just exceedingly rare.
Click to expand...
Twice during residency. Both just shy of 3cm (probably ~2.8). I remember when I was first learning to do epidurals as an intern people would tell me "the first 3 are free".

Now I just judge based on body habitus. Super skinny, I may start checking as early as 2-2.5cm. super obese, I'm driving that needle 5-7cm before I ever put on my LOR syringe.
 
Greenbayslacker said:
Deeper as in, Tuohy in the spinal cord or Tuohy in the lung?

I had a junior co-resident who performed a “through-and-through” wet tap and hit the back of the vertebral body. Patient had a PDPH for years after, ended up going on disability. Myelogram confirmed both dural punctures.
Click to expand...

Deeper as in the catheter was too deep
 
ethilo said:
I only use saline. Air has risk of introducing pneumocephalus and I've seen it a couple times where patients get a posterior neck pain and low and behold it was LOR to air. Saline is benign.
Click to expand...
I agree with you that saline is a nice technique but air is safe in the right hands. If the amount of air injected is less than 3 mls then there won't be an issue with 1 sided blocks or air in the brain. But, with multiple attempts using air the chances increase that some of that air will end up in the epidural space.

No technique is superior to the other but you must get familiar with the technique you are going to use and perfect it.
 
Mman said:
I am not doubting it is possible, just exceedingly rare.
Click to expand...
The chance of getting a wet tap is actually higher in very thin patients with low BMIs vs those with high BMIs. That's my experience as the distance to the epidural space is narrower and the gap between the epidural space and the dura is also smaller. In addition, the odds of getting a severe headache is much higher in the thinner patient.

So, the next time you get a BMI over 35 or 40 look on the bright side as you sweat your way into the epidural space.
 
BLADEMDA said:
The chance of getting a wet tap is actually higher in very thin patients with low BMIs vs those with high BMIs. That's my experience as the distance to the epidural space is narrower and the gap between the epidural space and the dura is also smaller. In addition, the odds of getting a severe headache is much higher in the thinner patient.

So, the next time you get a BMI over 35 or 40 look on the bright side as you sweat your way into the epidural space.
Click to expand...

I have said the same thing for years. BMI of 40 or 50 is generally easy and low worry for me
 
Mman said:
I have never had LOR < 3 cm. And the few I have had a 3 CM were all around like 110 or 120 lbs at full term. Average length of the spinous process itself is about 3 cm or so, and yes when you can see them poking out at you it is possible to be starting at skin less than that length, although it is also farther to the epidural space than the just the length of the spinous process.
Click to expand...

I’ve had it twice where LOR was <3cm…probably like 2.5 cm. My point is the thinner women make me more cautious because wet taps are more likely.
 
Greenbayslacker said:
Deeper as in, Tuohy in the spinal cord or Tuohy in the lung?

I had a junior co-resident who performed a “through-and-through” wet tap and hit the back of the vertebral body. Patient had a PDPH for years after, ended up going on disability. Myelogram confirmed both dural punctures.
Click to expand...
Did you do a through and through blood patch?
 
You must log in or register to reply here.

Similar threads

coffeebythelake
Ob epidural assessments
Replies
31
Views
2K
cchoukal
C
N
Dosing spinals for C/S after Epidural
2
Replies
76
Views
5K
deleted1183938
D
nimbus
Epidural for cosmetic surgery
Replies
3
Views
1K
bourg
B
D
Epidural Request with Cook/Foley Balloon still in place
Replies
17
Views
2K
DocVapor
DocVapor
GaseousClay
epidural possibly leading to autism paper
Replies
30
Views
3K
Mehd School
Mehd School
Top