Regional Block Question

[doctor712]

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Hey All,

I know I'll learn this in a few years, but perhaps I can get an answer now...?

I have been wondering why, when you do a spinal tap, a major concern doesn't seem to be PDPH, whereas when you perform an epidural, and it
becomes a wet tap, a spinal for all purposes, you see PDPH much more frequently...

So, I did some READING and discovered that the needle used for a spinal is much smaller in gauge than that which is used for an epidural. So, the opening created is less likely to leak and/or cause a yucky PDPH.

Having said that, since you are traversing the epidural space to perform a normal spinal (that is, a thin needle will have no problem getting across the epidural space because that's what's used for a spinal) WHY NOT always use a thin gauged needle even when performing an epidural? In order to prevent a PDPH IFyou get a wet tap.

Now, I know epidural wet taps hover at around 1%, so, a) why not use this method and b) do some of you tend to use this method when you are expecting difficult anatomy? c) what are the other downsides to using a spinal needle for an epidural?

thanks!
D712

 

[countingdays]

Hey All,

I know I'll learn this in a few years, but perhaps I can get an answer now...?

I have been wondering why, when you do a spinal tap, a major concern doesn't seem to be PDPH, whereas when you perform an epidural, and it
becomes a wet tap, a spinal for all purposes, you see PDPH much more frequently...

So, I did some READING and discovered that the needle used for a spinal is much smaller in gauge than that which is used for an epidural. So, the opening created is less likely to leak and/or cause a yucky PDPH.

Having said that, since you are traversing the epidural space to perform a normal spinal (that is, a thin needle will have no problem getting across the epidural space because that's what's used for a spinal) WHY NOT always use a thin gauged needle even when performing an epidural? In order to prevent a PDPH IFyou get a wet tap.

Now, I know epidural wet taps hover at around 1%, so, a) why not use this method and b) do some of you tend to use this method when you are expecting difficult anatomy? c) what are the other downsides to using a spinal needle for an epidural?

thanks!
D712

Just to clarify something for you, a spinal tap typically refers to a diagnostic lumbar puncture and is performed with a larger needle than a spinal/subarachnoid block and involves removing csf rather than injecting local anesthetic/narcotic/epi/clonidine/whatever.

You can't use that small a needle for an epidural because
a) you would not necessarily be able to tell you are in the epidural space
b) the epidural needle needs to be large enough that you can thread an epidural catheter through it.
(b doesn't apply to single shot epidurals of course)

 

[Planktonmd]

The reason why a large needle is used to do epidurals is because we use a technique called "loss of resistance" to detect passage into the epidural space, it is basically the ability to inject air or saline with minimal resistance.
This loss of resistance would be difficult to appreciate with a small needle.

As for PDPH after spinals you are partially right, in addition to the needle being smaller we usually use pencil point needles that do not have a sharp tip which minimize the incidence of headache by passing between the fibers rather than cutting them.

 

[doctor712]

Ahh, thanks you both! Yes, I've seen LOR and didn't know that wouldn't be appreciable with a smaller needle. The Pain guy I've observed took the time to really demonstrate the LOR for my eyes, bouncing the syringe, advance, advance, and suddenly, ALL the way in... really obvious. At least, I guess that's how it's supposed to be. 🙂

To clarify, LOR is used in translaminal but not caudal or transforaminal?
IF so, is this because the Ligementum Flavum (?) is only midline, and that's what you are passing through for LOR translaminal? OR, is LOR AFTER you are deep to LF and actually in space, thus able to inject into "space". I cannot seem to find a GREAT picture of all the layers you pass for epidural and spinal, on the web, and I lent my Miller out to a Prof so he can use it for his PChem class (gases and volatiles). I'd like to get this down because I've had a question or two about it during observing.

Another follow up would be, in the days before fluro, IF I am correct that LOR isn't used for transforaminal, how do/did you know you were in the space? I know replication of pain is always a big one, doctor asks, "Is that where the pain is, down your leg, back..." etc, so he knows he's getting the right spot, but, BEFORE you inject, without fluro, what's the method of knowing you are in?

(Gyp: Indeed, I meant a spinal block for anesthetic, not a spinal tap for diagnosis. Sorry about that!)

thanks again!
D712

 

[Bertelman]

Another follow up would be, in the days before fluro, IF I am correct that LOR isn't used for transforaminal, how do/did you know you were in the space? I know replication of pain is always a big one, doctor asks, "Is that where the pain is, down your leg, back..." etc, so he knows he's getting the right spot, but, BEFORE you inject, without fluro, what's the method of knowing you are in?

You are incorrect. LOR is used to confirm epidural space regardless of spinal segment (thoracic, caudal, lumbar) or approach (midline, transforaminal, paramedian).

 

[doctor712]

You are incorrect. LOR is used to confirm epidural space regardless of spinal segment (thoracic, caudal, lumbar) or approach (midline, transforaminal, paramedian).

Got it, thanks.

D712

 

[rsgillmd]

You are incorrect. LOR is used to confirm epidural space regardless of spinal segment (thoracic, caudal, lumbar) or approach (midline, transforaminal, paramedian).

Bert, you do your caudals with LOR? The ones I did on the kids I threaded an angiocath when I thought I was in the right space,, aspirated, and then injected. So its LOR in the sense that you make sure the injection goes smooth, but it's not LOR in the traditional sense of an epidural in the cervical, thoracic, or lumbar regions.

The caudals I did on adults in the pain room were under fluoro.

 

[pgg]

I have been wondering why, when you do a spinal tap, a major concern doesn't seem to be PDPH, whereas when you perform an epidural, and it becomes a wet tap, a spinal for all purposes, you see PDPH much more frequently...

In addition to what the others wrote - PDPH is a concern for diagnostic lumbar punctures (spinal taps). As a resident I did more blood patches for ER LPs than OB wet taps.

Typically our routine, deliberate dural punctures for spinal anesthesia are with 25 g pencil point needles, which carry a low risk of PDPH.

For LPs, the kits usually include 22g or even 20g cutting needles, which carry a substantial risk of PDPH. (And not to bash the ER guys, but they do fewer LPs than we do spinals, and they tend to do them in the more difficult lateral position - so their technique often involves multiple passes which also increases the risk of PDPH.)

 

[pgg]

I always did caudals (for kids) with a 19g B-bevel needle, no angiocath. Fluoro for adults.

 

[Bertelman]

Bert, you do your caudals with LOR? The ones I did on the kids I threaded an angiocath when I thought I was in the right space,, aspirated, and then injected. So its LOR in the sense that you make sure the injection goes smooth, but it's not LOR in the traditional sense of an epidural in the cervical, thoracic, or lumbar regions.

The caudals I did on adults in the pain room were under fluoro.

You're right.


***although I do recall seeing a LOR in the pain clinic for a caudal block on an adult

 

[doctor712]

Good stuff, thanks!
D712

 

[sevoflurane]

20 gauge angiocath. Left thumb feels for coccyx. Move cephalad until you feel the 2 sacral cornuae and sacral hiatus. Hold skin tightly with flexed thumb. Enter with right hand/angiocath directed at about 45° to skin at the point where your fingernail meets the skin/hiatus. Feel for a "click" as the sacro-coccygeal ligament is pierced. Aspirate. If you get csf or blood abort. If you get poop... = kick yourself in the arse.

 

[sevoflurane]

So my wife and I were studying peds for the orals last week. Ended up getting into caudal catheters for neonates. Apparently she has done a ton more than I have.

In discussing neonatal caudal catheters we could not figure out when epidural catheters were appropriate for the little ones. In other words, at what age do you go from neonatal caudal catheters to epidural catheters for POPM. Do you go on weight/height/age or is it just provider preference?

I've had LOR at 1cm before and it wasn't a neonate. Just curious.

 

[Jeff05]

So my wife and I were studying peds for the orals last week. Ended up getting into caudal catheters for neonates. Apparently she has done a ton more than I have.

In discussing neonatal caudal catheters we could not figure out when epidural catheters were appropriate for the little ones. In other words, at what age do you go from neonatal caudal catheters to epidural catheters for POPM. Do you go on weight/height/age or is it just provider preference?

I've had LOR at 1cm before and it wasn't a neonate. Just curious.

bertelman - LOR for transforaminal ESI? have not seen that.
also, when we do a spinal (no one really calls it spinal tap) we use 22-27 gauge needles. when we do epidurals we use 17 or 18G needles, not so we can get LOR, but so you can thread a catheter through it. i do my cervical epidurals with 20G or sometimes 22G epidural needles and can get LOR just fine.

 

[Bertelman]

bertelman - LOR for transforaminal ESI? have not seen that.

Pain clinic was kind of a foggy haze for me, so I can't swear I saw it, but I think so.

 

[IlDestriero]

Back when I did pain, I used to use the hanging drop technique for cervical ESIs.
I don't think that you could do a transforaminal ESI w/o fluoro, you wouldn't know how to guide the needle.
For caudals, I use an angiocath. For a caudal catheter, it depends on how far you need to go. It's much easier to place a thoracic epidural in a kid than thread the catheter all the way up.

 

[MRW]

I just rotated through a pain clinic and they did transforaminal epidurals under fluoro using spinal needles with no LOR. Placement was confirmed with contrast dye.

 

[lobelsteve]

As it relates to pain:

No epidural is performed without fluoro and contrast.

There is no lor for caudal or tfesi.