Injecting spinal on NO CSF

[apma77]

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ok guys

this has now happened to me a cpl of times
I feel the dural pop....no csf...try a different level..same thing NO CSF
I inject....i get a good block!!

what is this about?? i see nothing in literature talkin about this phenomena

any ideas???

 

[urge]

ok guys

this has now happened to me a cpl of times
I feel the dural pop....no csf...try a different level..same thing NO CSF
I inject....i get a good block!!

what is this about?? i see nothing in literature talkin about this phenomena

any ideas???

Are you removing the stylette before sticking the pt?

 

[apma77]

ofcourse !!!

 

[pgg]

ofcourse !!!

Really? I think what urge was getting at is that if you stick a stylet-less needle into the patient, it may get clogged with the tissue you're going through and you won't get CSF back through it. The stylet should stay in until you feel your pop.

Before you inject, do you try aspirating? I can't think of any reason why a unclogged needle wouldn't allow aspiration of CSF if you were really in the subarachnoid space.

 

[Planktonmd]

ok guys

this has now happened to me a cpl of times
I feel the dural pop....no csf...try a different level..same thing NO CSF
I inject....i get a good block!!

what is this about?? i see nothing in literature talkin about this phenomena

any ideas???

Sometimes in the elderly dehydrated patients CSF volume is low and if you are doing the spinal in the lateral position with a small needle you might not get any CSF.
It's a tough call but there were times when I injected and got a great block without any initial CSF as well.
If you want to be sure use a # 22 needle in the sitting position.

 

[militarymd]

fat in the spinal space...

you see it sometimes on MRI.

low csf volume from dehydration???? that's pretty funny. I won't say anymore...I don't want to get banned.

 

[Planktonmd]

fat in the spinal space...

you see it sometimes on MRI.

low csf volume from dehydration???? that's pretty funny. I won't say anymore...I don't want to get banned.

Well, if you find it funny then it means you are beyond any attempt on my part to educate you so why should I even waste my time?

 

[militarymd]

Well, if you find it funny then it means you are beyond any attempt on my part to educate you so why should I even waste my time?

I want to say more, but your moderator status is just too intimidating for me.

so I'll let you be.

 

[Planktonmd]

I want to say more, but your moderator status is just too intimidating for me.

so I'll let you be.

I am glad that you find me intimidating, I think this started before I became a moderator though. 😍

 

[militarymd]

I am glad that you find me intimidating, I think this started before I became a moderator though. 😍

I guess elevation to moderator status has not elevated your level of insight.

Ever hear of the Monroe-Kelly doctrine as it applies to the central nervous system?

 

[Planktonmd]

I guess elevation to moderator status has not elevated your level of insight.

Ever hear of the Monroe-Kelly doctrine as it applies to the central nervous system?

So I understand that you are attempting to say something intelligent.
You are implying that a decrease in the plasma volume is not going to change CSF flow?
And you are trying to use data from traumatic brain edema to support your argument?

 

[militarymd]

So I understand that you are attempting to say something intelligent.
You are implying that a decrease in the plasma volume is not going to change CSF flow?
And you are trying to use data from traumatic brain edema to support your argument?

The single celled organism said that if you get dehydrated, your csf volume will go down, so that when you pass a spinal needle, you may not get csf back.

The x military doctor said...BS...and that a well known doctrine states that the volume in the CNS is constant and that if CSF volume decreases, something else increases.


Now we wait to see what the single celled organism has to say.

 

[SleepIsGood]

Or is APMA getting to something novel here?

Apma...all I can think is that perhaps you are giving an epidural injection and somehow enough of it is traversing the dura .

This is VERY unscientific. But I knew this one pain guy that said something like this. He told me that the reason he doesnt use Fluro is because he believes and has seen CLINICALLY relief substantially from his LESI. He has no way of knowing whether they're all in the Epidural space or if some is in the layers immediately above the epidural space. Regardless, it works. He feels that by the laws of mass action the medication will eventually spread to the substantia gelatinosa and work.

Yah, try telling this to an academic and he/she will have a MI.

 

[Planktonmd]

The single celled organism said that if you get dehydrated, your csf volume will go down, so that when you pass a spinal needle, you may not get csf back..

Correct, the single cell organism that intimidates the great fighter doctor is insisting that dehydration causes decrease of the flow of CSF through a small spinal needle.
And the intimidating single cell organism is further insisting that "FAT" can not explain why the elderly dehydrated patients almost always have decreased flow of CSF.
Actually the intimidating single cell organism is openly making fun of the great fighter mighty military doctor for coming up with such a silly explanation to a phenomenon we see every day.

The x military doctor said...BS...and that a well known doctrine states that the volume in the CNS is constant and that if CSF volume decreases, something else increases

The intimidating single cell organism will humbly insist that the great mighty unparalleled military doctor is a little bit confused on CNS physiology and quoting theories he doesn't fully understand and don't really apply to the situation being discussed.
😀

 

[urge]

Sometimes in the elderly dehydrated patients CSF volume is low and if you are doing the spinal in the lateral position with a small needle you might not get any CSF.

The lateral position sometimes takes forever to drip csf. But it will if you wait enough. I don't know about being dehydrated. I bet you got to have one foot in the grave before csf production drops to have a dry subarachnoid cavity.

Anyway, I'm in agreement with pgg.(That's nuts! Right?) I suspect the needle is clogged with skin/fat and that's why he cannot aspirate but when he injects it works.

Apma, do you aspirate after injecting?

 

[Planktonmd]

The lateral position sometimes takes forever to drip csf. But it will if you wait enough. I don't know about being dehydrated. I bet you got to have one foot in the grave before csf production drops to have a dry subarachnoid cavity.

Anyway, I'm in agreement with pgg.(That's nuts! Right?) I suspect the needle is clogged with skin/fat and that's why he cannot aspirate but when he injects it works.

Apma, do you aspirate after injecting?

Based on my personal experience: old dehydrated nursing home residents always have a decreased flow of CSF, and I find it difficult to accept that these patients have more epidural fat than younger healthier patients.

 

[apma77]

yes i always keep stylet in when poking the patient..and yes i did NOT get csf when i aspirated....but the quick spinal block that resulted bloggled my mind..one was in a 88 yr old patient , the other was a 27 yr old OB patient for c/s.

 

[Planktonmd]

yes i always keep stylet in when poking the patient..and yes i did NOT get csf when i aspirated....but the quick spinal block that resulted bloggled my mind..one was in a 88 yr old patient , the other was a 27 yr old OB patient for c/s.

What size needles are you using?

 

[militarymd]

OK ...oh great Plankton...

So when the CSF volume shrinks like you say....What takes up the space where the CSF used to be?

Monroe Kelly....says either you have more tissue or more blood....so what do you say?

Or does the bone surrounding all this shrink in size when the csf volume disappears.

 

[Planktonmd]

OK ...oh great Plankton...

So when the CSF volume shrinks like you say....What takes up the space where the CSF used to be?

Monroe Kelly....says either you have more tissue or more blood....so what do you say?

Or does the bone surrounding all this shrink in size when the csf volume disappears.

Is it possible that the decrease of CVP and resulting decrease of ICP could play a role in the CSF not flowing very well in dehydrated patients?
Would Monroe Kelly be upset if I suggested that this might be the problem here?
Do you think this might make more sense than "FAT" obstructing the needle?

 

[militarymd]

Sometimes in the elderly dehydrated patients CSF volume is low and if you are doing the spinal in the lateral position with a small needle you might not get any CSF.
It's a tough call but there were times when I injected and got a great block without any initial CSF as well.
If you want to be sure use a # 22 needle in the sitting position.

Is it possible that the decrease of CVP and resulting decrease of ICP could play a role in the CSF not flowing very well in dehydrated patients?
Would Monroe Kelly be upset if I suggested that this might be the problem here?
Do you think this might make more sense than "FAT" obstructing the needle?

You first said the "volume" is low.....now you say the "pressure" is low.....so which is it?

Your confusion frequently leads to confusion for others.

In case you didn't know....pressure and volume are 2 different things...although they relate to each other in a relationship that Monroe and Kelly talk about in the CNS.


so which is it...

 

[coprolalia]

Check me if I'm wrong, but if the volume is low enough that you aren't getting CSF through the needle then really bad things happen...

-copro

 

[urge]

Hey Mil, you are not talking about subarachnoid fat or are you?

 

[Planktonmd]

You first said the "volume" is low.....now you say the "pressure" is low.....so which is it?

Your confusion frequently leads to confusion for others.

In case you didn't know....pressure and volume are 2 different things...although they relate to each other in a relationship that Monroe and Kelly talk about in the CNS.


so which is it...

It's both, The low pressure causes low volume relatively because according to your "doctrine" that you memorized without understanding, the CNS tissue will shrink and the existing volume will occupy a bigger space, so there will be relative csf volume decrease, and the end result is less flow of CSF.
Have you been doing spinals on elderly debilitated people recently?

 

[militarymd]

Hey Mil, you are not talking about subarachnoid fat or are you?

yes ...from a discussion I had with a neurosurgeon.


and PLEEEase....someone tell the fool that he's a fool.

 

[Planktonmd]

yes ...from a discussion I had with a neurosurgeon.


and PLEEEase....someone tell the fool that he's a fool.

You are obviously unable to find something meaningful to say which doesn't surprise me a bit.
So a neurosurgeon "friend of your's" told you that "intrathecal fat" causes CSF to not flow very well in the elderly?

 

[militarymd]

yes ...from a discussion I had with a neurosurgeon.


and PLEEEase....someone tell the fool that he's a fool.

You are obviously unable to find something meaningful to say which doesn't surprise me a bit.
So a neurosurgeon "friend of your's" told you that "intrathecal fat" causes CSF to not flow very well in the elderly?

dude,

when did I say he was my friend????

you can't even quote people correctly.

 

[Planktonmd]

dude,

when did I say he was my friend????

you can't even quote people correctly.

So, he wasn't even your friend! 😱
You want us to believe the opinion of a Neurosurgeon that you don't even know very well???

 

[pd4emergence]

I have had 2 or 3 spinals that I got no CSF after removing the stylet but did with aspiration. One was the prototypical old lady for a hip. She was so thin that I knew I had to be in. I withdrew the sytlet and nada, aspirated and easily got CSF. The other was a fatty for c section. I had to do the spinal through an epidural needle. I knew it had to be in and it also aspirated easily. I don't see how you can trust a spinal if you don't see csf. Just my opinion.

 

[Arch Guillotti]

I have had a few of these as well. A couple of times nothing flowed but I was able to aspirate with a 1 cc tb type syringe. IIRC, these were on old shriveled up gomers. I have also done a few CSE's on laboring women when I didn't get spinal fluid either. Sometimes I would feel the dura pop and sometimes I wouldn't. In this case I always injected and didn't fool around w/aspirating. Most of the time the CSE dose worked. So I definitely have seen a spinal dose work despite seeing CSF. I have also had cases where I got good CSF flow and then injected but was unable to aspirate at the end, seems like these blocks always worked.

Now I ain't as smart as you fellas arguing back and forth, but this whole Monroe-Kelly doctrine business for SAB has me a little confused. In my mind this principle as it is stated only applies to the cranial vault because it is a fixed rigid structure.

 

[lobelsteve]

If you are in the IT space, and you can push fluid in, then you can get CSF out. If the needle tip is in the dura itself, you will have blocked flow out and when pushing fluid in, you push the dura away from the needle tip.

To say there is no fluid in there is assinine. The flow could be reduced, but the volume better remain near constant- or at least enough to keep the brain and cord completely bathed.

I agree with mil. Plankderator- you need a better explanation, especially when you are wrong and trying to convince us that somehow if the needle don't drip clear, there must be no fluid in the tank.

 

[Planktonmd]

If you are in the IT space, and you can push fluid in, then you can get CSF out. If the needle tip is in the dura itself, you will have blocked flow out and when pushing fluid in, you push the dura away from the needle tip.

To say there is no fluid in there is assinine. The flow could be reduced, but the volume better remain near constant- or at least enough to keep the brain and cord completely bathed.

I agree with mil. Plankderator- you need a better explanation, especially when you are wrong and trying to convince us that somehow if the needle don't drip clear, there must be no fluid in the tank.

How many spinal injections with a # 25 or # 27 needle have you done in your career?
How many Spinal anesthetics with any needle have you done?
How many debilitated nursing home patients have you performed a spinal anesthetic on ?
I hope the answer would be a few thousands of each because otherwise I will have difficulty convincing you of anything.

 

[jetproppilot]

How many spinal injections with a # 25 or # 27 needle have you done in your career?
How many Spinal anesthetics with any needle have you done?
How many debilitated nursing home patients have you performed a spinal anesthetic on ?
I hope the answer would be a few thousands of each because otherwise I will have difficulty convincing you of anything.

I've done, I dunno, a million?

Sorry.....exaggerating....half a million. (grin)

I don't bother with smaller gauge spinal needles in the elderly.....you're making your life complicated in an age group where PDPH isnt even an issue.

Drive the twenty two gauge to the subarachnoid space.

Since I only use a 22 in the older population, if I don't see fluid, I assume I'm not in the right place.

Feeling a pop is subjective...you can convince yourself you're there because you "felt" something, but as far as I'm concerned,

if there ain't fluid, I assume I ain't there.

Humbly disagree with the dehydration argument.

Injecting spinal medicine without seeing CSF is like inserting an endotracheal tube without seeing cords. You might get lucky, but usually not.

Mind as well play a slot machine.

No time for maybe in my book.

I'll try again until I'm sure.

 

[IN2B8R]

Proliferation of the pia and arachnoid is certainly a possibilty, so there's one explanation that might shed light onto why you get a dry tap, yet still accomplish a block. This proliferaion may or may not be symptomatic. This is a well known phenomenon--complication, really--of IT steroids injection and prior spine surgeries. You may get a better tap by changing the block level all together and moving onto a different interspace (usually superior). Adhesive arachnoiditis and cauda equina Sd can also give you similar problems, yet they generally are found in more symptomatic patients with paresis, urinary retention, etc, etc....

 

[Laurel123]

This has never happened to me because if I don't get CSF coming out through my spinal needle, then I assume I am not in the intrathecal space and I don't push my medication in. I believe I have done many spinals in my career and what I have found is that not every dural 'pop' feels the same. Sometimes it is text book. Sometimes it isn't. Sometimes you feel pops going through all sorts of different spaces and planes.

Some of the super old folks might have slow flowing CSF. But my C-section gals always have a nice brisk flow of CSF.

Oh, and the old guys get the 22gauge. CSF always flows through the 22 gauge if you are in the intrathecal space.

 

[Planktonmd]

I've done, I dunno, a million?

Sorry.....exaggerating....half a million. (grin)

I don't bother with smaller gauge spinal needles in the elderly.....you're making your life complicated in an age group where PDPH isnt even an issue.

Drive the twenty two gauge to the subarachnoid space.

Since I only use a 22 in the older population, if I don't see fluid, I assume I'm not in the right place.

Feeling a pop is subjective...you can convince yourself you're there because you "felt" something, but as far as I'm concerned,

if there ain't fluid, I assume I ain't there.

Humbly disagree with the dehydration argument.

Injecting spinal medicine without seeing CSF is like inserting an endotracheal tube without seeing cords. You might get lucky, but usually not.

Mind as well play a slot machine.

No time for maybe in my book.

I'll try again until I'm sure.

The discussion from the beginning was about small needles.
my initial statement was that:
If you are doing a spinal with a small needle in the lateral position on a dehydrated old person, there is a chance you will not get CSF flow.
Somehow it was turned into a discussion about the relationship between the different compartments within the skull!
Then a guy who is not even an anesthesiologist and who has never done one spinal has the nerves to tell us about his view although he has no idea what we are discussing.
We are not discussing the flow through a 22 needle, we are discussing the assumptions I mentioned: OLD, DEHYDRATED, LATERAL, and SMALL NEEDLE.
All the other arguments are valid, but excuse me: Intrathecal fat is not acceptable.
And regardless of what each of us thinks about any subject I think we can and should disagree respectfully and avoid turning these discussions into childish exchanges.

Anyway I think we covered all the aspects of the initial subject and I apologize for the exchange.

 

[jetproppilot]

The discussion from the beginning was about small needles.
my initial statement was that:
If you are doing a spinal with a small needle in the lateral position on a dehydrated old person, there is a chance you will not get CSF flow.
Somehow it was turned into a discussion about the relationship between the different compartments within the skull!
Then a guy who is not even an anesthesiologist and who has never done one spinal has the nerves to tell us about his view although he has no idea what we are discussing.
We are not discussing the flow through a 22 needle, we are discussing the assumptions I mentioned: OLD, DEHYDRATED, LATERAL, and SMALL NEEDLE.
All the other arguments are valid, but excuse me: Intrathecal fat is not acceptable.
And regardless of what each of us thinks about any subject I think we can and should disagree respectfully and avoid turning these discussions into childish exchanges.

hey, I like your use of bold face type!

I realize the conversation was about the use of small needles.

I offered my opinion that OLD and SMALLER NEEDLES is commonly a waste of time.

Knowing the frequent challenges of an old, osteophyte-ridden spine nearly devoid of disc space, in addition to the near-zero risk of post dural puncture headache in the elderly, why would a clinician choose to make the procedure harder by choosing a smaller gauge spinal needle?

I guarantee you'll take less second shots if you start with a 22.

With no additional sequelae when compared to a 25.

 

[Noyac]

Plank, with all due respect I think your off base here.

AS far as dry taps, I don't inject on dry taps. But if you look at the needle you see that the port is placed slightly back from the tip. I believe that as we get better and better with placing spinals (like when you have done 1/2 a million like Jet) we are very in tune to the different tissues we are traversing. We know when the pop is coming and instead of driving right through that pop like a resident learning, we stop immediately. Then the port is not all the way in. I advance just a hair and CSF flows usually. If you pop through the dura you may still be outside the arachnoid mater which as we all know the CSF is b/w the arachnoid and pia mater.

I have no proof of this but until someone gives me a better explanation, I will keep this one alive. And dehydration is not a better explanation in my book, sorry Plank.

 

[Noyac]

why would a clinician choose to make the procedure harder by choosing a smaller gauge spinal needle?

Umm because thats what's in the spinal kit and I'm too lazy to grab a 22g.

 

[Planktonmd]

Ok,
It seems that you guys want to continue this discussion so I am going to repeat my initial statement:

Sometimes in the elderly dehydrated patients CSF volume is low and if you are doing the spinal in the lateral position with a small needle you might not get any CSF.
It's a tough call but there were times when I injected and got a great block without any initial CSF as well.
If you want to be sure use a # 22 needle in the sitting position.

I never said that a 22 gauge needle wouldn't give you a better flow.
I just stated what I personally observed on few occasions and it happens to correlate with apma's experience.

 

[dhb]

happened to me once csf backflow but nothing on aspiration, good block

 

[militarymd]

Well, if you find it funny then it means you are beyond any attempt on my part to educate you so why should I even waste my time?

And regardless of what each of us thinks about any subject I think we can and should disagree respectfully and avoid turning these discussions into childish exchanges.

Anyway I think we covered all the aspects of the initial subject and I apologize for the exchange.

look who started it....

glass houses and rocks.....or is it stones????

 

[Planktonmd]

No, this is where it started.

low csf volume from dehydration???? that's pretty funny. I won't say anymore...I don't want to get banned.

And you are right I should have ignored you.

 

[Mman]

Now I ain't as smart as you fellas arguing back and forth, but this whole Monroe-Kelly doctrine business for SAB has me a little confused. In my mind this principle as it is stated only applies to the cranial vault because it is a fixed rigid structure.

That is my understanding as well. As far as I know, it is not valid when discussing the spinal column or CNS as a whole.

and for the sake of completeness, Monro-Kellie is the correct spelling

 

[lobelsteve]

The discussion from the beginning was about small needles.
my initial statement was that:
If you are doing a spinal with a small needle in the lateral position on a dehydrated old person, there is a chance you will not get CSF flow.
Somehow it was turned into a discussion about the relationship between the different compartments within the skull!
Then a guy who is not even an anesthesiologist and who has never done one spinal has the nerves to tell us about his view although he has no idea what we are discussing.
We are not discussing the flow through a 22 needle, we are discussing the assumptions I mentioned: OLD, DEHYDRATED, LATERAL, and SMALL NEEDLE.
All the other arguments are valid, but excuse me: Intrathecal fat is not acceptable.
And regardless of what each of us thinks about any subject I think we can and should disagree respectfully and avoid turning these discussions into childish exchanges.

Anyway I think we covered all the aspects of the initial subject and I apologize for the exchange.

Dare I assume only anesthesia folks have a knowledge of spinal anatomy? And I'm a "guy", but the MD puts me on the same ground as you. The role of Asst Program Director of an ACGME Pain Fellowship probably put me ahead of you when it comes to spinal anatomy. And your lack of understanding regarding SPINAL (extracranial) CSF volume as it relates to dehydration as well as your pointing out that I do not have experience in blindly putting a needle into the thecal sac has what to do with the price of tea in China?

Titre du document / Document title
Cerebrospinal fluid formation and absorption in dehydrated sheep
Auteur(s) / Author(s)
CHODOBSKI A. (1) ; SZMYDYNGER-CHODOBSKA J. (1) ; MCKINLEY M. J. (1) ;
Affiliation(s) du ou des auteurs / Author(s) Affiliation(s)
(1) Howard Florey Institute of Experimental Physiology and Medicine, University of Melbourne, Parkville, Victoria 3052, AUSTRALIE

Résumé / Abstract
Cerebrospinal fluid (CSF) plays an important role in the brain's adaptive response to acute osmotic disturbances. In the present experiments, the effect of 48-h dehydration on CSF formation and absorption rates was studied in conscious adult sheep. Animals had cannulas chronically implanted into the lateral cerebral ventricles and cisterna magna to enable the ventriculocisternal perfusion. A 48-h water deprivation altered neither CSF production nor resistance to CSF absorption. However, in the water-depleted sheep, intraventricular pressure tended to be lower than that found under control conditions. This likely resulted from decreased extracellular fluid volume and a subsequent drop in central venous pressure occurring in dehydrated animals. In conclusion, our findings provide evidence for the maintenance of CSF production during mild dehydration, which may play a role in the regulation of fluid balance in the brain during chronic hyperosmotic stress.
Revue / Journal Title
American journal of physiology. Renal physiology ISSN 1931-857X
Source / Source
1998, vol. 44, no2, pp. F235-F238 (22 ref.)

Granted their sheep, and I'm sure you have more experience putting things in sheep than I do, but still.

If you cannot get fluid to flow, you cannot be certain your needle tip is where you think it is.

http://www.cerebrospinalfluidresearch.com/content/5/1/11

I have never (outside of LP's during med school and Baclofen trials for Peds PM&R) thought about putting my MSO4 or Dilaudid test dose, or the Medtronic catheter into a space that I could not verify both with clear CSF flowing and with a myelogram on my fluoro. I also have no problem dumping in 50-70mg lidocaine w/o epi and MPF to allow a more comfortable tunneling of my catheter and pump placement. And I have an Anesthesiologist at the head of the bed for MAC.

Also, reading is Fun. SO is busting your balls knowing you take it so hard.

Dry tap and spinal anesthesia
Krishna Ramachandran, FRCA and Nandakumar Ponnusamy, DA
University Hospitals Coventry and Warwickshire, Coventry
To the Editor:

A major advantage of spinal anesthesia is its definitive endpoint i.e., the free flow of cerebrospinal fluid (CSF).1 Occasionally the needle is felt to be in the correct space, but on withdrawing the stylet there is no CSF flow (‘dry tap’). Common sense dictates that the procedure be repeated, but if the outcome remains the same and the patient refuses general anesthesia the options are limited. Consent was obtained from the hospital’s Research and Development Committee and the patient was informed of our intention to publish this case history.

A 60-yr-old obese (120 kg) male with a fear of general anesthesia, was admitted for removal of an infect-ed pin and plate from his tibia. Past history included a cervical laminectomy four years previously. He had been admitted for the same procedure (removal of pin and plate) a few months earlier. Spinal anesthesia was attempted, but abandoned after seven attempts, with no notation as to the nature of the difficulty experienced. As the patient refused a general anesthetic, surgery was postponed. On the current admission he remained adamant that he would only consent to regional anesthesia. A 24G Sprotte needle (Pajunk, Geisingen, Germany) was introduced into the L3–4 interspace in the sitting position and although a ‘give’ was felt, no CSF was seen. The procedure was repeated at the L2–3 interspace with the same result. Aspiration using a 2-mL syringe also failed to produce any CSF. At this point we injected 3 mL of heavy bupivacaine 0.5% in the L2–3 space and, within ten minutes he had a sensory block up to T12. Surgery proceeded uneventfully.

Causes of dry tap include a blocked needle, needle in the wrong space, spinal surgery and low CSF pressures. It is possible that in patients with ‘absent’ CSF or very low CSF pressure, the subarachnoid space is obliterated as the arachnoid "collapses" on the pia. This increases the volume of the subdural space and may explain the absence of CSF. In this setting an epidural may be considered, but is not without potential drawbacks as a dural tap may go unrecognized. A final block would not have subjected the patient to any undue risk because of the small volume of local anesthetic involved. While it is not our intention to advocate this practice in every patient who has a ‘dry tap’, we share this experience due to its infrequent clinical presentation.


Man this is fun.

 

[Noyac]

Granted their sheep, and I'm sure you have more experience putting things in sheep than I do, but still.

 

[Planktonmd]

.

Causes of dry tap include a blocked needle, needle in the wrong space, spinal surgery and low CSF pressures. It is possible that in patients with ‘absent’ CSF or very low CSF pressure, the subarachnoid space is obliterated as the arachnoid "collapses" on the pia. This increases the volume of the subdural space and may explain the absence of CSF. In this setting an epidural may be considered, but is not without potential drawbacks as a dural tap may go unrecognized. A final block would not have subjected the patient to any undue risk because of the small volume of local anesthetic involved. While it is not our intention to advocate this practice in every patient who has a ‘dry tap’, we share this experience due to its infrequent clinical presentation.....

Unfortunately I still have to tell you that you still have no idea what we are discussing and I strongly suggest that you read the things that you are copying from the internet before you post them.
The fact that you have never really given spinal anesthesia or any kind of anesthesia makes you less than qualified to discuss our field.
I am pretty sure that I had in the past explained to you that you lack basic knowledge and experience about anesthesiology but you seem to have forgotten.
It's OK I will remind you one more time.
And I will appreciate it if you keep the discussion at the level of professionalism you claim to have and keep the silly high school type humor to a minimum.

 

[Leverage]

Dare I assume only anesthesia folks have a knowledge of spinal anatomy? And I'm a "guy", but the MD puts me on the same ground as you. The role of Asst Program Director of an ACGME Pain Fellowship probably put me ahead of you when it comes to spinal anatomy. And your lack of understanding regarding SPINAL (extracranial) CSF volume as it relates to dehydration as well as your pointing out that I do not have experience in blindly putting a needle into the thecal sac has what to do with the price of tea in China?

Titre du document / Document title
Cerebrospinal fluid formation and absorption in dehydrated sheep
Auteur(s) / Author(s)
CHODOBSKI A. (1) ; SZMYDYNGER-CHODOBSKA J. (1) ; MCKINLEY M. J. (1) ;
Affiliation(s) du ou des auteurs / Author(s) Affiliation(s)
(1) Howard Florey Institute of Experimental Physiology and Medicine, University of Melbourne, Parkville, Victoria 3052, AUSTRALIE

Résumé / Abstract
Cerebrospinal fluid (CSF) plays an important role in the brain's adaptive response to acute osmotic disturbances. In the present experiments, the effect of 48-h dehydration on CSF formation and absorption rates was studied in conscious adult sheep. Animals had cannulas chronically implanted into the lateral cerebral ventricles and cisterna magna to enable the ventriculocisternal perfusion. A 48-h water deprivation altered neither CSF production nor resistance to CSF absorption. However, in the water-depleted sheep, intraventricular pressure tended to be lower than that found under control conditions. This likely resulted from decreased extracellular fluid volume and a subsequent drop in central venous pressure occurring in dehydrated animals. In conclusion, our findings provide evidence for the maintenance of CSF production during mild dehydration, which may play a role in the regulation of fluid balance in the brain during chronic hyperosmotic stress.
Revue / Journal Title
American journal of physiology. Renal physiology ISSN 1931-857X
Source / Source
1998, vol. 44, no2, pp. F235-F238 (22 ref.)

Granted their sheep, and I'm sure you have more experience putting things in sheep than I do, but still.

If you cannot get fluid to flow, you cannot be certain your needle tip is where you think it is.

http://www.cerebrospinalfluidresearch.com/content/5/1/11

I have never (outside of LP's during med school and Baclofen trials for Peds PM&R) thought about putting my MSO4 or Dilaudid test dose, or the Medtronic catheter into a space that I could not verify both with clear CSF flowing and with a myelogram on my fluoro. I also have no problem dumping in 50-70mg lidocaine w/o epi and MPF to allow a more comfortable tunneling of my catheter and pump placement. And I have an Anesthesiologist at the head of the bed for MAC.

Also, reading is Fun. SO is busting your balls knowing you take it so hard.

Dry tap and spinal anesthesia
Krishna Ramachandran, FRCA and Nandakumar Ponnusamy, DA
University Hospitals Coventry and Warwickshire, Coventry
To the Editor:

A major advantage of spinal anesthesia is its definitive endpoint i.e., the free flow of cerebrospinal fluid (CSF).1 Occasionally the needle is felt to be in the correct space, but on withdrawing the stylet there is no CSF flow (‘dry tap’). Common sense dictates that the procedure be repeated, but if the outcome remains the same and the patient refuses general anesthesia the options are limited. Consent was obtained from the hospital’s Research and Development Committee and the patient was informed of our intention to publish this case history.

A 60-yr-old obese (120 kg) male with a fear of general anesthesia, was admitted for removal of an infect-ed pin and plate from his tibia. Past history included a cervical laminectomy four years previously. He had been admitted for the same procedure (removal of pin and plate) a few months earlier. Spinal anesthesia was attempted, but abandoned after seven attempts, with no notation as to the nature of the difficulty experienced. As the patient refused a general anesthetic, surgery was postponed. On the current admission he remained adamant that he would only consent to regional anesthesia. A 24G Sprotte needle (Pajunk, Geisingen, Germany) was introduced into the L3–4 interspace in the sitting position and although a ‘give’ was felt, no CSF was seen. The procedure was repeated at the L2–3 interspace with the same result. Aspiration using a 2-mL syringe also failed to produce any CSF. At this point we injected 3 mL of heavy bupivacaine 0.5% in the L2–3 space and, within ten minutes he had a sensory block up to T12. Surgery proceeded uneventfully.

Causes of dry tap include a blocked needle, needle in the wrong space, spinal surgery and low CSF pressures. It is possible that in patients with ‘absent’ CSF or very low CSF pressure, the subarachnoid space is obliterated as the arachnoid "collapses" on the pia. This increases the volume of the subdural space and may explain the absence of CSF. In this setting an epidural may be considered, but is not without potential drawbacks as a dural tap may go unrecognized. A final block would not have subjected the patient to any undue risk because of the small volume of local anesthetic involved. While it is not our intention to advocate this practice in every patient who has a ‘dry tap’, we share this experience due to its infrequent clinical presentation.


Man this is fun.

I am just an idiot intern right now but posting support for your argument via the first "study" google could come up ( and be it sheep ), is not very strong. I got fifty bucks you have never read or heard about this lame study prior to you google search this evening??? LOL...

And I don't know why everyone is nit picking about volume and pressure anyhow. Sounds like everyone agrees you should use a bigger needle and have gravity help you out with the patient sitting up if possible. Also probably not a good idea to push your block with a dry tap though it has been done successfully.

 

[lobelsteve]

I am just an idiot intern right now but posting support for your argument via the first "study" google could come up ( and be it sheep ), is not very strong. I got fifty bucks you have never read or heard about this lame study prior to you google search this evening??? LOL...
.

Not a bet i'd take. Did you say lamb study, or lame study?
Postulate, refute. Show me the correlative study. I google both ways.
All the good studies are intracranial (because that's where clinical things occur and you "guys" need to help save lives). THere are studies on dehydration causing increased plasma and CSF vasopressin, causing increased volume in the CSF.

Background: in my field (Pain Medicine / Interventional Spine) doing things without fluoro is stongly discouraged. There are Anesthesia pain guys doing this for twenty + years and always report they never miss the epidural space and never get a wet tap. They also never know if they are there when doing pain procedures because we do not infuse bup/fent. We give 2-3cc NSS and 1-2cc steroids after a 1-2cc lido test dose. I know where I am in the spine because of contrast enhanced AP/lat fluoroscopy. I know ths does not translate well to spinal anesthesia because of the impossibility/insanity of fluoro for labor and delivery, or the OR. But this is a brief synopsis of where I am coming from.

http://forums.studentdoctor.net/showpost.php?p=6884054&postcount=30

Anytime somebody starts talking, "I've done this X numbr of times...." if the next thing is not "and this is the complication", or " and I still have no idea" - then it is highly likely the rest of the sentence is a lie.

 

[militarymd]

If anyone is interested...just look up the MRI studies look at CSF volume changes....invariably you will find that the "total volume" ...space within the confines of the bony covering (spinal column) remains constant.

If CSF decreases, blood volume increases....intraosseous contents remain very constant.