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Why can't spinal anaesthesia work from chest down?

  1. Feb 8, 2014 #1
    Hello everyone

    Here are some questions I have about spinal anaesthesia

    1. I know it is usually done below L3 because that is where spinal cord ends and not done above that because spinal cord can get damaged. But can't a really skilled person give it above L3, because subarachnoid space ends before spinal cord? So if he stops at the right time wouldn't it work giving anaesthesia from a higher level.

    2. Why does the spinal anaesthetic agent only act below the point it was administered. Can't it diffuse up and affect the whole spinal cord?

    3. Why can you achieve higher level anaestheisa (Meaning from chest to toe) from epidural anaesthesia?

    4. What is the difference between paraesthesia and numbness. Don't they both mean lack of senastion?

    Thanks :smile:
  2. jcsd
  3. Feb 8, 2014 #2


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    If the entire spinal cord becomes anaesthetised, what do you think will happen to the patient's respiration?
  4. Feb 8, 2014 #3
    Thanks for the response :) Yeah respiratory centre would not work. But I mean not that high, why can't you give spinal from like T2 level, so only shoulder down will get paralysed. Isn't respiratory centre located in medulla oblongota, so why can't you give it a bit below that? What are the answers for my other questions.
  5. Feb 8, 2014 #4
    What about the diaphragm?
  6. Feb 8, 2014 #5


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    "C3, C4, C5 keep the diaphragm alive " :biggrin:

    You can do it at high levels, but like you mentioned there are increased complications the high up you go. High spinal or total spinal blocks are avoided because, like mentioned, you get respiratory effects. I suppose you could mechanically ventilate the patient but if going to this extreme then general anesthesia is safer and better anyway--so why not use that? Especially because with general, you don't run the risk of damaging the cord--a not so great complication of spinal blocks. So above the level of L1 it is not longer the preferred method.

    To answer your second question, yes it can diffuse upward. Though not much, but again this is a reason why high spinal blocks aren't preferred.

    I'm not sure by what you mean here "high level anasthesia". Do you have a source or can you explain better what you are asking here>?
  7. Feb 9, 2014 #6
    Thanks a lot for all the responses, especially Bobze :smile:

    The replies cleared most of my doubts.

    What I mean from the 3rd question is

    3) Since in epidural anesthesia, you only go to epidural space and there is less chance of damaging spinal cord, can't you give it above L1 (Not too high to block resp centre) to achieve anaesthesia in a greater region of the body. Why isn't this done regularly?

    4)Is epidural also given at spinal level (meaning below L1) in normal setup? If so what is the basic difference in action between them. I understand the difference in procedure (spinal is just one shot, epidural you can continuosuly administer drugs via catheter), what I'm asking is differenc e in action?

    5) If mothers in labour are given epidural, wouldn't the epidural catheter get dislodged when they are moving in pain? Sort of stupid question but just asking.

    Thanks :smile:
  8. Feb 9, 2014 #7


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    Why would this be needed?

    Women are given epidurals while in labor and it stops the pain. I don't know what you mean here either.
  9. Feb 9, 2014 #8


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    Yes, you can but for the same reasons mentioned before general anesthesia is preferred. Its really operator dependent, hospital policy, drug availability, anesthesiologist dependent etc. Epidurals take more training and skill to administer than spinal blocks.

    There isn't much difference. They can even use the same drugs. However, spinals typically tend to work faster and are easier to do, but would require repositioning the patient to readminister anesthetic during the procedure. Therefore, in longer procedures epidurals are preferred, because the catheter (soft) in place allows easy redosing. When both are placed correctly spinals also tend to cause more hypotension that requires intervention than epidurals. Epidurals can cause hypotension as well, but less so than spinals when done correctly.

    No. If the epidural is done correctly she shouldn't be moving in pain :). The catheters are soft, but are generally held in place with something like tegaderm.
  10. Feb 9, 2014 #9
    Thanks Bobze :smile:
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