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Local Anaesthesia

Discussion in 'General Issues and Discussion Forum' started by bkelly11, Oct 10, 2013.

  1. bkelly11

    bkelly11 Active Member

    Members do not see these Ads. Sign Up.
    Are there any guidelines when using LA about the amount you should start with when trying to gain Anaesthesia of a digit??

    I use 2% Lignocaine and administer roughly about 0.5 mls dorsal and plantar on both medial and lateral aspects of the toe (1st), entering dorsally only.

    I know we all come in different shapes and sizes. So my question is apart from using as little as possible LA to gain Anaesthesia is there any suggested protocol/guidelines/research to state how we should do this apart from professional judgement?
  2. Deka08

    Deka08 Active Member

  3. bkelly11

    bkelly11 Active Member

    Hi Deka08

    I understand the MSD however, I'm looking to see if there is any documented evidence that we should start injecting a certain amount of LA and then progress from that amount.

    In Australia we use Lignocaine MSD 3mg/kg. So for a 100kg person MSD = 210 ml. I have never used anywhere near that amount. Clinical judgement is what I have used in the past and reflection on previous use/technique to use as little LA as possible.

    My question is. Is there a recommended dose Podiatrist's should inject to start with then check for Anaesthesia? I have searched with no success.

  4. drsarbes

    drsarbes Well-Known Member

    Xylocaine is very safe.
    It is not uncommon for various medical procedures to use upwards of 200-300 mg.
    In the foot, We commonly use 10 cc of 2% for a PT/ankle block and another 7 or 8 cc of .5% marcaine for postop pain control. I cannot recall, in thousands of injections, ever getting a toxic reactions.

    When injecting for a digital block you are at the very low end of the dosage. We commonly use 2cc of 2% for hallux blocks.

  5. bkelly11

    bkelly11 Active Member

    Hi Steve I get that it safe to use and fully understand MSD. I've been asked to produce a document. Most of what I have read states that you should use as little as possible, which i do, in my opinion.

    However, my manager has questioned how do we know what concentration to start with i.e. 0.5ml, 1ml, 1.5ml etc, etc. For me common sense prevails.

    My quetion is! Is there a concentration of LA recommended or guideliness to start with to gain anaesthesia, say for example in correspondance to body weight?

    I have searched the literature and found nothing.

    Thanks in advance for any help.

  6. LuckyLisfranc

    LuckyLisfranc Well-Known Member

    Huh? 210ml? I hope not!

    Assuming a plain 1% solution (10mg per ml), the MSD of lignocaine for a 100kg person is actually 300mg - which is equivalent to 30ml.

    I think, rather than be worried about minimum dose to create anaesthesia, you should worry more about accurately working out your MSD.

    Honestly, for all its worth, we use such tiny dosages for routine work that its a complete non-issue. A couple of ml here or there is not of concern as long as satisfactory anaesthesia is obtained. More important obviously if you are doing complex surgery requiring much larger volumes/dosages such as for popliteal/sciatic blocks.


  7. bkelly11

    bkelly11 Active Member

    2% LL. Thanks for the feedback all sorted.

  8. wdd

    wdd Well-Known Member

    Back in the 1970's (?) there was an article in the Journal of the American Podiatry Association called something like Minimal Dose Local Anaesthesia of the Foot. If you can locate it you might find it interesting reading.

    I would think that the 1ml<2ml of 1% or 2% of local anaesthetic that is used to anaesthetise each side of a digit represents the accumulated clinical judgement of all those who have attempted to render a toe insensitive.

    I am never sure what the MSD really tells you? Yes you want to avoid the build up in conductive tissues, especially the heart and the brain but the treatment for ventricular arrythmia can involve intravenous injection of up to 300mg of lignocaine in just 1hour.

    I get the impression that there is a big safety margin built into the MSDs and that 2mg<3mg per kg bodyweight up to 70kg injected largely into the interstitial spaces won't statistically take you anywhere near an adverse reaction.

    Given that in the foot and more especially in a toe you would have to be having a very bad day to inject all of the anaesthetic agent into a vein, especially if you aspirate and or use a moving needle technique the chances of significantly depressing the conductive tissue in the heart or brain must be approaching 0 as DrSArbes experience (#4) confirms.


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