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Local anaesthetic not working

Discussion in 'General Issues and Discussion Forum' started by Dennis Rehbock, Jul 10, 2013.

  1. Members do not see these Ads. Sign Up.
    Greetings Colleagues
    I have an unpleasant case of administering a LA and have it not work. It was a standard big toe block for a NWR and only half of the toe was numb. This was the side of the toe without the ingrown nail.
    I used some more LA to top it up but still no result.

    I tried to redo it again 2 days later and still no joy.

    The LA is Scandonest 3% plain (Mepivacaine hydrochloride 3%)

    How is this possible ? What now ?

    I may take the patient for a GA

  2. drsarbes

    drsarbes Well-Known Member

    Hi Dennis:
    In the literally thousands of blocks I have given I have had 2 patients that I could not get numb. In both cases I ended up just raising a wheel of lidocaine on the forearm just to test them, and neither one had numbness over the wheel.

    In effect, the lidocaine just did not work on these two patients.

    My take is...this stuff happens.

  3. W J Liggins

    W J Liggins Well-Known Member

    Hi Dennis

    Sounds as if you have a 'difficult one'. Although mepivacaine is my first choice, try 4% prilocaine, or failing that 2% lignocaine. All are chemically very close, but you never know.... My other thought is that there may be a variation in the anatomy. Try going very superficial, sufficiently so to blanche the skin. If that fails first time then go slightly deeper. If still ineffective try a full ring block.

    Please let us know if any of these suggestions are effective.

    Hope this helps.


  4. I have never seen a local anesthetic not work at all, except in infections. You may consider using more volume of local anesthetic in the digit than what you did. How much anesthetic did you actually use and did you consider that you just missed the nerve since the other parts of the toe was numb? Check each quadrant of the digit for sharp/dull sensation to determine which nerve you are missing so that you can direct any extra anesthetic into the area of nerve where the block did not take.

    If my first injection does not work well enough, which is less than 5%, I then give a block with double to triple the amount of anesthetic after the first injection. I then take the time to manually massage the local anesthetic into the tissues to make certain the anesthetic is reaching all the tissues in the area, in case of atypical nerve anatomy.

    Hope this helps.
  5. wdd

    wdd Well-Known Member

    Dear Dennis,

    In this case you know that the anaesthetic works and that the patient can be anaethetised as it effectively anaesthetised part of the toe.

    Is it possible that, on that side of the toe that was not numbed, pain sensation could have been knocked out, ie the patient could still feel all of the other components of sensation but not pain (the first sensation to be affected by local anaesthetic)?

    How do you envisage the nerve distribution to the toe, eg distinct dorsal and plantar branches or as a far more divided network? My success rate increased dramatically when I started to envisage the medial and lateral digital nerves as a plexus rather than as distinct branches and deposited the LA solution relatively evenly as I withdrew the needle. If I wanted to give a passing nod to the idea of distinct dorsal and plantar branches I would lean a bit more heaviliy on the plunger as I passed their imagined locations but always ensured that there was an unbroken line of anesthetic from as far plantar to as far dorsal as possible?

    Good luck,

  6. Rob Kidd

    Rob Kidd Well-Known Member

    Just a thought: in pronatory feet, with too-much medial lift off, soft tissue can get translated around the hallux. I have once known this to be the case where the digital NVBundles were largely lying dorso-plantar, not latero-medial. I am not advocating a "ring block" per se, but put some though into it. Rob
  7. wdd

    wdd Well-Known Member

    Sorry Dennis,

    This bit is not clear.

    It should read 'the dorsal and plantar branches of the medial and lateral digital nerves'. That is that rather than there being distinct dorsal and plantar nerves on each side of the toe there is a network of nerves on either side of the toe.

    I hope that makes sense.

  8. Bill:

    When you say "there is a network of nerves on either side of the toe", do you have any references for this anatomical anomaly? I acknowledge there are some anatomical variants to the neural anatomy of the hallux.


    However, hallux neural anatomy is usually quite basic with four nerves normally supplying sensory function to the hallux located at the dorsal-medial, dorsal-lateral, plantar-medial and plantar-lateral quadrants of the hallux (Kelikian AS (ed): Sarrafian's Anatomy of the Foot and Ankle: Descriptive, Topographic Functional. 3rd ed. Lippincott Willaims & Wilkins, Philadephias, 2011, pp. 381-427.). I have never seen a description of the neural anatomy of the hallux being described as a "network".

    Please explain.
  9. efuller

    efuller MVP

    It reminds me of the patient who so afraid of needles that he asked for the avulsion without anesthetic. I did it and he didn't flinch. Ex military. ?

    I'd consider no anesthesia before general. It depends a lot on the pain threshold of the patient.

    Just because there are no references that describe unusual anatomy doesn't mean that there is not unusual anatomy. I like the ring block suggestion, especially since you got the other side of the toe numb.

  10. wdd

    wdd Well-Known Member

    Hi Kevin,

    I'm afraid I can't give a nice clean reference like the one you've supplied and the one I will give, in a round the houses, vague sort of way, is considerably older than yours. However, if I make a stab at it, possibly someone out there will be able to home in on it more accurately?

    Back in the late 60's or early 70's probably while he was at Manchester, Louis Smidt (later Principal of London Foot Hospital) carried out a series of dissections to clarify the nerve distribution of the great toe. The series was small, I think it was about six but his findings were consistent and seemed to suggest that the arrangement he identified was not an anomaly. His essential finding was that the dorsal and plantar nerves were not distinct but had branched and subdivided to form networks.

    He wrote up his research and published it in 'The Chiropodist' sometime in the late 60's or early 70's. At the time there was probably nowhere else to publish it.

    Prior to reading this article I would, as I had been taught, insert the needle and progress it to the plantar aspect of the toe, without exiting on the plantar aspect (although I have seen it done and the student doing the injection, not realising that they had gone through the skin on the plantar aspect, 'injecting' local anaesthetic solution and drenching the tops of their own shoes much to their suprise). Having, in my head, an image of distinct doral and plantar nerves I would inject a bolus of anaesthetic to catch the plantar nerve, retract the needle and just before exiting inject a second bolus to catch the dorsal nerve.

    After reading Louis Smidt's article I modified my technique and while I would still put more more pressure on the plunger at the plantar and dorsal sites I would maintain some pressure on the plunger as I was pulling back from the plantar site and would maintain some pressure until the needle exited the toe.

    It seemed to cut down on the number of failed injections, the need to rub the toe to distribute the LA solution throughout the tissues or to give top-up injections and I thought that even if Louis' findings weren't representative of the general population it would give a greater chance of success. It felt like a win-win situation.

  11. BEN-HUR

    BEN-HUR Well-Known Member

    This is an interesting topic. I once had an individual not respond to local anaesthetic (2% Lignocaine). Admittedly the toe was mildly infected but I still have had luck anaesthetising such toes (some heavily infected). Despite my usual bilateral dorsal approach (of proximal phalange of Hallux), I also went from a plantar direction... all the while keeping this young individual’s MSD (maximum safe dose) in mind. Anyway, I had to just remove the offending piece just to gain relief for the area without completing the partial nail avulsion. I later attempted again when there was less to no visible infection - still no luck. Parent & child were not keen on the G.A option. The young individual has now taken heed of parent’s (& my) instructions to not pick at the nail... nail is now behaving itself.

    I then at a later time saw the grandmother of this individual & whilst talking about an unrelated topic she mentioned to me that she did not respond to Lignocaine. Hence I suspected a genetic link to possible insensitivity to Lignocaine... of which I have in the past found some papers on... even this Wikipedia link briefly discusses it.
  12. SueM

    SueM Welcome New Poster

    Hi Dennis ,how are you ?
    I am one of those people that local just doesn't take and have spoken to anaesthetist after spinal blocks and epidurals did not work. He also reasoned that this happens and could not tell me why. You may find that general is the only way
    Regards to all in SA
    Sue Moolman
  13. wdd

    wdd Well-Known Member


    When you say that LA doesn't work for you, does that mean that you get some anaesthesia, as in Dennis' case, where 'only half of the toe was numb' or does it have no effect at all on you?

  14. SueM

    SueM Welcome New Poster

    Hi Bill
    The local had no effect,after having an epidural and a spinal block I could still walk around ,this certainly explains why I hated the dentist growing up
  15. wdd

    wdd Well-Known Member

    Hi Sue,

    I know it probably sounds a silly question but, even though you could walk around after the epidural and spinal block, if someone had stuck a needle in your leg would it have been painful?

  16. SueM

    SueM Welcome New Poster

    Hi Bill
    This occurred while I was trying to have a Caesarian and I certainly felt them start to cut and ended up having a general. I always feel at the dentist but maybe the sensation is slightly dulled

  17. Ian Drakard

    Ian Drakard Active Member

  18. Mr C.W.Kerans

    Mr C.W.Kerans Active Member

    One experience of incomplete anaesthesia - big chap, had a bad motorbike spill - his left ankle was screwed and plated everywhere - I was using 3% Mepivacaine Plain for a left total nail avulsion. Scary when you pass the point of no return and must continue with the procedure.
  19. DTT

    DTT Well-Known Member

    Lignocaine doesn't work on me either. I spent much of my life in dental surgeries being put under extreme pain and being told by the sadistic dentist "you cant possibly feel this" Oh but I could, every bit. The pain wasn't even dulled :eek:

    I've been to a new dentist recently and explained. She gave me a choice of LA including 3% Mepivacaine plain which I chose and yes pain free dentistry at last.
  20. JaY

    JaY Active Member

    I would second this anatomical variation because although I have not experienced this before, I know it happens frequently to dentists who cannot locate a very posterior nerve near the molar regions (my dad in point).

    Mr Rehbock, doing GA on your patient just makes me think of doing the surgeries at the varsity's clinic...too stressful!
  21. hill

    hill Active Member

    Hi Dennis
    Hope you are well. Its been a while. I had a teenage patient recently with a similar problem. I work in a busy clinic and was sent a patient by his g.p when the gp could not get the hallux anaesthetised, despite a few top ups. I was also doing a NWR on him, also using 3% mepivicaine, and I kept on taking him in between other patients and topping up, giving enough time for the local to take in between patients etc. It was not happening. Then after a while of the usual injections at the base of the toe, I injected directly into the area at the base of the nail and after a few more minutes it was totally anaesthetised. It took quite a while, but because I was busy with other patients inbetween, it did not matter to me.

    Good luck and regards to everyone in S.A
    (Hillel Gluch-kerhill@gmail.com)
  22. toughspiders

    toughspiders Active Member

    Red head? :)
  23. Thank you all for the interesting ideas. I am just going to go the GA route. Then I do not have to even talk to the patient while doing it.
    Thanks you guys and girls

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