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Maximum safe dose for nail surgery... calculation.

Discussion in 'General Issues and Discussion Forum' started by Mhairi Curle, Jul 23, 2013.

  1. Mhairi Curle

    Mhairi Curle Member

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    Hi can anyone tell me how to calculate the maximum safe dose of anaesthetic prior to carrying out nail surgery??

    Thanks Mhairi
  2. rosherville

    rosherville Active Member

    'can anyone tell me how to calculate the maximum safe dose of anaesthetic prior to carrying out nail surgery'

    I can, but first can you tell us where you trained and what you were taught re; LA ?
  3. BEN-HUR

    BEN-HUR Well-Known Member

    I could also tell you but the request is a bit on the vague side (hence more information is certainly required) thus I can understand why Mr Mason above asked his questions. With that aside, you haven't told us the type of agent (i.e. Lignocaine/Xylocaine 2%) you intend to use for the anaesthetic procedure. Then there is other important information as to the nature of the intended recipient i.e. age (child) & weight (as this can affect MSD levels between individuals). This important information should have been outlined within your studies... hence you may (should) have them in your notes... or give us more info & someone here will then likely help out or direct you in the right direction.
  4. W J Liggins

    W J Liggins Well-Known Member

    You COULD (emphasis, not shouting) use MMSD as a guide. If you did, then the dose would be far too high in my opinion. Per John Mason's post, why do you need to ask this?

    Bill Liggins
  5. Drslats

    Drslats Welcome New Poster

    What's wrong with you people answer the kids question.. 1%or 2% don't give more then 8cc's to a hallux, 1/2 for a lesser digit!!!!
  6. Craig Payne

    Craig Payne Moderator

    That is NOT based on an MSD!

    The MSD for lignocaine (no adrenaline) is ≈ 3 mg/kg
    So, for 70 kg adult, 210 mg is maximum dose = 21 ml of 1% solution

    Look up the MSD for the LA and do the maths.
  7. bob

    bob Active Member

    If you inject 21ml into a toe and it still not go numb or fall off - you are definitely in the wrong job.

    To the OP - here is a link to a site that should help: http://www.podiatrists-chiropodists...cal Anaesthesia/Local Anaesthetic Drugs 3.pdf

    As above, I assume you covered this at podiatry school? My recommendation would be to speak to your local podiatric surgery unit and ask to spend time shadowing there.

    Best of luck,
  8. Craig Payne

    Craig Payne Moderator

    That is the MSD! ... that does not mean that its practical.
  9. bob

    bob Active Member

    That's reasonable Craig - and 21mls in a popliteal block is not a great issue. In a toe (which is more relevant to the original post) it is clearly a problem! LOL!
  10. rosherville

    rosherville Active Member

    It would be nice if the questioner answered my initial query !

    As a profession it`s important to know what is currently being taught, or not taught. Too often we discover things being taught by academics that clearly have little relation to practical experience.

    I am involved in much medic-legal work and am still amazed at some of the 'cock-ups' inflicted on to patients by clinicians who are oblivious to their errors. 'That`s what I was taught' is no defence !
  11. BEN-HUR

    BEN-HUR Well-Known Member

    What the @#$%! is wrong with you 'Drslats'... reasoning has been provided as to the caution of answering (as you put it)... "the kids question" [sic]. There are real potential dangers in this "kid's" vagueness/ignorance which does not warrant an answer via this medium/context! It is disturbing... & I wouldn't feel comfortable providing such an answer in light of the original question (little background info & competence). What's probably more disturbing (& equally vague) is your answer (do you know what MSD is?), particularly in light of what I stated previously...

  12. wdd

    wdd Well-Known Member


    I would suggest that if you inject 21ml into a toe you are definitely in the wrong job whether or not it goes numb or falls off.

  13. wdd

    wdd Well-Known Member

    Dear Mhairi,

    The answer to your question is YES.

    I bet that by now you can calculate the MSD for every anaesthetic agent under the sun. How about answering your own question in this thread so that everyone can breath a sigh of relief?

  14. BEN-HUR

    BEN-HUR Well-Known Member

    I thought to do a Google search on this issue. Being that there was no mention of the intended anaesthetic agent for this "nail surgery" procedure I searched via the following... "maximum safe dose of local anaesthetic"... & came up with the following search results: http://www.google.com.au/#output=se...469,d.aGc&fp=fcee11b7ad46eb0&biw=1366&bih=620

    - The first result came up with the following: Maximum Recommended Doses and Duration of Local Anesthetics - from the university of Iowa, it outlines several anaesthetic agents (with or without Epinephrine/adrenaline), the calculations as well as the average weight of children at certain ages. However, it does state that for "lidocaine" (without Epinephrine/adrenaline) is 4 mg/kg - whereas (like Craig) I am informed it is 3 mg/kg.

    The first PDF citation within the above search is from a Podiatry source, in fact from Glasgow Caledonian University- which according to Mhairi Curle's profile (i.e. Glasgow, Scotland) is in the same neck of woods:

    - View attachment Local Anaesthetic Drugs 3.pdf

    This paper also cites several anaesthetic agents as well as the MSD calculations. This source however has lidocaine (without Epinephrine/adrenaline) at 3 mg/kg (with maximum body weight of 70 kg - hence MSD of 210mg; thus 21 ml of a 1% solution or 10.5 ml of a 2% solution).

    Thus Mhairi Curle, look into this issue a bit deeper (or get in contact with the author of the PDF for further insight).
  15. Paul Bowles

    Paul Bowles Well-Known Member

  16. horseman

    horseman Active Member

    I thought all the CPD I have to do for the HCPC was to avoid the above:confused: or am I being naive:sinking:
  17. horseman

    horseman Active Member

    Perhaps Mhairi Curle knows all this and needs some help with the actual math formula? If that's not it then I'd be concerned too:eek:
  18. davsur08

    davsur08 Active Member


    Maximum Safe volume = Percentage of the drug (1% or 2%) X Weight of the person/ 10 X safe dosage of the drug (3 for Xylocaine)

    MSD for 2% Xylo = 2 X 70/ 10 X 3 = 10.5 mLs.

    u can calculate MSD from the above formula.
  19. wdd

    wdd Well-Known Member

    Maybe it's just that Monday morning feeling but my own formula for MSV would be:

    MSV in ml = MSD in mg/kg x bodyweight in kg
    % x 10

    I have tried to get the % x 10 to line up under the dividing line on the right hand side of the equation but have had no success.

    Maybe that's what's written above and the difficulty of using x's and / for dividing is just obscuring things for me or maybe I've been overdosing patients for all these years? The truth is now revealed.

  20. davsur08

    davsur08 Active Member

    Sorry Bill

    MSV in mLs = Weight of the person (Kgs) × Percentage of the drug

    10 × Maximum Safe Dose of drug (Ex: 3 for Xylocaine)
  21. wdd

    wdd Well-Known Member

    Hi David,

    If we use your formula and the figures you gave in your worked example you get:


    that is

    which equals 4.67 and not 10.5?

  22. BEN-HUR

    BEN-HUR Well-Known Member

    The following may reduce the confusion:

    Based on Lignocaine (some call it Lidocaine. Brand name: Xylocaine) because this is the agent I use... & based on the 2% solution.

    - MSD for Lignocaine is 3mg per kg (however, there is a link in post # 15 which states 4mg/kg).

    - Now the 3mg/kg ratio is up to a point: 70kg max (within a 24 hr. period; I have also read a duration of action for Lignocaine is 90 - 200 minutes). Hence if one weighs beyond 70kg the MSD is still based on the 70kg MSD figure.

    - 1% Lignocaine contains 10 mg of Lignocaine per ml thus 2% Lignocaine contains 20 mg of Lignocaine per ml.

    *** Thus the calculations:
    70 (body weight in kg) X 3 (MSD of 3mg/kg for Lignocaine) = 210.
    210 divided by 20 (as there is 20mg per ml in a 2% solution) = 10.5.
    MSD = 10.5 ml. (thus 10.5 ml would also be the MSD for a 90kg person based on the 70kg limit max).​

    - For a child of 39 kg:
    39 (body weight in kg) X 3 (MSD of 3mg/kg for Lignocaine) = 117.
    117 divided by 20 (as there is 20mg per ml in a 2% solution) = 5.85.
    MSD for this child = 5.85 ml.

    Links in post # 15 has the calculations/MSD ratios for other anaesthetic agents... if Lignocaine isn't your choice.
  23. davsur08

    davsur08 Active Member

    body wt x msd / 10 x percentsge

    Sorry am not good at typing using phone key pad.
  24. W J Liggins

    W J Liggins Well-Known Member

    The last few posts beg the question. The OP asked the MSD for a digital block. As pointed out by John, Bill, Mark, Bob and self the MSD in that case is far less than the MMSD. Depending on any number of factors, including size of digit, chosen LA solution, presenting complaint etc. the dosage should be around 30-60mg. All really a matter of clinical judgement, hence the very valid query of why the question was posed in the first instance ie. is there some problem with clinical judgement here?

    Bill Liggins
  25. BEN-HUR

    BEN-HUR Well-Known Member

    Hence why the OP's query was stated as a bit vague. Hence why the OP was advised to provide more information &/or seek lecture notes or seek advice from a peer in person (i.e. lecturer/colleague)... as outlined in post 3 & post 12.

    Since then there was some confusion pertaining to calculations; post 23 was added to help clear that up (i.e. with a 2% Lignocaine solution). Of course other factors are potentially at play within one's personal clinical setting (i.e. nature of the recipient & toe)... where "clinical judgement" is made accordingly.

    Since post 1 there has been no further insight/information provided to help with the original query. Maybe the OP has sought out lecture notes or a peer (lecturer/colleague).
  26. wdd

    wdd Well-Known Member

    After the torrent of testoserone fuelled incredulity and derision 'the kid' has been subjected to I doubt that she will have the confidence to venture beyond her own front door for a week or two yet.

    However I think that you have misinterpreted the original question.

    What infact is being asked is, how much general anaesthetic could be inhaled by a surgeon, just before carrying out nail surgery, without falling to the ground or making a botch up or being sick over the foot?

    Obvious i'n'it!

  27. BEN-HUR

    BEN-HUR Well-Known Member

    Hmmm... I'm curious Bill, who are you referring to & how do you come to the above conclusion?
  28. wdd

    wdd Well-Known Member

    Hi Matt,

    I am not, of course, referring to all surgeons or all anesthetists but only to that sub-section who like to sniff their own gases. Even then, the the surgeons or anaesthetists who takes a quick gulp every now and again, just to convince themselves that they are a naughty boy/girl or that they have a darker side, are not included.

    The group that I am referring to is that smaller more competitive group of surgeons/anaesthetists who like to see just how far they can push things without being caught. In many ways this characteristic is similar to the professional athlete who ingurgitates his drug of choice before indulging in his particular form of brinkmanship.

    There competition is of course more complex and goes beyond the fear of being caught, it also involves seeing how far they can go before their performance breaks down to such an extent that someone suggests they should, go home for the day/week/year or take garden leave, early retirement or if they have really ruffled feathers high up in the hierarchy face disciplinary procedure.

    There you go, without naming names that should give you a better idea of whom I am referring to.

    As they say in paranoiogenic circles, 'You know who you are'.

    As to how I come to this conclusion I refer you to the penetratingly illuminating final paragraph in my previous post, "obvious i'n'it".

  29. wdd

    wdd Well-Known Member

    I wonder if the various, but exclusively male, response to Mhairi's initial request simply highlights the difference in male/female way of being?

    I liken it to driving and getting lost. My wife suggests that we stop and ask someone for directions. What is my response. A viceral contraction and a tacit response of over my dead body.

    What usually comes out of my mouth is, 'No, give me the map', ie let the competent man take over from the incompetent woman. What is going on in my head is that, if I have to ask, I am exposing my soft underbelly of fear of my own incompetence and failure. If I try to verbalise this my wife looks at me with wide eyed incomprehension.

    My sense is that Mhairi has done what most women would do first, ie ask their friends or more specifically ask their competent friends. Her error was that she didn't consider that the likelyhood was that the respondants would all be male, who, being confronted with someone asking for directions and not consulting the map herself, would almost certainly interpret it as a sign of probable incompetence and failure and would make them over focus on their own soft underbellies.

    Here I go, talking as a spokesman for the women when they can just as easily and with infinitely greater insight and knowledge speak for themselves.

  30. blinda

    blinda MVP

  31. wdd

    wdd Well-Known Member


    The Youtube video demonstrates beautifully other features of threatened male dominance with respect to women.

    Even the fact that it is easier/safer for women to approach the subject indirectly through what is largely male designed humour speaks volumes.

  32. blinda

    blinda MVP

    Male humour, you say?


    `Spose it explains why recently pts say "Has anyone ever told you, you look like that one from ABBA?"...must be the beard ;)
  33. BEN-HUR

    BEN-HUR Well-Known Member

    Bill, I asked the above question in an attempt to find out the reason & context of your above comment.

    You appear to have responded to the later part (not the first part) of the comment (i.e. pertaining to surgeons)... which appears to address issues you have noted with some surgeons & anaesthetists...

    Bill, I am confused by the areas highlighted in red. I still have no idea who you are referring to (let alone why you brought the issue up). I am also not aware of the word "paranoiogenic" (neither is the dictionary) - is it a play on words/spelling error? Subsequently not any wiser on your phrasing of "'You know who you are'".

    Also not familiar with the use of "i'n'it". Can you clear this issue up... up front, straight to the point without any ambiguity - thanks.

    I'll query you on the first part of the comment (in question) next...
  34. wdd

    wdd Well-Known Member

    Love the Harry Enfield sketches. Absolute genius.

    Where is he now?


    PS My reference to male designed humour was based on an assumption on my part that the sketches were largely created and written by men. Am I right or wrong? Don't know but if I was a betting man I'd put my money on it!

  35. BEN-HUR

    BEN-HUR Well-Known Member

    My original question still remains Bill (i.e. to the first comment) - who are you referring to & how do you come to the above conclusion?

    That aside, your latest input does now shed some light into your thinking. I'm not aware of the sex of the OP (is Mhairi a girl's name?). Is the OP a female? Also is the OP a child/young adult?... with now two references to Mhairi as a "kid" i.e. at post 6 by a first & (so far) only poster/contributor (i.e. 'Drslats') who registered at the time (July 2013)... & by yourself at post 27.

    If so, do you think it's appropriate to delve into these types of speculated (unfounded) issues on what some (if not many) consider a sensitive topic & subsequently disturbing conduct (sexism). Do you think it appropriate to take this thread down this path & incite what you seem to interpret as a sexist related attack on the OP? Do you think it appropriate to incite such conduct & accusations towards colleagues on what I thought was a professional academic forum?

    Whilst I have 'blinda' on my ignore list, your post did allude to a video... & whilst I am not logged in I do see those posts. Hence is that type of material pertaining to a sexist attitude towards woman (whether in the context of comedy or not - by either female or male) appropriate in the context of this discussion... particularly in light of what appears to be outrageous accusations towards contributors of this thread & the OP?

    The posts on this thread are here for all to see Bill; yes, there appears to be mainly males who have responded to this thread & subsequently to the OP (not sure of the sex of 'Drslats')... this is not uncommon on Podiatry Arena (i.e. more male contributors). Is the sex of the respondents an issue here? Does it matter - if so - why? Is the questioning of the little amount of information within the OP's initial query an issue here? Is the nature of the query - a potentially dangerous one (i.e. drug administration) which should warrant some concern in light of the limited information provided allowed to be questioned (regardless of the sex, age & education of the OP)? Is the sex & age of the OP an issue here? Did others find the comment/suggestion (at post 6) made by a first (& so far only) poster (i.e. 'Drslats', registering at the time) troublesome/inappropriate based on the limited information pertaining to the OP's query (i.e. unknown intended anaesthetic agent & unknown patient profile)?

    *** However, the above are just questions Bill (sincere questions - as a result of your previous vague response to my query & your latest input alluding to disturbing conduct)... without muddying the waters further I have refrained from jumping to conclusions - I will give you the opportunity to clear the air on this issue & make amends if required.

    Thank you.

    *** PS - if appropriate answers aren't forthcoming & subsequent resolution is not made - I will be bringing this issue up with the moderator.
  36. wdd

    wdd Well-Known Member


    The extremism of your interpretation of what I have written has so little to do with me that I will not respond to your vile nonsense as responding to it could be interpreted as giving it some validity.

    Now jump back into your big wooden toy and go and threaten somebody else.

    Yours sincerely,

  37. phil

    phil Active Member

    How could you inject too much LA into a toe?

    I mean, seriously. I barely use 4-5 mls ever. And 2-3 mls for children.

    If you're pumping the toe up like a balloon, you're doing something wrong.
  38. BEN-HUR

    BEN-HUR Well-Known Member

    Bill, your apparent interpretation & subsequent conclusion relating to the feedback provided to the OP has a lot to do with you... the following are your words... chosen to incite what appears to be sexism conduct at play... which entail have incited sexism related videos (regardless whether added in jest or not)... by another member who also seemed to interpret your words in such light (hence I'm not the only one)...
    ... I clearly outlined via the following that I was questioning you (not jumping to conclusions) on this (wanting to be as fair as possible), based on your above input & your vague (ambiguous) explanation to my first query of your above comment...
    The only "vile nonsense" (as you wish to put it) I can thus see so far has been your apparent vile accusations in inciting sexist conduct on this thread (within what should be a professional academic forum)... of which you now don't wish to clear the air on because you apparently choose to feel "threatened" by my questioning of it.

    Can I suggest Bill you muster up the courage to clearly explain your reasoning (as asked - without ambiguity & playing with words) & then if required, have the decency to apologise & retract such "vile nonsense" from this thread.

    Yours sincerely,
  39. BEN-HUR

    BEN-HUR Well-Known Member

    I have come close to the apparent MSD for the individual when there has been heavy infection present (not uncommon for ingrown nails)... hence one should be mindful of this. Then there was this recent thread which highlighted apparent insensitivity to anaesthetic agents... "Local anaesthetic not working"... which needs to be considered when dealing with a recalcitrant toe (as rare as this appears to be)... which will not anaesthetise.

    The occurrence of an MSD issue arising would normally be extremely small, yet needs to be considered in light of circumstances like the above. Hence the awareness of MSD & thus inclusion within the teaching syllabus... as well as I assume the reasoning for the start of this thread.

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