06.11.06

How to use local anaesthetic

Posted in Emergency Dept., General Practice, Michael Tam, Procedures, Surgery, Wards at 16:12 by Michael Tam

Original article by: Michael Tam :: Printer friendly

Local anaesthetic is one of the best inventions in medicine. It is difficult to imagine doing minor surgery, debridement, incision and drainage, repair of laceration, excisions, etc., without it, though we have only had infiltration local anaesthetics for about a century (with the creation of synthetic cocaine in 1891).

My first regular experience with infiltration local anaesthetics was in the emergency department. There was always a steady flow of people presenting with lacerations. At that time, I had always used whatever was available. However, there are some tricks to using “local”.

Where available and not contraindicated, use lignocaine 2% + 1:80,000 adrenaline

Simply, lignocaine 2% works better than lignocaine 1%. Adrenaline causes local tissue vasoconstriction, leading again to better and longer anaesthesia, and a less bloody field. Furthermore, as the adrenaline keeps the lignocaine in the local tissues longer, you are less likely to have systemic side-effects (meaning you can use more local anaesthetic).

Contraindications

  • Avoid higher concentrations of lignocaine in infants and children. Use plain lignocaine 1%;
  • don’t use adrenaline in areas with end arterial supply or else you risk tissue infarction – e.g., fingers, toes, nose, ears, penis;
  • avoid in people with known sensitivity to sympathomimetic amines (e.g., tachyarrhythmias);
  • avoid in pregnant women;
  • adrenaline is contraindicated in any intravenous regional anaesthetic technique.

Maximum dosage of lignocaine

Without adrenaline 3 mg per kg (body weight)
With adrenaline 7 mg per kg (body weight)
Lignocaine 1% = 1 g per 100 mL or 10 mg/mL

Lignocaine 2% = 2 g per 100 mL or 20 mg/mL
For the average 70 kg adult:
Lignocaine 1% can use up to 21 mL for infiltration safely
Lignocaine 1% + 1:100,000 adrenaline can use up to 49 mL for infiltration safely
Lignocaine 2% can use up to 10 mL infiltration safely
Lignocaine 2% + 1:80,000 adrenaline can use up to 24 mL infiltration safely

Caution must be used particularly with Lignocaine 2% without adrenaline as you can easily infiltrate up to (and over) 10 mL on a large laceration.

Technique tips

There isn’t really much to know about the “technique” of infiltrating local anaesthetic. However, you can try the following:

  • Use a syringe size appropriate to your volume of local anaesthetic: usually either a 5 mL or 10 mL syringe;
  • use a small 25 gauge hypodermic needle for superficial infiltration;
  • use a longer 23 gauge hypodermic needle for more extensive infiltration;
  • warn the patient that the initial injection of local anaesthetic is painful;
  • inject a small sub-dermal “bleb” and wait for 30-60 seconds to create a sentinel area of local anaesthesia before extending your infiltration;
  • lignocaine solution is acidic (pH 5-7 for plain and pH 3-4.5 with adrenaline) and some people suggest mixing a small amount of sodium bicarbonate solution to raise the pH (and reduce the pain) – I personally have never bothered with this;
  • advise the patient (and remember yourself) that the local anaesthetic will wear off in 1-2 hours. Prescribe a moderate strength analgesic if appropriate.

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5 Comments »

  1. Dr Charles Lee said,

    Wednesday 20 September, 2006 at 19:04

    Dear Michael,
    Please let me know where I can get the concentration of 1% lignocaine with 1:100,000 adrenaline- which company in Malaysia has this product. I have tried Astra etc but futile. I would appreciate some help to get this concentration urgently.

    Dr Charles Lee
    Plastic Surgeon
    Sabah Medical Centre

    Reply

  2. Michael Tam said,

    Thursday 21 September, 2006 at 0:30

    Dear Charles,

    Lignocaine 1% with 1:100,000 adenaline (Xylocaine) in 5 mL glass ampoules is widely available in Australia in pharmacies and medical supply companies. It is produced by AstraZenica.

    Unfortunately, I have absolutely no knowledge of where or if this is available in Malaysia.

    Sorry that I cannot be of more help.

    Reply

  3. Kinga Karlsson said,

    Friday 12 October, 2007 at 8:54

    Hi,

    I am 23 weeks pregnant, I had 2 moles removed the other day and i had locla anasthetics. They gave me a micture of lignocaine and adrenaline. I asked the doctor if it ok in pregnancy. His answer wasn’t quiet assuring. He looked it up in BNF where it was said it was contraindicated above 20ml. I can’t remember the exact name of the drug. after all he gave me the minimum dose (5ml).
    Is this correct or can it cause any complication to my baby.

    Please let me know if you know it.

    Thanks

    Kinga

    Reply

  4. dr.jyoti goswami said,

    Thursday 26 November, 2009 at 19:23

    why xylocain with adrenalin is contraindicated in hyperthyrodism?

    Reply

    • Michael Tam said,

      Thursday 26 November, 2009 at 19:33

      Giving someone adrenaline, a sympathomimic agent in uncontrolled hyperthyroidism would increase the risk of tachyarrhythmias.

      Reply

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