Infiltration of Local Anaesthetic

Local anaesthetic is useful in many procedures, ranging from the excision of skin lesions or lipomas to aiding post-operative analgesia in major abdominal surgery.

Often local anaesthetic is used with adrenaline to decrease bleeding from the operation site and to increase the amount of local anaesthetic that can be used*.

*Remember that adrenaline must never be used in areas with an end-arterial supply, such as digits, the pinna, penis, or nose, as the vasoconstriction can cause ischaemia and gangrene of the area


Procedure

When administering local anaesthetic, the theory to bear in mind is to infiltrate around the whole planned surgical field, allowing the anaesthetic to act on the nerve endings that supply the area from all directions.

Before Starting

  • Check the expiry date and concentration of the anaesthetic. If the patient is awake, warm the anaesthetic in your hand, as this has been shown to significantly reduce the pain of injection.
  • Start with a fine bore needle. A subsequent change to a longer and wider needle can be used after initial infiltration once the injection site is numbed.

Methods of Infiltration

Two methods of infiltration can be performed, both with the aim to infiltrate subcutaneously:

  • Static – Insert the needle, aspirate to ensure no flashback of blood then inject (as shown in the video).
    • Inadvertent injection of local anaesthetic into the circulation can lead to paresthesia, light-headedness, cardiac arrhythmias, and cardiac arrest.
  • Continuous – Insert the needle, inject continuously into the surrounding area with continuous movement.

Aim to penetrate the skin as little number of times as possible. Rotate the angle of the needle to allow maximal infiltration through one puncture site. If required, additional punctures should be through an area already infiltrated.

Prior to any procedure, check that the area has been anaesthetised adequately by checking sensation, pinching using toothed forceps.


Maximum Dosage of Local Anaesthetic (Adults)

It is very important to know the safe dosage of local anaesthetic.  The table below is a guide but you should check local protocols before administering it. 

Anaesthetic Without adrenaline With adrenaline
Lignocaine 3mg / kg 6mg / kg
Bupivicaine 2mg / kg 2.5mg / kg

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