# Local Anaesthesia

## Overview

This module describes how to inject local anaesthesia using either a dental syringe or a

disposable needle and syringe

disposable needle and syringe

Useful to rule out intravascular injection via aspiration, or when a dental syringe is not available or accessible.

.

## Indications

1. Anaesthesia for minor procedures such as suturing

## Contraindications

1. Known allergy to local anaesthetic

## Patient information & consent

Always verify your patient’s identity and obtain informed consent before proceeding.

### How do I explain this procedure?

“I am going to give you an injection into the wound area that will make it numb.”

### What can my patient expect?

“This injection will sting, but after a few minutes you will not feel any pain from the wound. You may still feel me moving and touching there while I work in the area, but it will not hurt. The numbness will go away in a few hours.”

### What is my patient’s role?

“Let me know if you have any allergies. Fearing blood or needles is normal, but tell me if you have fainted from it. Stay very still while I give this injection.”

## Preparation

Prepare a trolley with equipment.

### Documentation

1. Patient notes

### Equipment

1. Sterile gloves
   Sterile gloves

   Although it is considered best practice to use sterile gloves to perform minor procedures, there is mounting evidence that infection rates are similar for sterile and non-sterile glove use.

2. Alcohol-based hand rub

3. Sharps container
   Sharps container

   If a sharps container is not within arm's length, use a kidney dish or other hard container to temporarily hold used sharps and to carry them to the sharps container for disposal.

4. Skin disinfectant
   Skin disinfectant

   Commonly used preparations include 0.5-2% chlorhexidine in 70% alcohol (Steriprep), or 10% povidone iodine. There is no consensus on the superiority of one agent above another. Caution: chlorhexidine solutions may be associated with burns and skin breakdown in infants < 2 months old.)

5. Sterile pack containing dental syringe

6. Dental needle

7. Lignocaine cartridges (1-2% lignocaine usually with adrenaline) — check for expiry

If no dental syringe/needle/lignocaine cartridges:

1. Non-sterile gloves
   Non-sterile gloves

   Although it is considered best practice to use sterile gloves to perform minor procedures, there is mounting evidence that infection rates are similar for sterile and non-sterile glove use.

2. Alcohol-based hand rub

3. Sharps container
   Sharps container

   If a sharps container is not within arm's length, use a kidney dish or other hard container to temporarily hold used sharps and to carry them to the sharps container for disposal.

4. Aspiration needle (preferably blunt fill)

5. Disposable needle and syringe

6. Alcohol swabs

7. An ampoule or vial of lignocaine — check for expiry

## Site & Positioning

Ask the patient to sit or lie with the area exposed and within easy reach.

The principle is to pierce the skin as few times as possible, but to infiltrate the entire area with local anaesthetic.

## Procedure

Follow medical asepsis with sterile gloves.

1. Perform hand hygiene.

2. Calculate the maximum

   safe dose
   safe dose

   Lignocaine without adrenaline: 3 mg/kg.
   Lignocaine with adrenaline: 6 mg/kg.

   A 2% lignocaine cartridge contains 1.8 ml, which is 36 mg of lignocaine. A 60 kg patient can receive 420 mg of lignocaine with adrenaline (maximum of 11 cartridges), or 180 mg of lignocaine without adrenaline (maximum of 5 cartridges).

   of local anaesthetic for this patient.

3. Open the sterile pack, creating a sterile field. Rearrange items in the pack using spare sterile forceps or gauze if necessary so the bowl is exposed. Place the spare forceps/gauze off the field.

4. Pour skin antiseptic into the bowl. Drop unsterile lignocaine cartridges and dental needle into the bowl, and open any sterile supplies needed for the procedure to follow onto the sterile field.

5. Don gloves.

6. Clean and drape the area required using skin disinfectant and gauze.

7. Dry the dental needle and lignocaine cartridges with gauze.

8. Twist the shorter section of the dental needle cap off and screw it onto the end of the dental syringe, needle facing into the barrel.

9. Withdraw the plunger all the way, then

   hinge
   hinge

   the back of the syringe at 90° to expose the barrel.

10. Load a cartridge, metal-edged cap first, into the barrel. Realign the syringe back into place.

11. Twist to uncap the needle.

12. Depress the plunger to squeeze a few drops of lignocaine from the needle.

13. Insert the entire needle under the patient’s skin, tracking just under the skin surface. You would usually advance from a wound corner along one edge of the wound.

14. Start injecting lignocaine while slowly withdrawing the needle back to the starting point to infiltrate the entire area along the length of the needle.

15. Stop just before you exit the skin. Advance the needle again, this time along the other edge of the wound.

16. Inject while slowly withdrawing again, until you exit the skin.

17. You may need to repeat this from the other corner of the wound if it is a long wound, or even more than once.

18. When you finish a cartridge, hinge open the syringe, remove the cartridge, replace it with another, and continue injecting.

19. Wait 5-10 minutes. To test if the anaesthetic has worked, grip the edge of the wound with toothed forceps and ask the patient if it is painful.

20. Twist off the needle and dispose of it in a sharps bin.

21. You may now proceed with the procedure required.

For disposable needle and syringe method, omit steps 3 to 12, as well as step 18. Follow the same method of injecting, but aspirate prior to injecting the anaesthetic.

## Troubleshooting

My patient is still feeling pain.

Make sure you wait a full 10 minutes before testing the patient’s sensation. If there is still pain, make sure you injected enough lignocaine into the entire area. Check the lignocaine expiry date. Local infection can also reduce the effectiveness of local anaesthetics. Rarely, some patients may be resistant to local anaesthetics.

The plunger of the dental syringe won’t depress

Recap the needle using a no touch technique first. Hinge open the syringe and check that the plunger is connected properly. In some very old syringes, rust may have collected. Sometimes removing and reinserting the cartridge helps. If this fails, use another dental syringe or a disposable needle and syringe

## Risks

1. Bleeding, bruising, and pain at the site

2. Allergic reaction to local anaesthetic or skin antiseptic

3. Sharps injury to healthcare personnel

4. Infection of the puncture site

5. Intravascular injection with systemic toxicity

6. Fainting

## References

1. Oxford Medical Education. Local Anaesthetic and anaesthesia. 2015. Available at: https://oxfordmedicaleducation.com/surgery/local-anaesthetic-and-anaesthesia/.

2. Finsen V. Nekrose i fingre og tær etter lokalbedøvelse med adrenalin--en vandrehistorie? [Necrosis in fingers and toes following local anaesthesia with adrenaline--an urban legend?]. Tidsskrift for den Norske laegeforening : tidsskrift for praktisk medicin, ny raekke. 2013;133(17):1827–1830.