Introduction
- Ask the patient about any prior adverse reactions to local anaesthesia.
- If the patient indicates that they cannot tolerate local anaesthesia, determine which type of anaesthesia is responsible for the allergy.
- Do not give more than the maximum allowed dose of local anaesthetic.
- Avoid intravasal injection.
- Be prepared for allergic or toxic reactions.
- Inject the fluid very slowly; this avoids unnecessary pain.
- If more than one injection is needed, try to administer subsequent injections in the area that is already anaesthetised.
Material
- Syringes 2 ml and 5 ml (the smaller the syringe, the greater the control when injecting liquid).
- Aspiration needle (low gauge needle).
- Fine needle with a length sufficient to reach halfway to the area to be anaesthetised.
- Local anaesthetic.
- Disinfectants.
- In medicine chest:
- Tavegil® 2 mg = 2 ml i.v.
- Dexamethasone 5 mg = 1 ml i.v.
- Epinephrine 1 mg = 1 ml, 0.3 ml i.m.
Procedure
- Tell the patient what you are about to do and ask if they are allergic to iodine.
- Ask the patient to lie down.
- Select your anaesthetic (lidocaine 0.5-1%, with or without epinephrine).
- Aspirate, depending on the size of the area to be anaesthetised and the amount of solution (5-10 ml).
- Mark the desired site of incision; some defects are no longer palpable after infiltration anaesthesia.
- Disinfect the area to be injected.
- Use the fine needle for infiltration.
- Position the needle at the point of entry.
- For wounds: Beyond the edges of the wound and in line with its longitudinal axis [Figure 9].
- For small tumours or skin lesions: On either side of the area to be removed, beyond the tumour
[Figure 10].
Figure 9
Figure 10
- Confirm by aspiration that the needle has not been inserted intravasally.
- Create a subcutaneous depot of local anaesthetic by injecting slowly (this can be achieved by advancing and pulling back the needle).
- First inject superficial subcutaneous areas (direction of the cutis) and then inject somewhat deeper.
- For excising or suturing wound margins, the subcutaneous depot should be created in the subcutis of the wound margins.
- For excising a tumour, injections should occur in a diamond-shaped pattern around the area to be excised (field block) [Figure 10].
- A depot is also created under the tumour; this will raise the tumour and make it more palpable and visible [Figure 11].
Figure 11
- Observe the patient for allergic or toxic reactions during the administration of local anaesthesia.
- Wait until pain stimuli are completely anaesthetised before beginning the surgery (the time to effect for lidocaine is 5 minutes).