Technique is described in section “Skills.”
Necessary Equipment
Depending on the type of local anaesthesia selected (see “Skills”) the following must be present:
- 1 canister of ethyl chloride spray for freezing the skin prior to abscess incision.
- Syringes, 2 and 5 ml, with low-gauge needles for drawing up fluids and high-gauge needles for infiltration.
- Local anaesthetic with or without a vasoconstrictor.
- Medication for acute intervention in case of an allergic reaction to local anaesthetic or a toxic reaction due to absolute or relative overdose.
Local Anaesthetics
The local anaesthetics most widely used in general practice are lidocaine and prilocaine, 1% or 2%, with or without additional epinephrine (1:100,000). Adding a vasoconstrictor slows the resorption of the local anaesthetic, which prolongs its effects. The advantage of this approach is that the patient goes home without feeling pain. A secondary effect of vasoconstrictors is a reduced tendency for bleeding at the surgical site. However, this also increases the risk of infection.
Contraindications
Contraindications for the use of a local anaesthetic with additional epinephrine are:
- Application in an area containing terminal arteries, such as the fingers, toes, penis, end of nose, earlobes, or eyelids.
- Poor vascularisation (arteriosclerosis; diabetes mellitus).
- Coronary insufficiency.
- Arrhythmias.
- Hyperthyroidism.
Dose
For paediatric patients, the maximum dose is calculated based on body weight; the maximum dose of lidocaine without epinephrine is 4 mg/kg [Table 1]. For adults, the maximum dose is 200 mg without epinephrine and 500 mg with epinephrine.
The time to effect with lidocaine is 3-5 minutes. The duration of effect for lidocaine without additional epinephrine is 1 hour. The duration of effect for lidocaine with epinephrine is 2 hours. Prilocaine works faster than lidocaine (within 3 minutes) and its effects last longer (2 hours without additional epinephrine).
Lidocaine 1% without epinephrine |
20 ml (= 200 mg) |
Lidocaine 1% with epinephrine 1:100,000 | 50ml |
Lidocaine 2% without epinephrine |
10 ml (= 200 mg) |
Lidocaine 2% with epinephrine 1:100,000 | 25 ml |
Prilocaine 1% without epinephrine | 40 ml |
Prilocaine 1% with epinephrine 1:200,000 | 60 ml |
Prilocaine 2% without epinephrine | 20 ml |
Prilocaine 2% with epinephrine 1:200,000 | 30 ml |
Table 1
Adverse Effects
Reactions to local anaesthesia can be caused by the active agent itself or the added vasoconstrictor. Allergic reactions to the local anaesthetic itself may include:
- Skin reactions.
- Anaphylactic shock.
Management of Allergic Reactions
For skin reactions, administer an antihistamine by intravenous injection (e.g. 2 ml Tavegil®). For anaphylaxis, administer the following medication:
- 1 ampoule Tavegil® 2 mg = 2 ml i.v.
- 2 ampoules dexamethasone (Oradexon®) 5 mg = 1 ml i.v.
- 0.3 ml epinephrine 1:1000 (1 mg = 1 ml) i.m.
Epinephrine is available in ready-to-use automatic syringes (Epipen®), which provide a fixed dose of 0.3 mg.
Management of Toxic Reactions
Toxic reactions caused by local anaesthetics may include:
- Agitation, confusion.
- Visual or auditory disturbances, dysarthria.
- Sweating, vomiting.
- Fasciculations.
- Convulsions.
- Unconsciousness.
- Coma.
- Respiratory arrest.
These reactions can lead to excitation or depression of the central nervous system and are related to blood concentrations.
The systemic reactions that can occur due to lidocaine overdose must be managed symptomatically. The ABC rule applies here. If necessary, the resuscitation team at the hospital may be called. The general practitioner must call 112 in case of emergency.
There is no known antidote for lidocaine.
Toxic reactions caused by the vasoconstrictor can occur in the following situations:
a When epinephrine is inadvertently administered intravasally.
- Paleness.
- Agitation; shaking.
- Sweating.
- Tachycardia.
- Hypertension.
- Extrasystole.
- Ventricular fibrillation.
b When epinephrine is used in an area containing terminal arteries, extreme vasoconstriction can eventually lead to acral necrosis.
Management of Tachycardia
Tachycardia due to intravasally administered epinephrine is usually transient, because the half-life of epinephrine is short. While taking the patient’s pulse, wait a few minutes until the frequency decreases to 100/min. Administration of medication is not advised due to the hypotensive effect. Carotid massage is ineffective as long as the epinephrine
(a sympathomimetic) is in effect.
Management of Extrasystole
Intravenous injection of lidocaine should not be given for extrasystole in this instance, because the patient has already received lidocaine intravasally by accident.
Management of Ventricular Fibrillation
Switch to resuscitation if the patient loses consciousness and carotid artery pulsations are no longer palpable.