Local Anaesthetics
Examples
- Lidocaine
- Bupivacaine (& Levobupivacaine)
- Prilocaine
Indications
- Local Anaesthesia
- Nerve Blockade
- Plexus Blockade
- Regional (Neuraxial Blocks)
Contraindications
Contraindications
Cautions
- Injection into inflamed or infected tissues
- Middle ear injection
- Complete heart block
Cautions
- Impaired cardiac conduction / Cardiovascular disease
- Hypovolaemia / Shock
- Epilepsy
- Myasthenia Gravis
Mechanism
Local anaesthetics block initiation and propagation of action potentials in neurons around the site of administration. They do this by preventing a voltage-dependent movement of Na+ ions into the intracellular space by physically plugging the channel pore.
Co-administration with adrenaline results in local vasoconstriction, adrenaline binds α1-adrenergic receptors, preventing excessive leak of the anaesthetic into the systemic circulation.
Co-administration with adrenaline results in local vasoconstriction, adrenaline binds α1-adrenergic receptors, preventing excessive leak of the anaesthetic into the systemic circulation.
Administration
- Injection
- Topical (cream / gel)
Adverse Reactions
Minimal side effects are seen normally with local infiltration, but toxicity can occur with systemic availability (accidental IV administration, excessive doses or length of use). Hypersensitivity reactions are occasionally seen.
Other side effects are related to the site of administration and the nature of the block produced, for example sympathetic block caused by spinal anaesthesia or inadvertent phrenic nerve block during brachial plexus blockade.
Toxic effects are:
Other side effects are related to the site of administration and the nature of the block produced, for example sympathetic block caused by spinal anaesthesia or inadvertent phrenic nerve block during brachial plexus blockade.
Toxic effects are:
- Feeling of inebriation / light-headedness followed by drowsiness, blurred vision, nausea and vomiting, muscle twitching, tremors leading to respiratory failure, seizures and coma
- Hypotension and bradycardia
- Other arrhythmias and cardiac arrest can occur
Interactions
Nil of note.
Education
Ensure that adequate anaesthesia is achieved before undertaking any procedures.
Pharmacokinetics
Metabolism is primarily by the liver following entry of the drugs into the systemic circulation; the metabolites can be pharmacologically active. Most local anaesthetics have a local vasodilatory effect, enhancing their speed of entry into the systemic circulation and the associated risk of side effects- for this reason adrenaline is co-administered with larger doses of local anaesthetics. Remember adrenaline is not suitable for body appendages.
