Local anaesthetic - quick reference (ED)
This concise ED‑focused guide summarises common local anaesthetics, practical uses, key precautions and the immediate management of local‑anaesthetic systemic toxicity (LAST). It is intended for procedural planning and safe practice; final mg/kg calculations and absolute limits must be checked against your local trust formulary, BNF/SPC and anaesthetic advice (RCEM, Resuscitation Council UK).
Key principles
- Local anaesthetics are either amides (e.g. lidocaine, bupivacaine, prilocaine) or esters (e.g. tetracaine, benzocaine). Esters more commonly produce contact hypersensitivity via PABA metabolites; amides are metabolised hepatically.
- Toxicity results from excessive total dose, rapid systemic absorption or inadvertent intravascular injection. Early CNS features (perioral numbness, tinnitus, visual disturbance, agitation, seizures) may precede cardiovascular collapse (arrhythmia, conduction block, hypotension, cardiac arrest).
- Always calculate and document weight‑based dosing, total mg administered and planned maximum. Use incremental injection technique with frequent aspiration and monitoring.
- For major blocks or high doses ensure resuscitation kit, airway equipment and lipid emulsion are immediately available.
“Stop before you block” - pre‑procedure checklist (RCEM)
- Confirm patient identity, site and valid consent.
- Record patient weight and planned mg/kg dose.
- Review allergies and comorbidities (hepatic disease, cardiac disease, pregnancy).
- Ensure monitoring (ECG, NIBP, SpO2) and IV access as appropriate.
- Have oxygen, suction, airway kit, advanced airway equipment, emergency drugs and lipid emulsion immediately available.