Local anaesthesia in skin surgery
LA · infiltration anaesthesia · regional / field block · ring block
Local anaesthesia is the cornerstone of skin-oncology surgery. Lidocaine (commonest), bupivacaine (long-acting), prilocaine and levobupivacaine are common agents; vasoconstrictors are used where appropriate to reduce bleeding and systemic absorption. Safe practice requires understanding of maximum doses, onset / duration, technique selection (infiltration, ring block, field block, regional block), adrenaline contraindications and toxicity recognition. Association of Anaesthetists LAST guidance and BSDS surgical-practice materials underpin good practice.
Agents
| Agent | Onset | Duration plain | Duration with vasoconstrictor | Max dose plain | Max dose with vasoconstrictor |
|---|---|---|---|---|---|
| Lidocaine 1-2% | 2-5 min | 30-60 min | 2-6 h | 3 mg/kg (max 200 mg) | 7 mg/kg (max 500 mg) |
| Bupivacaine 0.25-0.5% | 10-15 min | 4-8 h | 8-16 h | 2 mg/kg (max 150 mg) | Do not routinely increase above plain maximum; follow current BNF / SmPC / local policy. |
| Prilocaine 1-2% | 3-5 min | 30-90 min | 3-8 h with felypressin | 6 mg/kg (max 400 mg) | With felypressin: 8 mg/kg (max 600 mg). |
| Levobupivacaine 0.25-0.5% | 10-15 min | 3-6 h | Variable | 2 mg/kg (max 150 mg) | No routine dose increase; follow current BNF / SmPC / local policy. |
Quick conversion: 1% solution = 10 mg/mL. So 20 mL of lidocaine 1% = 200 mg (≈ max plain dose for a 70 kg adult).
These are typical adult maximum-dose guardrails used in UK skin surgery; always use the current BNF / SmPC, local policy and the lower safer dose in frail, elderly, low-body-weight, pregnant, hepatic / renal impairment or highly vascular-site cases. Toxicity is additive if local anaesthetics are mixed.
Adrenaline (epinephrine): typically 1:100 000 (10 µg/mL) or 1:200 000 (5 µg/mL). Onset 3-5 min for vasoconstriction; reduces bleeding and prolongs anaesthesia.
Technique
- Infiltration: subcutaneous injection in plane of intended excision; aspirate before injection to avoid intravascular.
- Field block: peripheral ring of injections encircling the lesion; useful for larger lesions and where direct infiltration distorts anatomy (e.g. eyelid, nasal tip).
- Ring block: digital nerve block at base of finger / toe; avoid adrenaline historically; modern evidence supports adrenaline safe in healthy digits.
- Regional / nerve block: supraorbital, infraorbital, mental, great auricular, transcutaneous mental.
- Tumescent: large-volume dilute lidocaine + adrenaline (separate monograph).
- Tips to reduce pain of injection:
- Warm solution to body temperature.
- Buffer with 8.4% sodium bicarbonate 1:10 ratio (raises pH; reduces sting).
- Use fine 27-30G needle; slow injection.
- Distraction; counter-pressure.
Adrenaline considerations
- Benefits: vasoconstriction (less bleeding, better field), prolongs anaesthesia, reduces systemic absorption (allowing higher max LA dose).
- Cautions:
- Severe cardiovascular disease (uncontrolled hypertension, recent MI, unstable arrhythmia) — discuss with cardiology.
- Phaeochromocytoma — avoid.
- MAOI / TCA: limit dose due to potentiation.
- Avoid in cocaine intoxication.
- End-arteries / appendage debate: historical avoidance in digits, nose tip, earlobe, penis. Modern evidence (Denkler 2001; Lalonde Dalhousie series) supports safety with 1:100 000 in healthy digital surgery; rebound vasodilatation possible. Use with care in patients with peripheral vascular disease, Raynaud, smokers.
Local anaesthetic systemic toxicity (LAST)
- Caused by inadvertent intravascular injection or absolute / relative overdose.
- Risk factors: high total dose, vascular sites, infiltration of inflamed / vascularised tissue, hepatic / renal impairment, pregnancy, neonates, elderly.
- Early symptoms (CNS): perioral tingling, metallic taste, tinnitus, light-headedness, dysarthria, visual disturbance, agitation.
- Late symptoms (CNS): tonic-clonic seizures, coma.
- Cardiovascular: hypotension, bradycardia, ventricular arrhythmias, cardiac arrest — bupivacaine particularly cardiotoxic.
- Management:
- Stop injection; airway / breathing / circulation; 100% O2.
- Treat seizures: benzodiazepine.
- Cardiac arrest: ALS algorithm; avoid lidocaine (already toxic) and vasopressin.
- Lipid emulsion 20% (Intralipid) 1.5 mL/kg bolus then 0.25 mL/kg/min infusion — AAGBI / ASRA guideline.
- Every clinic that uses LA should have Intralipid and AAGBI LAST algorithm immediately available.
Practical points
- Document agent, concentration, volume, total milligrams given, and time.
- Calculate maximum dose per kg before drawing up.
- Allow full onset before incision: lidocaine 2-5 min plain, 5-10 min with adrenaline for full vasoconstriction.
- Avoid mixing local anaesthetics in routine practice (additive toxicity).
- Confirm patient has not eaten heavily if planning IV sedation.
- For paediatric / anxious patients: topical EMLA / tetracaine pre-needle.
- Pregnancy: lidocaine is commonly used when local anaesthesia is required; use the lowest effective dose and seek obstetric / anaesthetic advice for complex or high-volume cases.
References
- Becker DE, Reed KL. Local anesthetics: review of pharmacological considerations. Anesth Prog. 2012;59:90-102.
- Association of Anaesthetists. Management of severe local anaesthetic toxicity 2023. London: Association of Anaesthetists; 2023.
- Denkler K. A comprehensive review of epinephrine in the finger: to do or not to do. Plast Reconstr Surg. 2001;108:114-124.
- British Society for Dermatological Surgery. Annual Surgery Workshop Manual. London: BSDS; 2024.
Spot a correction?
If any clinical statement, citation or link on this page needs updating, please email admin@skinoncology.net with the page name, the proposed correction and the supporting source.