Local Anaesthetics for Suturing or other Procedures
💊 Drugs Used
- ⚡ Lidocaine (Lignocaine) – short acting
• 1% = 10 mg/mL → max 3 mg/kg (without adrenaline)
• 2% = 20 mg/mL → max 3 mg/kg (without adrenaline)
- ⚡ Lidocaine + adrenaline (1:200,000) → max 7 mg/kg
• Adrenaline reduces bleeding & prolongs block
- 🐢 Bupivacaine (Marcaine®) – long acting
• 0.25% (2.5 mg/mL) or 0.5% (5 mg/mL)
- 🐢 Levobupivacaine – safer cardiac profile
• Max ~2 mg/kg
🔬 Pharmacology
- Block voltage-gated sodium channels → prevents depolarisation → no action potential.
- Blockade affects small, myelinated fibres first (pain, temperature) → then larger fibres (motor).
- Adrenaline (low conc. 1:200,000): vasoconstriction ↓ absorption, ↓ toxicity, ↑ duration.
- ⚠️ Never use adrenaline in: penis 🚫, digits/ears/nose caution 🚫, skin flaps caution.
🛠️ Usage
- Dose by patient weight (mg/kg). Children, elderly, and liver disease patients at higher risk of toxicity.
- Most small wounds = 5–10 mL lidocaine (well within limits for adults).
- 1% = 10 mg/mL → calculate max dose before injecting.
- Infiltrate along wound edges; always aspirate before injecting to avoid intravascular dose.
- Use fine needle (27G) → less painful multiple injections.
⚠️ Local Anaesthetic Toxicity
- Often from overdose or intravascular injection.
- 🌀 CNS: dizziness, tinnitus, peri-oral paraesthesia, disorientation → seizures (tonic-clonic), coma.
- ❤️ CVS: bradycardia, hypotension, asystole, VF.
🚑 Management of Toxicity
- Call MET/Crash team immediately 📞.
- ABCDE: secure airway, 100% oxygen, IV access, BLS/ALS if needed.
- Intralipid 20%:
• Bolus 1.5 mL/kg IV over 1 min
• Then infusion 15 mL/kg/hour
• Repeat bolus if cardiac arrest persists (max cumulative ~12 mL/kg).
- Avoid high-dose adrenaline and lignocaine-containing antiarrhythmics (they worsen toxicity).
- Continue advanced life support until ROSC.
💡 Exam tip:
• Always calculate max safe dose before drawing up.
• Lidocaine max = 3 mg/kg (plain), 7 mg/kg (with adrenaline).
• Bupivacaine more cardiotoxic than lidocaine.
• Intralipid is the specific antidote.
