Makindo Medical Notes

💊 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.