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Local Anaesthetic (Amide) Pregnancy: Compatible — lidocaine widely used in obstetric regional anaesthesia

Lidocaine (IV — Regional Anaesthesia)

Brand names: Xylocaine

Adult dose

Dose: Infiltration: 1–5 mg/kg (plain) or up to 7 mg/kg (with adrenaline). Intravenous regional anaesthesia (Bier's block): 3 mg/kg (max 250 mg) of 0.5% solution in exsanguinated limb. IV lidocaine infusion (multimodal analgesia): 1.5 mg/kg loading over 10 min, then 1.5 mg/kg/h.
Route: Infiltration, IV, epidural, nerve block
Frequency: Single dose for nerve blocks; infusion for systemic analgesic use
Max: 5 mg/kg (plain); 7 mg/kg (with adrenaline)
LA systemic toxicity (LAST): treat with 20% Intralipid emulsion. High-risk zones for adrenaline-free LA: digits, penis, tip of nose, earlobe, flap reconstructions.

Paediatric dose

Dose: 3 mg/kg
Route: Infiltration or nerve block
Frequency: Single dose
Max: 5 mg/kg (plain); 7 mg/kg (with adrenaline)
Concentration: 0.5%, 1%, 2% solutions; 10 mg/mL for IV mg/ml
Neonates: maximum 2 mg/kg (reduced clearance). Children: same mg/kg as adults but calculate carefully by weight.

Dose adjustments

Renal

No dose adjustment for single dose; reduce infusion rate in severe renal impairment

Hepatic

Reduce dose in severe hepatic impairment — reduced metabolism

Paediatric weight-based calculator

Neonates: maximum 2 mg/kg (reduced clearance). Children: same mg/kg as adults but calculate carefully by weight.

Clinical pearls

  • LAST (Local Anaesthetic Systemic Toxicity): give 20% Intralipid 1.5 mL/kg IV bolus → 0.25 mL/kg/min infusion; repeat bolus if cardiac arrest persists. Stock Intralipid wherever LA used.
  • Adrenaline in LA: prolongs action and allows higher total dose; but absolutely avoid in end-arterial areas (digits, penis, flaps, nose tip, ear)
  • Bier's block (IVRA): tourniquet must remain inflated for minimum 20 min after injection to prevent bolus systemic absorption
  • IV lidocaine infusion for multimodal analgesia: evidence for reducing opioid consumption post-abdominal surgery

Contraindications

  • Complete heart block (without pacemaker)
  • IV injection into vascular area without cuff (Bier's block: must have double cuff correctly applied)
  • IV injection (unintended)

Side effects

  • CNS toxicity: perioral tingling, tinnitus, dizziness → seizures → coma (dose-dependent)
  • Cardiovascular toxicity: hypotension, bradycardia, arrhythmias → cardiac arrest (LAST)
  • Methaemoglobinaemia (rare, mostly with prilocaine/benzocaine)

Interactions

  • Other antiarrhythmics — additive cardiac effects
  • Fluvoxamine — increases lidocaine levels
  • Beta-blockers — potentiate cardiac depression

Monitoring

  • Signs of LAST (CNS and CV)
  • Pain and sensory block assessment
  • BP and ECG if IV infusion

Reference: BNFc; BNF; AAGBI LAST Guidelines 2010; ASRA Regional Anaesthesia Guidelines; Miller's Anaesthesia. Verify against your local formulary and the latest BNF before prescribing.

Related

Curated clinical cross-links plus same-class fallbacks.

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