Lidocaine
Lidocaine
Lidocaine is a versatile medication used in pediatric emergency medicine, primarily as a local anesthetic and antiarrhythmic agent. It belongs to the Class IB antiarrhythmic drugs according to the Vaughan Williams classification.
- Generic Name: Lidocaine
- Brand Names: Xylocaine, Lidoderm
- Drug Class: Class IB antiarrhythmic, local anesthetic
- Available Forms: Injectable solution, topical preparations (gel, ointment, patch), oral solution
Mechanism of Action
Lidocaine exerts its effects through multiple mechanisms:
- As a local anesthetic:
- Blocks voltage-gated sodium channels in neuronal cell membranes
- Prevents the generation and conduction of nerve impulses
- As an antiarrhythmic:
- Decreases automaticity in Purkinje fibers and ventricular tissue
- Shortens the effective refractory period and action potential duration
- Increases the ventricular fibrillation threshold
Indications
In pediatric emergency medicine, lidocaine is used for:
- Antiarrhythmic indications:
- Treatment of ventricular arrhythmias, especially in the setting of acute myocardial ischemia
- Management of hemodynamically stable ventricular tachycardia
- Suppression of premature ventricular contractions (PVCs)
- Local anesthetic indications:
- Topical anesthesia for minor procedures (e.g., IV insertion, lumbar puncture)
- Infiltration anesthesia for suturing or incision and drainage
- Nerve blocks for pain management
- Other indications:
- Analgesia for burns (topical application)
- Management of refractory status epilepticus (in some protocols)
Dosage and Administration
Dosing in pediatrics varies based on the indication and route of administration:
- Antiarrhythmic dosing (IV):
- Loading dose: 1 mg/kg (maximum 100 mg) given over 5-10 minutes
- Maintenance infusion: 20-50 mcg/kg/minute
- Local anesthetic dosing:
- Maximum dose for infiltration: 4-5 mg/kg of 1% or 2% solution (without epinephrine)
- With epinephrine: maximum dose can be increased to 7 mg/kg
- Topical anesthetic dosing:
- LET (Lidocaine-Epinephrine-Tetracaine) gel: Apply to intact skin, maximum area 10 cm²
- EMLA cream (2.5% lidocaine, 2.5% prilocaine): Apply 1-2 g/10 cm², maximum 10 g
Adverse Effects
Lidocaine can cause several side effects, particularly at high doses or with rapid administration:
- Central Nervous System:
- Dizziness, lightheadedness
- Paresthesias, numbness
- Confusion, disorientation
- Seizures (at toxic levels)
- Cardiovascular:
- Hypotension
- Bradycardia
- Cardiac arrest (rare, usually with excessive doses)
- Respiratory:
- Respiratory depression (with high systemic levels)
- Allergic reactions:
- Rare, but can include anaphylaxis
- Local reactions:
- Pain or burning at injection site
- Tissue necrosis (with inadvertent intra-arterial injection)
Precautions and Considerations
- Cardiac monitoring: Continuous ECG monitoring is essential during IV administration for arrhythmias
- Hepatic impairment: Reduce dosage in patients with liver dysfunction, as lidocaine is primarily metabolized in the liver
- Seizure threshold: Use with caution in patients with a history of seizures, as lidocaine can lower the seizure threshold at high doses
- Cross-sensitivity: Patients allergic to other amide-type local anesthetics may also be allergic to lidocaine
- Methemoglobinemia: Rare but serious complication, particularly in infants under 6 months. Monitor for cyanosis unresponsive to oxygen
- Drug interactions:
- Beta-blockers: May increase lidocaine levels
- Cimetidine: Can decrease lidocaine metabolism
- Local anesthetic systemic toxicity (LAST): Be aware of signs and have lipid emulsion therapy available for treatment
- Epinephrine-containing preparations: Use with caution in areas with end-arterial circulation (e.g., fingers, toes, nose, ears)
