What is the recommended dosage and administration of lidocaine (local anesthetic) for a patient?

Lidocaine Dosing and Administration for Patients

Maximum Safe Doses by Route of Administration

For local infiltration and topical anesthesia, use a maximum of 4.5 mg/kg (not exceeding 300 mg total) without epinephrine, or 7.0 mg/kg (not exceeding 500 mg total) with epinephrine. 1, 2

Local Infiltration and Regional Anesthesia

• Without epinephrine: Maximum 4.5 mg/kg, absolute ceiling of 300 mg 1, 2
• With epinephrine: Maximum 7.0 mg/kg, absolute ceiling of 500 mg 1, 2
• Calculate dose using ideal body weight for obese patients (BMI >30 kg/m²): Men = height(cm) - 100; Women = height(cm) - 105 3, 1

Airway Topicalization

• For awake intubation and bronchoscopy: Maximum 9 mg/kg of lean body weight 1
• Transtracheal injection: 2-3 mL (80-120 mg) injected rapidly during inspiration 2
• Oropharyngeal spray: 1-5 mL (40-200 mg), combined with transtracheal should not exceed 5 mL (200 mg) total 2

Retrobulbar Injection

• Recommended dose for 70 kg adult: 3-5 mL (120-200 mg), equivalent to 1.7-3 mg/kg 2

Intravenous Infusion (Perioperative Analgesia)

• Loading dose: 1.5 mg/kg over 10 minutes (never as bolus) 4, 3, 1
• Maintenance infusion: 1.5 mg/kg/hour intraoperatively, reduce to 1.33 mg/kg/hour postoperatively 3, 1
• Absolute maximum: 120 mg/hour regardless of patient weight 4, 3
• Minimum patient weight: Do not use IV lidocaine in patients <40 kg 4, 3
• Maximum duration: Limit to 24 hours; if continuing beyond 24 hours, reduce rate by 50% due to prolonged half-life (increases from 100 minutes to 3.22 hours) 3

Topical Preparations

• 4% lidocaine cream/gel: Optimal anesthetic effect at 35-40 minutes without occlusion 5
• 5% lidocaine patches: Safe to use up to 4 patches in 24 hours, maintaining plasma levels <5 µg/mL 6

Pediatric Dosing

• Without epinephrine: Maximum 1.5-2.0 mg/kg 6
• With epinephrine: Maximum 3.0-4.5 mg/kg 6
• For children <10 years, apply Clark's rule or similar pediatric formula (e.g., 5-year-old, 50 lbs = 75-100 mg maximum) 2

Critical Safety Requirements

Cumulative Dose Monitoring

Always calculate the total cumulative dose from ALL routes of administration (infiltration, topical, nerve blocks, IV) to prevent toxicity. 1, 6

Timing Restrictions with Other Local Anesthetics

• Do not start IV lidocaine within 4 hours of any nerve block, fascial plane block, or port site infiltration 4, 3
• Do not perform nerve blocks until 4 hours after stopping IV lidocaine infusion 4, 3
• Remove topical lidocaine patches before starting IV lidocaine 4, 6
• Single-shot spinal anesthesia is acceptable due to small doses used 4

Monitoring Requirements for IV Administration

• Continuous ECG monitoring, pulse oximetry, and blood pressure every 5 minutes during initial infusion 4, 3
• Anesthesiologist must be present for loading dose administration 4, 3
• Use dedicated IV cannula for lidocaine infusion 3
• Have lipid emulsion 20% immediately available for toxicity treatment 3

Relative Contraindications

Exercise extreme caution or avoid in patients with: 4, 6

• Cardiac disease or arrhythmias
• Electrolyte disorders
• Seizure disorders
• Hepatic or renal impairment (contraindicated in advanced liver failure due to decreased clearance) 6
• Pregnancy/breastfeeding
• Neurological disorders
• Weight <40 kg (for IV use) 4, 3

Recognition and Management of Toxicity

Toxic Plasma Concentrations

• Early toxicity: 5-10 µg/mL 6
• Severe toxicity: >10 µg/mL 6
• Lethal range: 9-10 µg/mL and above 3

Early Warning Signs (Plasma 5-10 µg/mL)

• Circumoral numbness or tingling lips/tongue 4, 1, 6
• Tinnitus (ringing in ears) 4, 1
• Metallic taste 1
• Lightheadedness or dizziness 4, 1
• Slurred speech 4, 1
• Facial flushing or tingling 4, 6

Severe Toxicity Signs (Plasma >10 µg/mL)

• Muscle twitching or contractions 4, 1
• Loss of consciousness 4, 1
• Seizures/convulsions 4, 1
• Respiratory arrest 4, 1
• Cardiac arrhythmias 4, 1
• Myocardial depression 4, 1
• Ventricular arrest 4, 1

Immediate Management

• Stop all lidocaine administration immediately 1, 6
• Provide airway support and oxygen 1
• Treat seizures with benzodiazepines 1
• For cardiovascular collapse: administer lipid emulsion therapy 3, 1

Factors Increasing Toxicity Risk

• Acidemia (increases free drug dissociation from plasma proteins) 3
• Hypoalbuminemia or protein depletion 3
• Low skeletal muscle mass (reduces drug reservoir) 3
• Using actual body weight instead of ideal body weight in obese patients 3
• Concurrent beta-blockers (reduce lidocaine metabolism) 3
• Concurrent amiodarone (decreases clearance) 3
• Cytochrome P450 inhibitors or inducers 3

Useful Conversions

• 1% lidocaine = 10 mg/mL 1
• 2% lidocaine = 20 mg/mL 1

Special Considerations

Informed Consent

Obtain explicit informed consent when using IV lidocaine, explaining limited clinical benefit in most patients, risks of toxicity, and expected sensations (euphoria, facial flushing) 4, 3

Institutional Requirements

• Hospital medication governance committee approval required before implementing IV lidocaine protocols 3
• Only consultant anesthesiologists/intensivists experienced with IV lidocaine should initiate therapy 4
• Ensure entire team is competent and aware of local guidelines 4