What is the recommended dosage and usage of lignocaine (lidocaine) in medical procedures?

Lignocaine (Lidocaine) Dosing and Administration

Maximum Safe Doses

The maximum safe dose of lignocaine without epinephrine is 4.5 mg/kg (not exceeding 300 mg total), while with epinephrine it increases to 7 mg/kg (not exceeding 500 mg total) in adults. 1, 2

Adult Dosing Limits

• Without epinephrine: 4.5 mg/kg (maximum 300 mg total) 1, 2
• With epinephrine: 7 mg/kg (maximum 500 mg total) 1
• For infiltration and nerve blocks, these limits must be strictly observed to prevent systemic toxicity 1, 2

Pediatric Dosing

• Children >3 years: Maximum 3 mg/kg for procedures like intravenous regional anesthesia 1
• Children 5 years/50 lbs: Should not exceed 75-100 mg (1.5-2 mg/lb) 1
• General pediatric rule: 1.5-2.0 mg/kg without epinephrine; 3.0-4.5 mg/kg with epinephrine 3
• Use more dilute solutions (0.25-0.5%) for intravenous regional anesthesia in children 1

Intravenous Lidocaine for Analgesia

For perioperative analgesia, administer 1.5 mg/kg (using ideal body weight) as a loading dose over 10 minutes, followed by maintenance infusion of 1.5 mg/kg/hour for maximum 24 hours. 4, 5

Critical Safety Requirements

• Calculate dose using ideal body weight, not actual body weight, especially in obese patients (BMI >30 kg/m²) 4, 3
• Never give as bolus—loading dose must be infused over 10 minutes 4
• Maximum infusion rate: 1.5 mg/kg/hour, not exceeding 120 mg/hour regardless of weight 4
• Do not use in patients <40 kg 4, 3
• Requires dedicated IV cannula 4
• Anesthesiologist must be present during loading dose 4

Monitoring Requirements

• Continuous ECG monitoring 4
• Pulse oximetry 4
• Regular blood pressure measurements 4
• Ideally managed in high dependency unit when used outside operating room 4
• Have 20% lipid emulsion immediately available for toxicity treatment 4, 3

Timing Restrictions with Other Local Anesthetics

• Do not administer within 4 hours of nerve blocks or other local anesthetic interventions 4, 3
• Do not perform nerve blocks until 4 hours after discontinuing IV lidocaine 4
• Remove topical 5% lidocaine patches before starting IV infusion 3
• Account for cumulative dose from all local anesthetic sources 3, 1

Cardiac Arrhythmia Dosing

For ventricular arrhythmias, give 1 mg/kg IV bolus (maximum 100 mg) over 2 minutes, with additional 0.5 mg/kg boluses every 5-10 minutes if needed, then maintain with 2-4 mg/min continuous infusion. 5

Alternative Arrhythmia Protocols

• Ventricular tachycardia with pulse: 50 mg IV over 2 minutes, repeated every 5 minutes to total 200 mg 5
• Maintenance infusion: 2-4 mg/min (20-50 µg/kg/min) once rhythm controlled 5
• All IV drugs for life-threatening arrhythmias must be followed by 20 mL saline bolus 5

Epidural and Regional Anesthesia

Epidural Dosing

• Dose varies by dermatomes: Generally 2-3 mL per dermatome of appropriate concentration 1
• Test dose mandatory: 2-3 mL of 1.5% lidocaine at least 5 minutes before full dose to detect subarachnoid placement 1
• If test dose contains epinephrine (10-15 mcg), watch for "epinephrine response" within 45 seconds (increased heart rate/blood pressure) indicating intravascular injection 1
• Maximum dosing interval: Do not repeat maximum dose at intervals <90 minutes 1

Specific Regional Techniques

• Retrobulbar injection: 3-5 mL (120-200 mg) for 70 kg adult 2
• Transtracheal injection: 2-3 mL, rarely exceeding 5 mL total (200 mg) 2
• Paracervical block: Maximum 200 mg total per 90 minutes, divided between both sides with 5-minute interval 1
• Intravenous regional anesthesia: Maximum 4 mg/kg in adults 1

Topical and Airway Anesthesia

• Laryngoscopy/bronchoscopy spray: 1-5 mL (40-200 mg), which is 0.6-3 mg/kg 2
• Lidocaine 5% patches: Maximum 4 patches for 12 hours on, 12 hours off 3
• Plasma levels remain safe with up to 4 patches in 24 hours 3

Pharmacokinetic Considerations Affecting Dosing

Time-Dependent Changes

• Half-life increases with infusion duration: 100 minutes for <12 hours, but 3.22 hours after 24 hours 4, 5
• After 24 hours, reduce infusion rate by 50% even without cardiac/hepatic failure 4
• In uncomplicated myocardial infarction, half-life exceeds 4 hours 5

Factors Increasing Toxicity Risk (Require Dose Reduction)

• Acidemia: Increases free drug by enhancing dissociation from plasma proteins 4
• Hypoalbuminemia: Increases free plasma concentration 4
• Low skeletal muscle mass: Reduces drug reservoir capacity 4
• Beta-blockers: Reduce lidocaine metabolism 4
• Amiodarone: Decreases clearance, especially problematic with prolonged infusions 4
• Advanced liver failure: Absolute contraindication for patches; dramatic dose reduction needed for IV 5, 3
• Cardiac failure or shock: Requires dramatic dose reduction 5
• Age >70 years: Higher toxicity risk 3
• Renal dysfunction: Increases toxicity risk 3

Toxicity Recognition and Management

Toxic Plasma Concentrations

• Therapeutic range: Up to 5 µg/mL 4, 5
• Toxicity threshold: 9-10 µg/mL 4, 5

Early Warning Signs (5-10 µg/mL)

• Perioral numbness and facial tingling 4, 5, 3
• Tinnitus and metallic taste 4, 5
• Slurred speech 3
• Light-headedness and dizziness 5, 3

Severe Toxicity Signs (>10 µg/mL)

• Drowsiness and confusion 5, 3
• Muscular twitching and tremor 5, 3
• Seizures 4, 3
• Loss of consciousness 3
• Respiratory arrest 3
• Cardiac arrhythmias and myocardial depression 3
• Cardiovascular collapse 4

Immediate Management

• Discontinue all lidocaine immediately if any toxicity signs appear 3
• Administer 20% lipid emulsion per local anesthetic systemic toxicity (LAST) protocol 4, 3
• Full resuscitation equipment must be immediately available 3

Techniques to Reduce Injection Pain

• Buffer with bicarbonate: Mix 1 part bicarbonate to 10 parts plain lidocaine 6
• Warm to body temperature (37°C): Significantly reduces injection pain 7
• Inject slowly with small-caliber needle 3
• Aspirate before and during each supplemental injection 3

Common Pitfalls to Avoid

• Using actual body weight instead of ideal body weight in obese patients leads to overdosing 4, 5, 3
• Failing to account for cumulative doses from multiple local anesthetic sources (topical, infiltration, nerve blocks) 3, 1
• Administering within 4-hour safety window of other local anesthetic interventions 4, 3
• Not having lipid emulsion immediately available before administration 4, 3
• Inadequate monitoring during IV infusions 4
• Exceeding 24-hour infusion duration without dose reduction 4