Lidocaine Dosing for Knee Procedures
For knee procedures using local anesthesia, administer a maximum of 250 mg lidocaine with epinephrine (25 mL of 1% lidocaine with 1:100,000 epinephrine intra-articularly plus 40 mL of combined 1% lidocaine/0.25% bupivacaine for portal sites), which remains well below toxic thresholds and provides effective anesthesia. 1
Maximum Safe Dose Guidelines
The foundational dosing limits you must respect are:
- Without epinephrine: Maximum 4.5 mg/kg, not exceeding 300 mg total 2
- With epinephrine: Maximum 7.0 mg/kg, not exceeding 500 mg total 2
- For a 70 kg patient: This translates to 315 mg without epinephrine or 490 mg with epinephrine, though the absolute maximums of 300 mg and 500 mg apply 2
Practical Dosing for Knee Arthroscopy
Based on validated clinical protocols:
- Intra-articular injection: 25 mL of 1% lidocaine with epinephrine 1:100,000 (250 mg lidocaine) 1
- Portal site infiltration: 40 mL of combined solution (1% lidocaine with 0.25% bupivacaine) distributed across four arthroscopic portal sites 1
- Total lidocaine dose: Approximately 250-290 mg, which produces serum levels well within safe ranges at all time intervals measured (5,15,30,60, and 120 minutes post-injection) 1
This protocol has been used safely in over 500 cases without complications from the anesthetic agents 1.
Alternative Spinal Anesthesia Approach
For knee arthroplasty procedures, spinal anesthesia offers an alternative:
- Minidose lidocaine-fentanyl spinal: 20 mg of 0.5% lidocaine plus 20 mcg fentanyl intrathecally 3
- Motor blockade duration: Average 2.89 hours (range 1.73-5.17 hours) 4
- Time to ambulation: Average 0.58 hours from PACU 4
- This approach allows same-day discharge for outpatient knee arthroplasty 4, 3
Critical Safety Considerations
You must account for cumulative dosing from all sources:
- Do not administer lidocaine within 4 hours of any other local anesthetic intervention to prevent cumulative toxicity 2, 5
- Calculate the total dose of all local anesthetics administered regardless of route (infiltration, topical, nerve blocks) 2
- Remove any lidocaine patches before administering injectable lidocaine 2
Dose Adjustments for Special Populations
Reduce doses in the following circumstances:
- Body weight <40 kg: Use extreme caution or avoid 5
- Age >70 years: Reduce dose due to increased toxicity risk 5
- Hepatic impairment: Reduce dose significantly due to decreased clearance; contraindicated in advanced liver failure 5
- Renal dysfunction: Reduce dose for repeated or continuous administration 6
- Obesity (BMI >30 kg/m²): Calculate dose using ideal body weight, not actual body weight 5
Useful Concentration Conversions
Therefore, 25 mL of 1% lidocaine = 250 mg total dose.
Monitoring for Toxicity
Watch for early warning signs that appear at plasma concentrations of 5-10 μg/mL:
- Circumoral numbness or facial tingling 2, 5
- Tinnitus (ringing in ears) 2
- Slurred speech 2
- Metallic taste or tongue tingling 2
- Lightheadedness or dizziness 2
If any toxicity signs appear, immediately discontinue lidocaine administration, provide airway support, manage seizures with benzodiazepines, and use lipid emulsion therapy for cardiovascular collapse. 2
Technique Optimization to Reduce Toxicity Risk
- Always aspirate before and during each injection to avoid intravascular administration 7
- Inject slowly using incremental doses 7
- Add epinephrine 1:100,000 or 1:200,000 to reduce systemic absorption and extend duration 7, 1
- Consider buffering lidocaine with sodium bicarbonate to decrease injection pain 7
- Warm lidocaine to body temperature before injection 5
Emergency Preparedness
Before administering lidocaine for knee procedures, ensure availability of: