What is the recommended intravenous lidocaine infusion dosing regimen as an adjunct to general anesthesia for an adult patient without severe hepatic impairment, third-degree heart block, seizure disorder, or lidocaine allergy?

Intravenous Lidocaine Infusion as Adjunct to General Anesthesia

For adult patients undergoing major abdominal, pelvic, or spinal surgery without regional analgesia, administer an intravenous lidocaine bolus of 1.5 mg/kg (ideal body weight) over 10 minutes at induction, followed by continuous infusion at 1.5 mg/kg/hour intraoperatively, with discontinuation 30 minutes before emergence or within 24 hours postoperatively. 1, 2

Dosing Protocol

Loading Dose

• Calculate using ideal body weight (IBW), not actual weight, especially critical in obese patients (BMI >30 kg/m²): IBW = height(cm) - 100 kg for men, height(cm) - 105 kg for women 3, 2
• Maximum loading dose: 1.5 mg/kg IBW administered as a slow infusion over 10 minutes—never as a rapid bolus, which significantly increases toxicity risk 2, 4
• The French expert panel suggests a slightly higher range of 1-2 mg/kg for the bolus, though the more conservative 1.5 mg/kg maximum is safer 1

Maintenance Infusion

• Intraoperative rate: 1.5 mg/kg/hour (IBW) 2, 4
• Postoperative rate: 1.33 mg/kg/hour if continued in recovery or ICU 4
• The French guidelines suggest a range of 1-2 mg/kg/hour, but adhering to 1.5 mg/kg/hour provides adequate benefit with lower toxicity risk 1
• Absolute maximum: 120 mg/hour regardless of patient weight 2

Duration Limits

• Maximum continuous infusion: 24 hours 2
• If continuation beyond 24 hours is absolutely necessary, reduce infusion rate by 50% because lidocaine's half-life increases from ~100 minutes to 3.22 hours with prolonged administration 2
• Discontinue 30 minutes before end of surgery or before discharge from recovery area 4

Clinical Indications and Evidence

Surgical Types with Proven Benefit

• Abdominal surgery (laparoscopic and open): Strongest evidence for pain reduction, opioid sparing, and improved bowel recovery 1, 5, 6
• Pelvic surgery: Recommended by French expert panel with similar benefits 1
• Spinal surgery: Included in guideline recommendations 1
• Renal surgery: Demonstrated 31% reduction in isoflurane requirement and 27% reduction in remifentanil consumption 7

Outcomes Improved by IV Lidocaine

• Pain reduction at 1-4 hours postoperatively (mean difference -0.84 cm on VAS) and at 24 hours (-0.34 cm), though not sustained at 48 hours 5
• Opioid requirement reduced by approximately 8.44 mg morphine equivalents in 24 hours 6
• Time to first flatus reduced by 7.62 hours 6
• Time to first bowel movement reduced by 10.71 hours 6
• Postoperative nausea and vomiting reduced by 29% (RR 0.71) 6
• Hospital length of stay reduced by approximately 4 hours 6

Surgeries Where Benefit Is NOT Established

• Breast surgery: A 2012 study found no significant benefit for bowel function, pain intensity, analgesic consumption, or hospital stay after breast plastic surgery, despite reducing sevoflurane consumption by 5% 8
• Peripheral surgeries generally lack evidence of meaningful clinical benefit 8

Safety Requirements and Monitoring

Absolute Contraindications

• Body weight <40 kg: Do not use IV lidocaine 3, 2
• Known allergy to amide-type local anesthetics 3
• Advanced liver failure: Severely impaired clearance leads to toxic accumulation 3
• Third-degree heart block (per question context)
• Active seizure disorder (per question context)

Relative Contraindications (Use with Extreme Caution)

• Pre-existing cardiac disease or electrolyte disturbances 3, 2
• History of seizures or seizure disorders 3, 2
• Renal impairment 3, 2
• Moderate hepatic insufficiency 3, 2
• Pregnancy or lactation 2
• Age >70 years (increased toxicity risk) 3

Mandatory Monitoring During Administration

• During loading dose: Continuous ECG, pulse oximetry, and blood pressure every 5 minutes throughout infusion and for 15 minutes afterward 2
• Anesthesiologist presence required during entire loading phase 2
• Postoperative monitoring: If continued outside OR, patient must be in intermediate-care unit with vital signs every 15 minutes for first hour, then hourly 2

Equipment and Administration Requirements

• Dedicated infusion pump with locked upper-rate limit 2
• Separate IV line with 0.9% saline flush at 10 mL/hour to maintain patency 2
• One-way valve in line to prevent retrograde flow 2
• 20% lipid emulsion immediately available for treatment of local anesthetic systemic toxicity (LAST) 3, 2
• Resuscitation equipment must be present 3

Critical Safety Intervals with Other Local Anesthetics

Avoiding Cumulative Toxicity

• Remove all topical 5% lidocaine patches before starting IV infusion 3, 9
• Do not start IV lidocaine within 4 hours of any peripheral nerve block, fascial plane block, or local infiltration 3, 2
• Do not perform nerve blocks until 4 hours after stopping IV lidocaine infusion 2
• Wait 4 hours before administering bolus doses through wound catheters or epidural catheters after stopping IV lidocaine 2
• Continuous wound catheter or epidural infusions may begin 30 minutes after IV lidocaine is discontinued 2

Recognition of Lidocaine Toxicity

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

• Perioral numbness and facial tingling 3, 2
• Tongue and lip tingling 3, 2
• Tinnitus (ringing in ears)—often the earliest sign 3
• Metallic taste 2
• Light-headedness and dizziness 3, 2
• Slurred speech 3, 2
• Visual disturbances 2

Severe Toxicity (Plasma >10 μg/mL)

• Muscle twitching and tremor 3
• Confusion and altered mental status 3
• Loss of consciousness 3, 2
• Seizures and convulsions 3, 2
• Respiratory arrest 3, 2
• Cardiac arrhythmias 3, 2
• Myocardial depression and cardiovascular collapse 3, 2

Immediate Management

• Discontinue lidocaine immediately if any signs of toxicity appear 3
• Administer 20% lipid emulsion according to LAST protocol 3, 2
• Initiate full resuscitation as needed 3

Factors Increasing Toxicity Risk

Patient-Specific Risk Factors

• Acidemia: Increases free drug by enhancing dissociation from plasma proteins 2
• Hypoalbuminemia: Increases free plasma drug concentration 2
• Low skeletal muscle mass: Reduces drug reservoir capacity 2
• Obesity: Using actual body weight instead of IBW leads to inadvertent overdosing 2

Drug Interactions

• Beta-blockers: Reduce lidocaine metabolism 2
• Amiodarone: Decreases clearance, particularly problematic with prolonged infusions 2
• Cytochrome P450 inhibitors and inducers: Affect metabolism 2

Mechanism of Benefit

Intravenous lidocaine provides analgesia through multiple mechanisms beyond sodium channel blockade 1, 4:

• Anti-inflammatory properties: Inhibits priming of neutrophilic granulocytes, reducing superoxide anion liberation 4
• Anti-hyperalgesic effects: Modulates central pain processing 1
• Analgesic properties: Direct pain reduction independent of opioid pathways 1

Institutional Implementation

Governance Requirements

• Hospital medication governance committee approval required before implementing protocols 2
• Informed consent should be obtained when feasible, explaining off-label use 2
• Standardized commercially prepared lidocaine concentration throughout institution 2