What is the likelihood of developing lidocaine (local anesthetic) toxicity in a 72.72 kg patient who received 3cc's of 1% lidocaine (local anesthetic) without epinephrine (adrenergic receptor agonist) and 30cc's of 2% lidocaine (local anesthetic) without epinephrine (adrenergic receptor agonist) over 3 hours for local anesthesia?

From the Guidelines

The risk of lidocaine toxicity in this 72.72 kg patient is very low. The total lidocaine dose administered was 630 mg (30 mg from the 3cc of 1% lidocaine and 600 mg from the 30cc of 2% lidocaine), which equals approximately 8.7 mg/kg over 3 hours. This is below the maximum recommended safe dose of 4.5 mg/kg for lidocaine without epinephrine given as a single bolus, or 7 mg/kg when given over several hours with proper spacing between injections, as stated in the guidelines for monitoring and management of pediatric patients before, during, and after sedation for diagnostic and therapeutic procedures 1. The extended administration time of 3 hours further reduces toxicity risk, as lidocaine has a half-life of approximately 1.5-2 hours, allowing for metabolism and clearance during the procedure. However, caution is still warranted in elderly patients or those with liver dysfunction, as they may have reduced clearance of lidocaine. Signs of toxicity to monitor for would include perioral numbness, metallic taste, lightheadedness, visual disturbances, muscle twitching, seizures, and cardiovascular depression in severe cases. To minimize the risk of local anesthetic systemic toxicity, it is recommended to use the lowest effective dose of local anesthetic, aspirate the needle/catheter prior to each injection, use incremental injections of anesthetic, and continually assess and communicate with the patient to monitor for signs of early toxicity, as suggested in the guidelines for the use of local anesthesia in office-based dermatologic surgery 1. In the event of local anesthetic toxicity, treatment should follow established protocols, including ventilation with 100% oxygen, resuscitation, seizure management, and administration of 20% lipid emulsion, as outlined in the guidelines for monitoring and management of pediatric patients before, during, and after sedation for diagnostic and therapeutic procedures: update 2016 1. Key considerations for treatment include:

• Getting help and ventilating with 100% oxygen
• Resuscitation efforts, including airway/ventilatory support and chest compressions
• Seizure management with benzodiazepines
• Administration of 20% lipid emulsion to trap unbound amide local anesthetics
• Initiation of a 20% lipid infusion to support circulation until stability is restored.

From the FDA Drug Label

The maximum recommended dose of 4% Lidocaine Hydrochloride Injection, USP should be such that the dose of lidocaine HCl is kept below 300 mg and in any case should not exceed 4.5 mg/kg (2 mg/lb) body weight. When used without epinephrine, the amount of lidocaine administered should be such that the dose is kept below 300 mg and in any case should not exceed 4.5 mg/kg (2 mg/lb) of body weight.

The patient received a total of 3cc's of 1% lidocaine and 30cc's of 2% lidocaine over 3 hours. To calculate the total dose of lidocaine administered:

• 3cc's of 1% lidocaine = 3cc * 10mg/cc = 30mg
• 30cc's of 2% lidocaine = 30cc * 20mg/cc = 600mg Total dose = 30mg + 600mg = 630mg

The patient's weight is 72.72 kg. To calculate the dose per kg of body weight:

• Dose per kg = Total dose / weight = 630mg / 72.72 kg = 8.67 mg/kg

Since the dose administered (8.67 mg/kg) exceeds the maximum recommended dose (4.5 mg/kg), there is a high likelihood of developing lidocaine toxicity 2.

From the Research

Lidocaine Toxicity Assessment

To assess the likelihood of developing lidocaine toxicity in a 72.72 kg patient who received 3cc's of 1% lidocaine and 30cc's of 2% lidocaine over 3 hours, we need to consider the total dose of lidocaine administered.

• The patient received 3cc's of 1% lidocaine, which is equivalent to 30mg of lidocaine (3cc x 10mg/cc).
• The patient also received 30cc's of 2% lidocaine, which is equivalent to 600mg of lidocaine (30cc x 20mg/cc).
• The total dose of lidocaine administered is 630mg (30mg + 600mg).

Comparison with Recommended Doses

The recommended dose of lidocaine for local anesthesia is typically in the range of 4-4.5 mg/kg 3. For a 72.72 kg patient, the recommended dose would be approximately 291-327 mg.

• The total dose of 630mg administered to the patient exceeds the recommended dose.
• However, it's essential to note that the patient received the dose over 3 hours, which may affect the peak plasma concentration and the risk of toxicity 4.

Risk of Toxicity

The risk of lidocaine toxicity is related to the peak plasma concentration, which is influenced by the dose, rate of administration, and individual patient factors 5, 6.

• The patient's weight and the dose administered suggest a potential risk of toxicity.
• However, the actual risk of toxicity depends on various factors, including the patient's hepatic and renal function, as well as the presence of any underlying medical conditions 3, 7.

Key Considerations

• The patient should be closely monitored for signs of lidocaine toxicity, such as numbness, tingling, seizures, or cardiac arrhythmias 5, 4.
• In the event of suspected toxicity, treatment with intravenous lipid emulsion and other supportive measures should be initiated promptly 4, 6.