What is the risk of lidocaine toxicity in a 72.72 Kg patient who received 3cc's of 1% lidocaine (lidocaine) with epinephrine (epinephrine) and 30cc's of 2% lidocaine (lidocaine) without epinephrine (epinephrine) for local anesthesia?

From the Guidelines

The risk of lidocaine toxicity in this 72.72 kg patient is low as the total dose administered is within safe limits. The patient received 3 cc of 1% lidocaine with epinephrine (30 mg lidocaine) plus 30 cc of 2% lidocaine without epinephrine (600 mg lidocaine), for a total dose of 630 mg. For a 72.72 kg patient, this equals approximately 8.7 mg/kg, which is below the maximum recommended dose of 7 mg/kg for lidocaine without epinephrine and 14 mg/kg for lidocaine with epinephrine, as stated in the guidelines for monitoring and management of pediatric patients before, during, and after sedation for diagnostic and therapeutic procedures 1. The presence of epinephrine in part of the dose helps reduce systemic absorption of lidocaine by causing local vasoconstriction, further enhancing safety. However, clinicians should still monitor for early signs of toxicity including perioral numbness, metallic taste, lightheadedness, tinnitus, and visual disturbances. More severe toxicity can manifest as seizures, cardiac arrhythmias, or cardiovascular collapse. Elderly patients and those with liver disease, heart failure, or on certain medications may be more susceptible to toxicity even at lower doses, so careful assessment of the patient's overall condition remains important despite the calculated dose being within acceptable limits. It's also worth noting that the guidelines for the early management of patients with acute myocardial infarction provide information on the dosage and administration of lidocaine, but the context of the question is related to local anesthesia, which is more closely related to the guidelines provided in 1. Therefore, the recommendation is based on the most recent and relevant guidelines for local anesthesia. Some key points to consider when administering local anesthetic agents include:

• Calculating the maximum allowable safe dosage (eg, mg/kg) before administration
• Using lower doses when injecting into vascular tissues
• Aspirating frequently to minimize the likelihood that the needle is in a blood vessel
• Monitoring for early signs of toxicity
• Being aware of the potential for enhanced sedative effects when local anesthetic drugs are used in combination with other sedatives or opioids. Overall, the risk of lidocaine toxicity in this patient is considered low, but careful monitoring and assessment are still necessary to ensure patient safety.

From the FDA Drug Label

The lowest dosage that results in effective anesthesia should be used to avoid high plasma levels and serious adverse effects. Repeated doses of lidocaine may cause significant increases in blood levels with each repeated dose, because of slow accumulation of the drug or its metabolites. The maximum recommended dose of ... 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.

The patient received a total of 3cc's of 1% lidocaine with epinephrine and 30cc's of 2% lidocaine without epinephrine. To calculate the total dose of lidocaine:

• 3cc's of 1% lidocaine = 3 * 10mg = 30mg
• 30cc's of 2% lidocaine = 30 * 20mg = 600mg The total dose is 30mg + 600mg = 630mg. Given the patient's weight is 72.72 Kg, the dose per kilogram is 630mg / 72.72Kg = 8.67mg/Kg. Since the dose exceeds the maximum recommended dose of 4.5 mg/kg, there is a high risk of toxicity 2 2.

From the Research

Lidocaine Toxicity Risk

The risk of lidocaine toxicity in a 72.72 Kg patient who received 3cc's of 1% lidocaine with epinephrine and 30cc's of 2% lidocaine without epinephrine for local anesthesia can be assessed based on the total dose of lidocaine administered.

• The patient received a total of 3cc's of 1% lidocaine (which is 30mg of lidocaine) and 30cc's of 2% lidocaine (which is 600mg of lidocaine).
• The total dose of lidocaine administered is 630mg.

Comparison with Recommended Dosage

• The recommended maximum dose of lidocaine for local anesthesia is 4.5mg/kg without epinephrine and 7mg/kg with epinephrine 3.
• For a 72.72 Kg patient, the maximum recommended dose without epinephrine would be 326.24mg and with epinephrine would be 508.04mg.
• The patient received a total dose of 630mg of lidocaine, which exceeds the recommended maximum dose without epinephrine but is below the maximum dose if the entire dose had epinephrine.

Risk of Toxicity

• The risk of lidocaine toxicity is higher when the recommended maximum dose is exceeded 4.
• However, the presence of epinephrine in the initial 3cc's of 1% lidocaine may reduce the risk of toxicity compared to lidocaine without epinephrine 5.
• The patient's risk of toxicity should be monitored closely, and treatment with intravenous lipid emulsion (ILE) should be considered if symptoms of systemic toxicity occur 4.

Treatment of Toxicity

• If the patient exhibits symptoms of lidocaine toxicity, such as perioral numbness, seizure-like activity, or confusion, treatment with ILE or anticonvulsant drugs like diazepam may be effective 5, 6, 7.
• The use of benzodiazepines, such as diazepam, has been shown to be effective in treating seizures induced by lidocaine toxicity 6, 7.