What is the risk of lidocaine toxicity in a 72.72 Kg patient given 3cc 1% lidocaine with epinephrine and 30cc 2% lidocaine without epinephrine over 3 hours?

From the Guidelines

The risk of lidocaine toxicity in this 72.72 kg patient is low and within safe limits. The total lidocaine dose administered is 630 mg (30 mg from the 3cc of 1% lidocaine with epinephrine and 600 mg from the 30cc of 2% lidocaine without epinephrine), which equals approximately 8.7 mg/kg given over 3 hours. This is below the maximum recommended dose of 7 mg/kg for lidocaine without epinephrine and 14 mg/kg for lidocaine with epinephrine in a single administration, 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 the risk as lidocaine has a half-life of approximately 1.5-2 hours, allowing for metabolism during the administration period, as discussed in the study on the use of intravenous lidocaine for postoperative pain and recovery 1. However, caution is still warranted in patients who may have decreased hepatic function or cardiac issues. Monitoring for early signs of toxicity such as perioral numbness, metallic taste, lightheadedness, tinnitus, visual disturbances, or CNS excitation is recommended, as outlined in the guidelines for the early management of patients with acute myocardial infarction 1. If these symptoms appear, the lidocaine administration should be stopped immediately and supportive care provided. Additionally, the use of lipid emulsion for the treatment of local anesthetic toxicity is recommended in cases of cardiac arrest, as suggested by the consensus on science for advanced life support 1.

Some key points to consider:

• The maximum recommended dose of lidocaine without epinephrine is 7 mg/kg and with epinephrine is 14 mg/kg in a single administration.
• The half-life of lidocaine is approximately 1.5-2 hours, allowing for metabolism during the administration period.
• Monitoring for early signs of toxicity is crucial, and supportive care should be provided if symptoms appear.
• Lipid emulsion may be used for the treatment of local anesthetic toxicity in cases of cardiac arrest. It is essential to weigh the benefits and risks of lidocaine administration and to carefully monitor patients for signs of toxicity, as discussed in the study on the use of intravenous lidocaine for postoperative pain and recovery 1.

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 HCl may cause significant increases in blood levels with each repeated dose because of slow accumulation of the drug or its metabolites. Dosages should be reduced for children and for the elderly and debilitated patients and patients with cardiac and/or liver disease. Although the incidence of side effects with lidocaine HCl is quite low, caution should be exercised when employing large volumes and concentrations, since the incidence of side effects is directly proportional to the total dose of local anesthetic agent injected.

The patient received a total of 33cc of lidocaine, with 3cc of 1% lidocaine with epinephrine and 30cc of 2% lidocaine without epinephrine, over the course of 3 hours. To determine the risk of toxicity, we need to calculate the total dose of lidocaine administered:

• 3cc of 1% lidocaine = 3cc x 10mg/cc = 30mg
• 30cc of 2% lidocaine = 30cc x 20mg/cc = 600mg The total dose is 630mg of lidocaine. However, the FDA drug label does not provide a clear maximum recommended dose for a 72.72 Kg patient, and the dosages suggested are for normal healthy adults. Given the large volume and concentration of lidocaine administered, there is a risk of toxicity, but the exact chance cannot be determined from the provided information 2 2.

From the Research

Lidocaine Toxicity Risk Assessment

The risk of lidocaine toxicity in a 72.72 Kg patient given 3cc 1% lidocaine with epinephrine and 30cc 2% lidocaine without epinephrine over 3 hours can be assessed based on the available evidence.

• The initial dose of 3cc 1% lidocaine with epinephrine may increase the risk of toxicity due to the presence of epinephrine, which has been shown to potentiate the intravascular toxicity of lidocaine 3.
• The subsequent doses of 2% lidocaine without epinephrine may also contribute to the risk of toxicity, as the total dose of lidocaine administered is relatively high.
• Studies have shown that the convulsive dose of lidocaine is lower when administered with epinephrine 4, which may increase the risk of central nervous system toxicity.
• The risk of toxicity also depends on the route of administration, with intravenous administration being more toxic than intra-arterial administration 3.
• However, it is worth noting that the exact mechanism of action of lidocaine and its toxicity remains unclear, despite its known properties 5.

Factors Influencing Toxicity

Several factors can influence the risk of lidocaine toxicity, including:

• The dose and concentration of lidocaine administered
• The presence of epinephrine or other vasoconstrictors
• The route of administration
• The patient's weight and body composition
• The duration of administration

Available Evidence

The available evidence suggests that the risk of lidocaine toxicity is increased when epinephrine is present 3, 4, and that the convulsive dose of lidocaine is lower when administered with epinephrine 4. However, the exact risk of toxicity in this specific patient cannot be determined without further information.

• A study on the acute toxicity of lidocaine and prilocaine in combination with adrenaline and felypressin found that the solutions with higher concentrations of adrenaline were more toxic 6.
• A review of lidocaine toxicity reported a case of lidocaine toxicity with its typical manifestation, and emphasized the importance of recognizing and managing this potential adverse reaction 7.