Local Anesthetic Systemic Toxicity

May 20, 2024

Local anesthetics play a crucial role in modern medicine, providing pain relief during various medical procedures. However, like any medication, they carry potential risks. One of the most serious risks is local anesthetic systemic toxicity. Local anesthetic systemic toxicity occurs when local anesthetic agents inadvertently enter the systemic circulation, leading to harmful effects on and toxicity for organ systems. Today in the U.S., major local anesthetic systemic toxicity events are documented in 0.04 to 1.8 of 1000 peripheral nerve blocks 1.

Local anesthetics work by blocking nerve impulses in a specific area of the body, thereby numbing the sensation of pain, and are commonly administered in surgical settings. While local anesthetics are generally safe when administered correctly, systemic toxicity can occur due to factors such as inadvertent intravascular injection, excessive dosage, rapid absorption, or impaired metabolism of the drug. In particular, if a large amount of local anesthetic reaches the systemic circulation, supratherapeutic blood and tissue levels can cause toxicity 2.

Symptoms can vary depending on the severity of toxicity and the type of local anesthetic involved. Early signs may include CNS (central nervous system) excitatory effects such as restlessness, anxiety, tremors, and confusion. As toxicity progresses, patients may experience CNS depression manifested through drowsiness, loss of consciousness, seizures, and respiratory depression. Cardiovascular manifestations, including arrhythmias, hypotension, and cardiac arrest, can also occur, posing life-threatening risks to the patient 3.

Prompt recognition and management of local anesthetic systemic toxicity is critical for preventing adverse outcomes. Healthcare providers should maintain a high index of suspicion, especially during procedures involving large doses or continuous infusion of local anesthetics. When toxicity occurs, immediate interventions should be initiated, including stopping the administration of the local anesthetic, ensuring adequate oxygenation and ventilation, and initiating advanced cardiac life support (ACLS) protocols if necessary 4.

Treatment strategies for local anesthetic systemic toxicity aim to mitigate systemic toxicity and support vital functions. Lipid emulsion therapy is critical in the management of local anesthetic systemic toxicity. Lipid emulsions sequester lipophilic drugs such as local anesthetics and reducing their concentration in the systemic circulation. Intralipid, a commonly used lipid emulsion, is administered intravenously as a bolus followed by a continuous infusion according to established protocols 3,4.

In addition to lipid emulsion therapy, supportive measures such as airway management, hemodynamic support, and anti-arrhythmic medications may be necessary based on the patient’s clinical presentation. Close monitoring of vital signs, electrocardiography, and neurological status is essential to guide ongoing management and assess the response to treatment 3,4.

Prevention remains the cornerstone of reducing the risk of local anesthetic systemic toxicity. Healthcare providers should adhere to established guidelines for the safe administration of local anesthetics, including proper dosage calculation, aspiration before injection to confirm intravascular placement, and utilization of ultrasound guidance for nerve blocks to enhance accuracy and safety 4,5.

Although rare, local anesthetic systemic toxicity is a potentially life-threatening complication of local anesthetic administration. Healthcare professionals must be vigilant in recognizing its signs and symptoms and be prepared to initiate prompt and effective management strategies.


1.        Local anesthetic systemic toxicity – UpToDate. Available at: https://www.uptodate.com/contents/local-anesthetic-systemic-toxicity. (Accessed: 28th April 2024)

2.        Local Anesthetic Systemic Toxicity – NYSORA. Available at: https://www.nysora.com/topics/complications/local-anesthetic-systemic-toxicity/. (Accessed: 28th April 2024)

3.          Local anesthetic systemic toxicity (local anesthetic systemic toxicity) – NYSORA. Available at: https://www.nysora.com/anesthesia/local-anesthetic-systemic-toxicity-last/. (Accessed: 28th April 2024)

4.        Local Anesthetic Toxicity – StatPearls – NCBI Bookshelf. Available at: https://www.ncbi.nlm.nih.gov/books/NBK499964/. (Accessed: 28th April 2024)

5.        El-Boghdadly, K., Pawa, A. & Chin, K. J. Local anesthetic systemic toxicity: current perspectives. Local Reg. Anesth. 11, 35 (2018). doi: 10.2147/LRA.S154512