Nerve blocks are performed by injecting local anesthetic in a specific area around a target nerve to provide regional pain relief for surgery or medical conditions. Although they provide many benefits and are safe procedures, a small chance for complications exists. Accidental intravascular injection of local anesthetic during a nerve block is a significant medical challenge with potentially serious consequences.
Local anesthetics, such as lidocaine, bupivacaine, and ropivacaine, block sodium channels necessary for nerve signaling, thereby providing effective local or regional anesthesia (1). The type of anesthetic selected for a nerve block typically depends on the required duration and depth of anesthesia, with agents such as bupivacaine preferred for longer procedures due to their potent and prolonged anesthetic properties. However, the high potency of bupivacaine also increases the risk of severe cardiotoxic effects if it accidentally enters the bloodstream (1).
Although incidents of accidental intravascular injection when attempting a nerve block are rare, their occurrence can lead to critical complications. The risk is compounded by factors such as complex anatomy at the injection site and the specific techniques used by healthcare providers. For example, areas such as the cervical paravertebral space and the axillary region are anatomically complex and highly vascularized, making them more prone to inadvertent intravascular injection (2). The likelihood of such events is increased by improper needle placement or inadequate aspiration before injection, particularly in settings where visibility or access to the injection site is limited.
The spectrum of complications caused by accidental intravascular injection of local anesthetic is broad, ranging from mild symptoms such as transient sensory disturbances—like metallic taste or ringing in the ears—to severe, life-threatening conditions such as seizures, profound hypotension, and dangerous arrhythmias. In severe cases, these symptoms can escalate to cardiovascular collapse, requiring urgent and effective intervention. The severity and specific manifestations of these complications are generally related to the amount of anesthetic inadvertently injected and how rapidly it is absorbed into circulation (3). Management of such events is critical and includes several immediate measures: discontinuation of further anesthetic administration, ensuring adequate ventilation and circulation, and administration of intravenous lipid emulsions. The latter treatment is particularly effective as it forms a lipid “sink” that isolates the lipophilic anesthetic molecules, significantly reducing their availability to affect the heart and brain, thus reducing the risk of severe systemic toxicity (4).
Several proactive measures are recommended to prevent accidental intravascular injection of local anesthetic during a nerve block. The use of ultrasound guidance during needle placement can dramatically reduce the risk of accidental vascular puncture by providing real-time visualization of the needle’s path relative to surrounding structures. Syringe aspiration prior to injection is also critical; this simple step can reveal whether the needle tip is in a blood vessel, as indicated by the presence of blood in the syringe. In addition, using the lowest effective dose of anesthetic minimizes potential toxicity should an intravascular injection occur. The ongoing education of healthcare professionals on the pharmacokinetic and toxicologic aspects of local anesthetics is essential. Regular training and simulation exercises can improve injection technique and emergency response skills, further reducing the likelihood of adverse events (4).
Although nerve blocks are indispensable tools for pain management in many areas of medicine, their administration is not without risk. A thorough understanding of the pharmacodynamics involved, a vigilant recognition of the associated risks, and the adoption of rigorous preventive measures are critical to ensuring the safe use of these techniques. By integrating advanced techniques, comprehensive training, and immediate management protocols, healthcare providers can significantly improve patient safety and minimize the risks associated with inadvertent intravascular injection of local anesthetics.
References
- Garcia-Blanco M, Scanlan S. Accidental Intravascular Local Anesthetic Injection of the Facial Artery. Anesth Prog. 2021;68(1):29-32. doi:10.2344/anpr-67-03-03
- Epstein E. Accidental intravascular injection during infiltration anesthesia of the skin. Cutis. 1991;47(6):394-396.
- Yuan YP, Chen HF, Yang C, Tian FB, Huang SQ. A case of accidental intrathecal injection of a large dose of ropivacaine during cesarean section. Int J Clin Exp Med. 2014;7(8):2383-2385. Published 2014 Aug 15.
- Mather LE, Copeland SE, Ladd LA. Acute toxicity of local anesthetics: underlying pharmacokinetic and pharmacodynamic concepts. Reg Anesth Pain Med. 2005;30(6):553-566. doi:10.1016/j.rapm.2005.07.186