Identifying a Potential Nerve Injury After Nerve Block

Identifying a potential nerve injury following a peripheral nerve block is critical to ensuring prompt treatment and mitigating long-term complications. Although peripheral nerve blocks are considered safe, the risk of iatrogenic nerve injury—though rare—is clinically significant and warrants careful monitoring and diagnostic vigilance. Post-block nerve injury may arise from several mechanisms, including direct needle trauma, local anesthetic neurotoxicity, compression due to hematoma or edema, or ischemic insult. Early identification hinges on a systematic approach involving preoperative risk stratification, intraoperative vigilance, and postoperative neurological assessment.

A hallmark early sign of potential nerve injury during administration of the block is the elicitation of sharp, electric-like pain or paresthesia upon injection. Liguori observed that these symptoms, particularly during brachial plexus blocks, may indicate intraneural injection and should prompt immediate cessation of anesthetic administration to reduce the risk of long-term damage (1). Despite advances in techniques like ultrasound guidance, some evidence shows that these methods have not significantly reduced the overall incidence of block-related peripheral nerve injuries (PNIs). Brull et al. emphasized that nerve injury may still occur due to factors beyond visualization, such as ischemia or inflammatory responses, making postprocedural assessment essential (2).

Symptoms of nerve injury can manifest immediately or up to a few days after surgery. Persistent motor weakness, sensory deficits, or dysesthesia that extend beyond 48 hours after the block should raise concern. Hewson et al. noted that transient neurological symptoms are not uncommon; however, persistence of symptoms beyond one week requires a formal electrodiagnostic evaluation to distinguish between neuropraxia and more severe axonotmesis or neurotmesis (3). Electrodiagnostic studies, such as nerve conduction studies and electromyography, typically provide the most definitive means of evaluating the extent and nature of the injury. However, clinicians should wait at least two to three weeks post-injury for optimal diagnostic sensitivity because Wallerian degeneration must occur first.

The differential diagnosis must also consider surgical etiology, especially for surgeries involving the limbs. Droog et al. found that, of the 14 patients with documented nerve injuries after upper extremity surgery, 11 likely resulted from surgery rather than anesthesia, highlighting the importance of interdisciplinary communication and comprehensive perioperative documentation (4). Furthermore, preexisting conditions such as diabetes mellitus or anatomical variations can increase patients’ susceptibility to nerve injury and must be considered during the preoperative evaluation.

Preventive strategies are the cornerstone of reducing nerve injuries. These strategies include using the lowest effective volume of local anesthetic, carefully positioning the patient, frequently aspirating to avoid intravascular injection, and using real-time ultrasound to ensure extraneural placement. Brull et al. and others recommend keeping patients awake or lightly sedated during block placement so they can report warning symptoms. This approach enhances safety by providing sensory feedback (5). Furthermore, if signs and symptoms indicate potential nerve injury due to the block, early referral to neurology or pain specialists can help guide management and prevent chronic neuropathic sequelae.

Ultimately, identifying potential nerve injury following a nerve block depends on clinical vigilance and interdisciplinary collaboration. Continued efforts in education, improved technique, and systematic postoperative follow-up will help ensure that the benefits of regional anesthesia are realized with minimal complications.

References

1. Liguori GA. Complications of regional anesthesia: nerve injury and peripheral neural blockade. J Neurosurg Anesthesiol. 2004;16(1):84-86. doi:10.1097/00008506-200401000-00018
2. Brull R, Hadzic A, Reina MA, Barrington MJ. Pathophysiology and Etiology of Nerve Injury Following Peripheral Nerve Blockade [published correction appears in Reg Anesth Pain Med. 2024 May 7;49(5):e2. doi: 10.1136/AAP.0000000000000125corr1.]. Reg Anesth Pain Med. 2015;40(5):479-490. doi:10.1097/AAP.0000000000000125
3. Hewson DW, Bedforth NM, Hardman JG. Peripheral nerve injury arising in anaesthesia practice. Anaesthesia. 2018;73 Suppl 1:51-60. doi:10.1111/anae.14140
4. Droog W, Lin DY, van Wijk JJ, et al. Is It the Surgery or the Block? Incidence, Risk Factors, and Outcome of Nerve Injury following Upper Extremity Surgery. Plast Reconstr Surg Glob Open. 2019;7(9):e2458. Published 2019 Sep 25. doi:10.1097/GOX.0000000000002458
5. Chui J, Murkin JM, Posner KL, Domino KB. Perioperative Peripheral Nerve Injury After General Anesthesia: A Qualitative Systematic Review. Anesth Analg. 2018;127(1):134-143. doi:10.1213/ANE.0000000000003420