Nerve Injury After a Nerve Block
Peripheral nerve blocks are a routine part of anesthesia for shoulder, knee, hip, hand, foot, and many other operations. When a patient wakes up with numbness, weakness, or burning pain that does not go away, the block is often the first thing blamed. Sometimes the block is the cause. Often something else is, or several things are.
Two questions matter. Was the block indicated and performed within accepted practice? And was the injury caused by the block, or by the surgery, positioning, a tourniquet, or a condition the patient already had? This article explains how a physician works through those questions, and which records usually answer them.
How often do nerve blocks cause lasting nerve injury?
The published literature makes a clear distinction between temporary symptoms and permanent injury.
- A review of 32 studies by Brull and colleagues (Anesthesia & Analgesia, 2007) estimated neuropathy rates of about 2.84 per 100 after interscalene blocks, 1.48 per 100 after axillary blocks, and 0.34 per 100 after femoral blocks. The authors concluded that permanent neurologic injury after regional anesthesia is rare. Among 16 studies of peripheral nerve blocks, only one permanent neuropathy was reported.
- A prospective audit of more than 7,000 peripheral nerve and plexus blocks by Barrington and colleagues (Regional Anesthesia and Pain Medicine, 2009) found block-related nerve injury in 0.4 per 1,000 blocks. The authors concluded that new neurologic symptoms after surgery were most likely unrelated to the block.
- A registry of 12,668 ultrasound-guided blocks by Sites and colleagues (Regional Anesthesia and Pain Medicine, 2012) reported neurologic symptoms lasting longer than 5 days in 1.8 per 1,000 blocks, and longer than 6 months in 0.9 per 1,000.
Two practical points follow. First, short-lived symptoms after a block are fairly common, while lasting injury caused by the block is uncommon. Second, the fact that a complication is rare does not settle either question in a given case. A rare complication can happen with flawless technique. A common and harmless symptom can also hide a real injury that nobody followed up.
What standard-of-care review looks at
The American Society of Regional Anesthesia and Pain Medicine (ASRA) has published practice advisories on neurologic complications, including The Second ASRA Practice Advisory on Neurologic Complications Associated With Regional Anesthesia and Pain Medicine (Neal and colleagues, 2015). That advisory addresses, among other topics, the role of ultrasound guidance and injection pressure monitoring, blocks given to patients who are anesthetized or deeply sedated, patients with pre-existing neurologic disease, and the nerve injury risk that comes with common orthopedic operations. It also includes a diagnostic and treatment algorithm for new deficits. It is a practice advisory, not a rulebook, and an expert should describe it that way.
A careful standard-of-care review usually asks:
- Indication and choice of block. Was a block reasonable for this operation and this patient? Were patient risk factors, such as diabetes or an existing neuropathy, identified and weighed?
- Informed consent. Was nerve injury discussed as a risk, along with the alternatives?
- Patient state during placement. Was the patient awake, lightly sedated, or under general anesthesia? Could the patient report pain or paresthesia during the injection?
- Technique. Was ultrasound used, a nerve stimulator, or both? How were needle position, injection, and any reported pain or paresthesia handled? No technique removes the risk entirely. Every block in the Sites registry was ultrasound-guided, and neurologic symptoms still occurred.
- Drug, dose, and adjuvants. Were the local anesthetic and any additives appropriate in kind and amount?
- Documentation. Is there a block note, a time-out, and, where available, saved ultrasound images?
- Follow-up. When a deficit appeared, was it examined, documented, and referred in reasonable time?
The same questions apply whether the block was performed by an attending anesthesiologist, a trainee, or a nurse anesthetist (CRNA).
Causation: the block is one of several possible causes
Postoperative nerve injury often has more than one possible cause. When an expert evaluates causation, the usual candidates include:
- direct or traction injury during the operation itself;
- positioning and pressure during a long procedure;
- tourniquet pressure and duration;
- tight casts, splints, or dressings, or swelling and hematoma after surgery; and
- a neuropathy the patient already had, whether diagnosed or not.
Several features help separate these causes. Anatomic distribution asks whether the deficit maps to the nerve that was blocked, to the surgical field, or to a pressure point. Timing asks whether symptoms were present right away, appeared after the block wore off, or developed later. Electrodiagnostic studies (EMG and nerve conduction studies), and when they were done, can help locate a lesion and estimate how old it is. Pre-existing findings in earlier records can show a condition that came before the procedure. A careful evaluation weighs the surgical and patient-related causes, not only the block.
Records that usually matter
- Preoperative history and physical, including any documented neurologic exam
- Consent forms for anesthesia and for the block
- The anesthesia record and the block procedure note, with saved ultrasound images if any
- The operative note, including positioning and tourniquet times
- PACU, nursing, and physical therapy notes documenting sensation and strength
- Follow-up notes, neurology consults, EMG and nerve conduction reports, and imaging
- Prior records showing earlier neurologic symptoms or diagnoses
The published background behind this review
Dr. Urits co-authored Upper extremity regional anesthesia techniques: A comprehensive review for clinical anesthesiologists (Jones and colleagues, 2020). It covers the anatomy, techniques, and potential complications of the brachial plexus blocks and other upper extremity blocks. He was also first author of Truncal regional nerve blocks in clinical anesthesia practice (2019), which covers the techniques, indications, and complications of chest wall, abdominal, and paraspinal blocks. His opinions rest on the complete record, the peer-reviewed literature, and generally accepted methodology.
Key takeaways
- Short-lived symptoms after a block are fairly common. Lasting injury caused by the block is uncommon, but it does happen.
- Standard of care turns on indication, consent, technique, documentation, and follow-up, not on the outcome alone.
- Causation calls for a structured look at surgical, positioning, tourniquet, and patient factors, as well as the block itself.
- The block note, ultrasound images, operative note, and electrodiagnostic studies often show what happened.
References
- Brull R, McCartney CJ, Chan VW, El-Beheiry H. Neurological complications after regional anesthesia: contemporary estimates of risk. Anesth Analg. 2007;104(4):965-974. Abstract: https://pubmed.ncbi.nlm.nih.gov/17377115/
- Barrington MJ, Watts SA, Gledhill SR, et al. Preliminary results of the Australasian Regional Anaesthesia Collaboration: a prospective audit of more than 7000 peripheral nerve and plexus blocks for neurologic and other complications. Reg Anesth Pain Med. 2009;34(6):534-541. Abstract: https://pubmed.ncbi.nlm.nih.gov/19916206/
- Sites BD, Taenzer AH, Herrick MD, et al. Incidence of local anesthetic systemic toxicity and postoperative neurologic symptoms associated with 12,668 ultrasound-guided nerve blocks: an analysis from a prospective clinical registry. Reg Anesth Pain Med. 2012;37(5):478-482. Abstract: https://pubmed.ncbi.nlm.nih.gov/22705953/
- Neal JM, Barrington MJ, Brull R, et al. The Second ASRA Practice Advisory on Neurologic Complications Associated With Regional Anesthesia and Pain Medicine: Executive Summary 2015. Reg Anesth Pain Med. 2015;40(5):401-430. Abstract: https://pubmed.ncbi.nlm.nih.gov/26288034/
- Jones MR, Novitch MB, Sen S, ..., Urits I, Cornett EM, Kaye AD. Upper extremity regional anesthesia techniques: A comprehensive review for clinical anesthesiologists. Best Pract Res Clin Anaesthesiol. 2020;34(1):e13-e29. Abstract: https://pubmed.ncbi.nlm.nih.gov/32334792/
- Urits I, Ostling PS, Novitch MB, et al. Truncal regional nerve blocks in clinical anesthesia practice. Best Pract Res Clin Anaesthesiol. 2019;33(4):559-571. Abstract: https://pubmed.ncbi.nlm.nih.gov/31791571/
Related: Regional Anesthesia and Nerve Block Cases
Educational information only. Not legal or medical advice.
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