Regional nerve block is a technique in anesthesia that can provide long-lasting analgesia [1]. Although minor complications may occur, major complications remain rare. The recent emergent use of ultrasound has only further decreased the risk associated with this procedure [2]. In regional blocks, local anesthetic is injected in the area around a target nerve to temporarily block all sensation that the nerve carries. However, regional block can also affect motor function, and the process of motor recovery is an important consideration for patients and their clinical teams.

A number of factors affect the successful implementation of a regional block, which thereafter impacts motor recovery. One study sought to assess the effect of various volumes injected on the duration and overall success of sciatic nerve block for surgical analgesia, with a successful block defined as a complete sensory and motor block at 60 minutes. The minimum time to complete block, threshold current, duration of sensory and motor block, postoperative pain, and analgesic requirements were recorded. Data analyses revealed that injecting 10 mL of 0.5% bupivacaine or ropivacaine yielded a comparable duration and onset of sensory and motor blockade as volumes as large as 30 mL. This suggests that moderate doses can provide a successful regional nerve block without the risks associated with large doses, such as impaired motor recovery.

The choice of anesthetic also has an important impact on the trajectory of a patient’s motor recovery after a regional block. While bupivacaine, at its usual dose, is the most common local anesthetic used in clinical practice, it may result in motor weakness which can delay patient discharge. Therefore, a group of researchers sought to evaluate the effect of adding fentanyl as an adjuvant to this local anesthetic in order to assess the feasibility of reducing the usual dose administered. Data revealed that, although the onset of motor blockade was comparable in both the groups, motor functions returned and patients were able to ambulate significantly faster when receiving a bupivacaine/fentanyl combination than when receiving bupivacaine alone [3]. The anesthetics used in a regional block is thus critical to swift motor recovery in patients.

One published report documented the case of a prolonged supraclavicular brachial plexus block which required, without a perceivable cause, nearly four months to recover from. In this case, a 22-year-old man posted for open reduction and internal fixation of both forearm bones was administered an ultrasound-guided supraclavicular brachial plexus block. While the intraoperative period was uneventful, the block persisted for a long time, for which all perceivable causes were ruled out. In the end, a period of 19 weeks was required for the entire block to regress with no residual neurological deficits [4]. In addition, there are a number of published reports of prolonged blockade without measurable errors in block administration. Complete recovery in such cases has been reported to vary between 40 and 84 hours following the block [5,6]. However, no clear pattern has yet been identified in order to minimize such occurrences.

Such cases remain anecdotal and overall, regional nerve block is followed by successful motor recovery. Understanding the factors involved in motor recovery will continue to be key to ensuring the smoothest recovery periods possible for patients into the future across clinical contexts.

References

1. Faiz, S. H.-R. & Mohseni, M. The Potential Role of Regional Anesthesia in Perioperative Anti-Inflammatory Treatments. Anesthesiol. Pain Med. (2012). doi:10.5812/aapm.5067

2. Davis, J. J., Swenson, J. D., Greis, P. E., Burks, R. T. & Tashjian, R. Z. Interscalene

block for postoperative analgesia using only ultrasound guidance: the outcome in 200 patients. J. Clin. Anesth. (2009). doi:10.1016/j.jclinane.2008.08.022

3. Singh, A., Habib, S. K. & Haleem, S. An Assessment of Motor Recovery Following Spinal Anaesthesia with Bupivacaine and Bupivacaine Fentanyl Combination: A Randomized Controlled Trial. Ann. Int. Med. Dent. Res. (2020).

4. Shrestha, N. et al. Delayed Neurological Recovery After Ultrasound-Guided Brachial Plexus Block: A Case Report. Local Reg. Anesth. 13, 33 (2020). doi: 10.2147/LRA.S250989

5. Brockway, M. S., Winter, A. W. & Wildsmith, J. A. W. Prolonged brachial plexus block with 0.42% bupivacaine. Br. J. Anaesth. (1989). doi:10.1093/bja/63.5.604

6. Lehavi, A., Shenderey, B. & Katz, Y. S. Prolonged nerve blockade in a patient treated with lithium. Local Reg. Anesth. (2012). doi:10.2147/lra.s29593