Neuromuscular Blockade Reversal and Re-Paralysis in Anesthesia

Neuromuscular blockade is an anesthetic technique that temporarily paralyzes skeletal muscles and is used to facilitate tracheal intubation, assist with mechanical ventilation, and to optimize surgical conditions when appropriate.¹ In most cases, the neuromuscular blocking agent is administered at the beginning of surgery and is reversed at the end. However, in certain clinical scenarios, it may be necessary for the anesthesiologist to enact neuromuscular blockade reversal during the surgery and later initiate re-paralysis to complete the surgery.

Neuromuscular blocking agents come in two categories: depolarizing and nondepolarizing. Depolarizing agents are drugs that mimic acetylcholine and bind to cholinergic receptors at the synapses of nerve cells, which causes prolonged depolarization and prevents muscle contraction. Nondepolarizing neuromuscular blockers exert the opposite effect: they block the binding of acetylcholine and thereby prevent the transmission of an action potential, leading to muscle paralysis.¹

The agent used to reverse neuromuscular blockade and muscle paralysis after surgery depends on the neuromuscular blocking agent used. Neostigmine inhibits acetylcholinesterase, the enzyme that breaks down acetylcholine, and is used for reversing nondepolarizing neuromuscular blockade.² Sugammadex is also used to reverse nondepolarizing blockade, though it works by preventing the neuromuscular blocker rocuronium from binding to the acetylcholine receptor.³ Because acetylcholinesterase would actually prolong this kind of blockade, these agents cannot be used to reverse depolarizing blockade, so depolarizing blocking agents are typically left to be metabolized and for the paralysis to wear off, though some broad-spectrum reversal agents have been reported to work for depolarizing agents.⁴

Re-paralysis, also known as recurarization, is when muscle paralysis returns after neuromuscular blockade reversal. This can occur due to several factors. For instance, an insufficient dose of sugammadex can fail to inhibit all the blocking agents, leading those that remain to move back to the acetylcholine receptor and reintroduce paralysis.⁵ Certain drugs, like magnesium sulfate, can also cause re-paralysis.⁶ Re-paralysis can lead to a number of complications, like difficulty breathing, upper airway obstruction, and low blood levels of oxygen, so anesthesiologists generally seek to prevent it.

There are, however, certain procedures and situations in which neuromuscular blockade reversal and re-paralysis are needed. Certain surgeries require monitoring of nerve function during the operation. During a thyroidectomy, for example, intraoperative monitoring of the laryngeal nerve is used to avoid injury to that nerve (a complication of this operation), which can result in permanent hoarseness and other throat and breathing issues. Monitoring the nerve’s real-time function helps to prevent any potential issues, but temporarily reversing neuromuscular blockade allows for more accurate responses when stimulating the nerve.⁷ Similarly, one study reported the repeated reversal of rocuronium using sugammadex during a discectomy—removal of a part of, or a whole, intervertebral disc of the spine—to successfully monitor spinal nerves.⁸

Additionally, neuromuscular block reversal followed by a re-paralysis can be useful when complications arise in the course of an operation. For example, in one reported case, intubation initially failed for a patient due to airway obstruction. The decision was made to reverse neuromuscular block so that they could devise a back-up plan for achieving ventilation via a different method.⁹ However, some caution that this approach should only be used in an unanticipated difficult airway due to potential complications.⁹ Ultimately, the specific approach taken by doctors and anesthesiologists should depend on the operation in question and the needs of the patient.

References

1. Cook, D. & Simons, D. J. Neuromuscular Blockade. in StatPearls (StatPearls Publishing, Treasure Island (FL), 2025).

2. Neely, G. A., Sabir, S. & Kohli, A. Neostigmine. in StatPearls (StatPearls Publishing, Treasure Island (FL), 2025).

3. Chandrasekhar, K., Togioka, B. M. & Jeffers, J. L. Sugammadex. in StatPearls (StatPearls Publishing, Treasure Island (FL), 2025).

4. Hoffmann, U. et al. Calabadion: A new agent to reverse the effects of benzylisoquinoline and steroidal neuromuscular-blocking agents. Anesthesiology 119, 317–325 (2013), DOI: 10.1097/ALN.0b013e3182910213

5. Postoperative Recurarization After Sugammadex Administration Due to the Lack of Appropriate Neuromuscular Monitoring: The Japanese Experience. Anesthesia Patient Safety Foundation https://www.apsf.org/article/postoperative-recurarization-after-sugammadex-administration-due-to-the-lack-of-appropriate-neuromuscular-monitoring-the-japanese-experience/.

6. Germano-Filho, P. A. et al. Recurarization with magnesium sulfate administered after two minutes sugammadex reversal: A randomized, double-blind, controlled trial. J. Clin. Anesth. 89, 111186 (2023), DOI: 10.1016/j.jclinane.2023.111186

7. Lu, I.-C. et al. Neuromuscular Blockade Antagonism for Thyroid Surgery During Intraoperative Neural Monitoring—An Anesthesia Perspective. Medicina (Mex.) 61, 420 (2025), https://doi.org/10.3390/medicina61030420

8. Errando, C. L., Blanco, T. & Díaz-Cambronero, Ó. Repeated sugammadex reversal of muscle relaxation during lumbar spine surgery with intraoperative neurophysiological multimodal monitoring. Rev. Esp. Anestesiol. Reanim. 63, 533–538 (2016), DOI: 10.1016/j.redar.2016.03.008

9. Paton, L., Gupta, S. & Blacoe, D. Successful use of sugammadex in a ‘can’t ventilate’ scenario. Anaesthesia 68, 861–864 (2013), DOI: 10.1111/anae.12338