The case feels routine from the start.
The patient is prepped, induction medications are administered, and intubation is smooth. The procedure commences without issue. At the end of the case, sugammadex is given, and within moments the patient opens their eyes, follows commands, and takes several strong breaths. From the perspective of the anesthesia team, everything appears exactly as it should.
Extubation is uneventful. The monitors remain stable as the patient is transported toward PACU. Then, minutes later, the situation begins to change.
The patient struggles to maintain their airway. Respirations become shallow. Oxygen saturation begins to drift downward, and what looked like a smooth recovery suddenly demands attention again.
Residual neuromuscular blockade was never supposed to be part of the story anymore. Sugammadex was supposed to fix that. Yet recurarization still occurs, even in the era of modern reversal agents. And because it follows what appears to be a successful recovery - it is uniquely easy to miss.
In the context of sugammadex, recurarization reflects the relationship between the amount of neuromuscular blocking agent present and the dose of reversal administered. Sugammadex binds free rocuronium in the plasma, allowing for rapid reversal when the dose is appropriately matched to the depth of blockade.
However, when the degree of blockade is underestimated, the administered dose may be insufficient to fully bind circulating and redistributing rocuronium. As rocuronium redistributes from peripheral compartments back into the plasma over time, it can exceed the available sugammadex, allowing neuromuscular blockade to re-emerge after an initial period of apparent recovery.1
In this context, recurarization is not incidental - it reflects incomplete reversal relative to the depth of neuromuscular blockade present.
Recurarization Still Happens - More Than We Think
Recurarization following sugammadex administration has been documented 2 , including cases in which patients initially appear to recover and are extubated without complication. As early as 2019, the Safety Committee of the Japanese Society of Anesthesiologists (JSA) released a warning highlighting the need for correct sugammadex dosing based on identified cases of postoperative recurarization, several involving respiratory compromise requiring airway support or additional reversal, with deterioration often emerging later in the postoperative period.²
Additionally, a clinical study by Kotake et al. documents up to 9.4% of patients were extubated with a train-of-four ratio < 0.9 despite reversal with sugammadex when extubation decisions were not guided by objective neuromuscular monitoring.³
Across these cases, a consistent finding was uncertainty in the degree of neuromuscular blockade at the time of reversal, often due to the absence of appropriate neuromuscular monitoring.² When recovery is incomplete, the margin for safe recovery is reduced, making subsequent weakness or recurrence of blockade more likely.
Recurarization is likely under-recognized in clinical practice, particularly when it develops after transfer of care, where events in the PACU are not always attributed to intraoperative neuromuscular management.
These events are frequently framed as dosing issues; however, accurate dosing requires knowledge of the underlying depth of neuromuscular blockade.
As emphasized in safety reviews, “the reversal dose of sugammadex should always be calculated based on the degree of neuromuscular recovery obtained with neuromuscular monitoring (ideally, objective neuromuscular monitoring).”1 Without that information, reversal dosing is based on estimation rather than measurement.
The same limitation applies when assessing neuromuscular recovery. Clinical signs alone do not reliably confirm full neuromuscular recovery, particularly at train-of-four ratios below 0.9.4
When the depth of blockade is not quantitatively measured, both reversal dosing and recovery assessment are based on estimation. In this context, recurarization is not an isolated failure; it is a foreseeable consequence of lack of objective neuromuscular assessment, with residual or recurrent blockade contributing to airway obstruction and hypoxemia in the postoperative period.
The 2023 American Society of Anesthesiologists Practice Guidelines for Monitoring and Antagonism of Neuromuscular Blockade recommend the use of quantitative neuromuscular monitoring whenever neuromuscular blocking agents are administered and advise confirming recovery to a train-of-four ratio of at least 0.9 prior to extubation.4 These recommendations are consistent with established international standards, which define adequate recovery as a train-of-four ratio ≥ 0.9 and underscore the importance of objective neuromuscular assessment.⁵
When recovery is measured, uncertainty is reduced. Recurarization, residual blockade, and postoperative respiratory complications become less likely consequences of care. It is important to remember: reversal is a treatment decision; recovery is a measurement.
Sugammadex has transformed the management of neuromuscular blockade -no doubt- but it has not eliminated the need to measure recovery.
In modern anesthesia practice, neuromuscular management does not end with reversal. It ends with quantifiable verification.
Quantitative neuromuscular monitoring allows clinicians to determine the actual degree of neuromuscular blockade, guide reversal dosing appropriately, and confirm recovery before extubation. Technologies such as the TwitchView TOF Monitor provide objective, real-time train-of-four measurements, replacing estimation with measurement.
The difference between a smooth recovery and a postoperative airway event may come down to a simple question: Did we assume recovery, or did we measure it?