Sugammadex is a selective muscle relaxant-binding agent with a modified γ-cyclodextrin structure. This can effectively antagonize aminosteroidal non-depolarizing neuromuscular blocking agents. While anticholinesterase reaches the synaptic cleft and must bind to acetylcholinesterase, sugammadex rapidly encapsulates a free neuromuscular blocking agent in the bloodstream without having to enter the synaptic cleft. After that, a concentration gradient is formed, and the neuromuscular blocking agent diffuses into the bloodstream at the receptor site, causing acetylcholine to recombine with the receptor. Due to the differences in these mechanisms, sugammadex exhibits a rapid onset of action [1]. In addition, sugammadex has no muscarinic effects, and neuromuscular blockade can be effectively reversed by administration of an appropriate amount along with quantitative neuromuscular monitoring during a deep neuromuscular blockade.

In Korea, sugammadex was introduced in the market in 2013. Its clinical usage has gradually increased, with more than one million vials used by 2019. Although rare, several adverse events have been continuously reported.

Therefore, this study aimed to review all reported cases of adverse events associated with the use of sugammadex to date, that have been reported in Korean population, and to suggest a method to reduce adverse events based on the reported cases, as well as a literature review on this subject.

The adverse events associated with sugammadex reported to date include hypersensitivity and anaphylaxis, cardiac arrest, profound bradycardia, incomplete reversal, negative pressure pulmonary edema, vomiting, dry mouth, tachycardia, hypotension, coagulopathy, interactions with steroids, and neuronal damage. These cases have also been reported in Korean populations; nevertheless, the incidence of or mortality due to adverse events has not been analyzed over the nine years of its clinical use in Korea. Based on the frequency of use and number of reported cases, the incidence of adverse events directly caused by sugammadex in Korea is approximately 0.0007%, and no cases of death caused by sugammadex have been reported to date. However, the actual number of cases are estimated to be higher than this. Potential explanations for this are that there may have been cases not analyzed for case reports. Additionally, cases may have been omitted because the causative drug is unclear. In addition, more than two vials may have been prescribed to one patient to reduce the incidence rate. However, even though the incidence rate is not yet high, certain adverse events can be fatal, and efforts are required to detect adverse events early and reduce the incidence rate.

The points of importance from the results include that there were three cases with American Society of Anesthesiologists physical status 3 and two cases with allergy history; sugammadex was administered immediately after surgery and at TOF 0 in several cases, even though neuromuscular monitoring was performed in nine cases; an average of 2.87 mg/kg of sugammadex was administered even though 400 mg was administered in patient 7, and one full vial was used in 6 cases. Currently, 200 mg of sugammadex in one vial is used most commonly in clinical practice. Many practitioners tend to administer the entire 200 mg of sugammadex in one vial, as the remaining amount must be discarded. They also tend to use one full vial to prevent residual neuromuscular block by administering a larger amount than necessary [13]. Of the six cases in which one full vial was used, the use of one vial in a patient weighing 109 kg at TOF 3 was considered appropriate; in three cases, the use of one full vial of sugammadex at TOF 0 was not considered incorrect, but appropriate in consideration of the risk of adverse events. In two cases, the dose of 3.28 mg/kg and 3.13 mg/kg, respectively, without inspection of the TOF after surgery despite TOF monitoring was considered inappropriate. In these two cases, anaphylaxis occurred.

Neuromuscular monitoring provides an easy and effective method to reduce the excessive use of sugammadex. The minimal dose of sugammadex recommended by the manufacturer is 2 mg/kg at a TOF of 2. However, it is sufficient to use less than 2 mg/kg of sugammadex for a TOF of 2 or higher [14]. Therefore, the authors of this study predicted that administering sugammadex appropriately according to the degree of neuromuscular function recovery through quantitative neuromuscular monitoring and avoiding habitual administration of one full vial could effectively reduce the incidence and severity of adverse events. In addition, this can prevent interference in the neuromuscular-blocking effect when re-administering a neuromuscular blocking agent, as reintubation is required after extubation [15].

The most frequent adverse event in this study was anaphylaxis. The main structure of sugammadex, γ-cyclodextrin, is widely used in everyday life as a solubilizer or stabilizer for food and cosmetics. For the average person, the amount of γ-cyclodextrin consumed per day is 4–8.8 g [16]. This may have resulted in sensitization, which caused hypersensitivity to sugammadex. Therefore, even a patient exposed to sugammadex for the first time may exhibit hypersensitivity due to cross-reactivity. Given that two out of five patients with cases of anaphylaxis had a history of allergies, a history of allergy itself may also help predict the occurrence of anaphylaxis. Anaphylaxis for sugammadex is thought to be mostly associated with IgE-mediated hypersensitivity (type 1 hypersensitivity). Therefore, as a diagnostic test, a skin test such as intradermal testing and skin prick test, and a tryptase test that can determine the activation of mast cells may be helpful [17]. Recently, it has been found that hypersensitivity not related to sugammadex-specific IgE or IgG exists. There are reports that anaphylaxis is caused by sugammadex-rocuronium complex and sugammadex molecules together, and not by the sugammadex molecule itself [18]. Unlike that of other drugs, the hypersensitivity reaction to sugammadex is dose-related. According to Min et al., no anaphylaxis occurred in 151 patients administered 4 mg/kg, but one case of anaphylaxis occurred in 148 patients administered 16 mg/kg [19]. Anesthesiologists should always be aware that anaphylaxis may occur within 10 min of sugammadex administration, even in patients with no allergic history in the past, and the relationship with the dose should also be considered.

Sugammadex is known to cause a third-degree atrioventricular block, QT prolongation, and coronary vasospasm, leading to profound bradycardia and cardiac arrest [20]. Such complications occurred in healthy patients with no underlying cardiac diseases. In Korea, cardiac arrests have occurred in a patient with no underlying cardiac disease or symptoms other than atypical chest pain [8]. Importantly, the severity may increase in proportion to the dose, as the cardiovascular effect of sugammadex is associated with free sugammadex molecules [21]. Therefore, in all patients administered sugammadex, cardiovascular monitoring must be performed for at least 10 min after administration, with appropriate dosing of sugammadex.

Negative pressure pulmonary edema is thought to have occurred due to rapid recovery of respiratory force due to administration of sugammadex in the presence of upper airway collapsibility, such as laryngospasm [22]. When a large inspiratory force is applied in the state of obstruction in the upper airway, a large intrathoracic negative pressure is created to increase the blood flow to the pulmonary vasculature. As a result, pulmonary edema may occur due to an excessive increase in hydrostatic pressure and distension of the pulmonary vessel [23]. Even in this case, excessive use of sugammadex could be problematic. The reason for this is that if laryngospasm is severe, it may be necessary to administer an additional neuromuscular blocker for reintubation [24]. At this time, free sugammadex molecules may interfere with neuromuscular blockade. Therefore, in this case, another type of neuromuscular blocking agent should be used. In addition, when excessive sugammadex is administered, T4 recovery is faster than expected, before T1 recovery, and the TOF ratio may increase, leading to errors in judgment [25]. From another point of view, negative pulmonary edema can also occur due to residual neuromuscular block. Inspiratory muscles, such as the diaphragm, are resistant to neuromuscular block agents and tend to be blocked less intensively or recover faster. Therefore, the onset and offset of neuromuscular blocking agents are more rapid [26]. Eikermann et al. reported that four patients displayed upper airway obstruction in the state of minimal residual neuromuscular block at a TOF ratio of 0.83 ± 0.06. This is because inspiratory muscles are less susceptible to curarization than expiratory muscles [27]. Negative pulmonary edema is also predicted to occur because of such an imbalance. Therefore, anesthesiologists should keep in mind that negative pressure pulmonary edema can occur due to residual neuromuscular block as well as rapid recovery by sugammadex and should focus on maintaining airway patency.

In two cases of incomplete recovery, there were underlying neuromuscular diseases (amyotrophic lateral sclerosis and Duchenne muscular dystrophy). In both cases, sugammadex was administered at TOF 0, and the time to extubation after sugammadex administration was 15.6 min and 15 min, respectively. However, the presence of neuromuscular diseases does not necessarily cause delayed recovery [28], and although rare, delayed recovery may occur in healthy patients [29]. Since these patients may also experience additional adverse events due to excessive sugammadex, determining the appropriate dose of sugammadex through quantitative neuromuscular monitoring will help prevent adverse events.

This study has several limitations. First, as the number of cases was small due to difficulties in obtaining the data; therefore, there may have been insufficient power to detect statistical significance. However, even based on the cases reported so far, increased attention to the monitoring of neuromuscular function and patients’ vital signs in conjunction with the use of sugammadex seems to be effective in reducing the incidence and severity of adverse events. Second, it was not known whether neuromuscular monitoring was performed after surgery. There was no mention of residual paralysis in any of the ten cases. Since the authors of this study aimed to suggest the administration of sugammadex at an appropriate dose, such a suggestion may have been better supported if stability against residual paralysis was ensured by postoperative neuromuscular monitoring.

In conclusion, a review of the cases of adverse events directly caused by sugammadex in the Korean population shows that the incidence and severity of adverse events could be reduced through routine neuromuscular monitoring and careful administration of sugammadex [14]. In addition, sufficient recovery time as well as monitoring is required until extubation after administration [20]. Recently, sugammadex dose-ranging studies based on cost-saving strategies have been conducted. These studies commonly emphasize quantitative neuromuscular monitoring to prevent residual neuromuscular block [30]. A better guideline for sugammadex administration is required to contribute not only to cost-effectiveness but also to the reduction of adverse effects.