Although neuromuscular blockade is less commonly used in pediatric anesthesia, the incidence of residual paralysis in children is comparable to adults, potentially reaching 48% [1, 2]. The developing respiratory anatomy and physiology of pediatric patients may increase their susceptibility to respiratory complications from residual neuromuscular blockade, especially in infants and neonates [2]. Respiratory adverse events account for more than three-quarters of all critical incidents during pediatric anesthesia and approximately half of unplanned admissions to the pediatric intensive care unit (PICU). Infants under one year of age exhibit an odds ratio for critical incidents four times greater than older children [3].

Case Report: Residual Neuromuscular Blockade in a Pediatric Patient Following a Single Dose of Rocuronium and Reversal with Sugammadex

We present a case of residual neuromuscular blockade observed in a 6kg, 2-month-old following a 1.5-hour general surgical procedure. Anesthesia was induced with a 7% inspired concentration of sevoflurane, and a 1 mg/kg dose of rocuronium was administered to facilitate endotracheal intubation, with no additional administration of rocuronium thereafter. Upon completion of surgery, the patient was reversed with 20 mg of sugammadex. After 8 minutes, the infant exhibited adequate tidal volumes and demonstrated significant strength on clinical exam. With the clinical criteria for recovery met, the patient was extubated and transferred to the post-anesthesia care unit (PACU). In the PACU, the infant grew increasingly agitated and inconsolable.

Figure 1: The patient's foot is shown with the TwitchView electromyography (EMG) electrode facilitating real-time monitoring of neuromuscular function. (Source: author)

Quantitative train-of-four (TOF) measurements were obtained post-operatively using the TwitchView train of four monitor. Upon arrival in the PACU, a TOF ratio of 36% was measured at the flexor hallucis brevis (Figure 2). Six minutes later, the TOF ratio had not improved, and the patient’s oxygen saturation levels dropped below 90%. Recognizing that residual neuromuscular weakness could be responsible for the hypoxemia, an additional dose of 2 mg/kg sugammadex was promptly administered. Following this intervention, the patient's TOF ratio steadily increased to 91% (Figures 2 and 3). Within minutes, her clinical condition improved; the patient stopped crying, her oxygen saturation levels returned to baseline, and she successfully accepted oral feeding with a bottle. 

 
Figures 2: On left, TwitchView measures a TOF ratio of 36% upon arrival to the PACU. On right, TwitchView measures a TOF ratio of 91% following the administration of a 2mg/kg rescue dose of sugammadex. Notably, a marked increase in electromyographic (EMG) amplitude and a reduction in fade are observed after the rescue reversal. (Source: author)

Hypoxemia, defined as peripheral oxygen saturation (SpO2) less than 90%, is an early indication of respiratory complications. In a 5-month review of 3,840 patients undergoing elective surgery at a pediatric hospital, 4.35% of patients experienced hypoxemia in the PACU [4]. Infants, due to their smaller functional residual capacity (FRC) and higher metabolic demands, are particularly susceptible to rapid desaturation in the event of airway compromise [5].

Figures 3: The TwitchView train-of-four monitor trend plot illustrates approximately 10 minutes of plateaued recovery in the PACU, followed by a steady increase in the TOF ratio to 91% following the administration of a sugammadex rescue dose. (Source: author)

Why Did the Patient Meet Extubation Criteria If Residual Neuromuscular Blockade Was Present?

Faulk et al. demonstrated that qualitative train-of-four assessments utilizing a peripheral nerve stimulator, in conjunction with clinical evaluations, fail to detect residual muscle weakness in 30% of pediatric patients aged 2 to 17 years [6]. A 2021 survey of members of the Society of Pediatric Anesthesia (SPA) indicated that only 40% of practitioners routinely perform train-of-four assessments, with anesthesiologists who primarily use sugammadex conducting train-of-four assessments less frequently [7]. As with the case presented herein, pediatric anesthesia providers often rely on observed spontaneous movements and ventilatory parameters to “assess strength” in infants because infants are unable to follow commands. 

Ventilatory parameters are unreliable indicators of recovery, particularly in infants, whose diaphragms exhibit greater resistance to neuromuscular blocking agents and recover more rapidly under deeper levels of neuromuscular blockade [2, 8]. Although the diaphragm demonstrates quicker recovery, the effective dose required to achieve 95% twitch suppression (ED95) of rocuronium is significantly lower in infants than in older children. Moreover, the duration of effect following a standard 0.6 mg/kg intubation dose of rocuronium is longer in infants compared to older children (42 minutes vs. 27 minutes) [2, 9, 10]. Unlike the diaphragm, the upper airway muscles are among the most sensitive to neuromuscular blocking agents exhibiting the slowest recovery. For this reason, postoperative residual neuromuscular blockade often presents as upper airway obstruction [2, 3, 4, 5]. Monitoring the adductor pollicis with a quantitative neuromuscular monitor ensures adequate recovery is achieved and allows for individualized patient care, particularly in high-risk patients like infants who exhibit higher sensitivity and more unpredictable responses to neuromuscular blocking agents [2, 6, 7, 11].

Inadequate Doses of Sugammadex Can Result in Residual Neuromuscular Blockade

In a prospective, dose-finding study of adult patients, Bowdle et al. investigated the hypothesis that many patients could achieve adequate reversal with less than the manufacturer’s recommended dose of sugammadex, while a subset would require more. Among the 97 patients evaluated, 87% of patients (who received sugammadex) achieved adequate reversal (TOF Ratio ≥90%) below the label-recommended dosing. Of note, 13% of patients required doses exceeding the manufacturer's guidelines to achieve adequate recovery [12]. Inadequate reversal can result in significant complications, including respiratory insufficiency, aspiration pneumonia, prolonged hospital stays, and increased healthcare costs [1, 2, 11]. Bowdle’s findings, alongside the case presented, highlight the critical need for quantitative monitoring whenever a non-depolarizing neuromuscular blocking agent is administered.

Ozgen comments on the need to change standardized reversal and assessment practices during pediatric anesthesia.