Train-of-four Response Research Articles

Intraoperative electromyographic monitoring in children using a novel pediatric sensor.

Train-of-four (TOF) monitoring is essential in optimizing perioperative outcomes as a means to assess the depth of neuromuscular blockade and confirm recovery following the administration of neuromuscular blocking agents (NMBAs). Quantitative TOF monitoring has been limited in infants and children primarily due to lack of effective equipment. The current study evaluates a novel electromyography (EMG)-based TOF monitor with a recently developed pediatric-sized self-adhesive sensor in infants and children. Consented pediatric patients undergoing inpatient surgery requiring the administration of NMBAs were enrolled. The EMG electrode was placed along the ulnar nerve on the volar aspect of the distal forearm. The muscle action potentials from the adductor pollicis muscle were recorded throughout surgery at 20-second intervals. Data from the monitor's built-in memory card were later retrieved and analyzed. The final study cohort included 51 patients who ranged in age from 0.2 to 7.9 years and in weight from 4.2 to 36.0 kilograms. Thirty patients weighed less than 15 kgs. Supramaximal stimulus current intensity (mA) at a pulse width of 200 μsec was 30 mA in 8%; 40 mA in 29%; 50 mA in 16%; and 60 mA in 20% of the patients. Supramaximal stimulus current intensity (mA) at a pulse width of 300 μsec was 50 mA in 4%; 60 mA in 24%. The muscle action potential baseline amplitude was 8.7 ± 3.3 mV and recovered to 7.2 ± 3.7 mV after antagonism of neuromuscular blockade. The average baseline TOF ratio was 100 ± 3% and recovered to 98 ± 7% after antagonism of neuromuscular blockade. No technical issues were noted with application of the sensor or subsequent use of the monitor. Neuromuscular monitoring can be performed intraoperatively in pediatric patients who are less than 8 years of age using a novel commercially available EMG-based monitor with a recently developed pediatric sensor. The novel sensor allows use of an EMG-based monitor in infants and children in whom acceleromyography or subjective (visual) observation of the TOF response may not be feasible. Automatic detection of neuromuscular stimulating parameters (supramaximal current intensity level, baseline amplitude of the muscle action potential) was feasible in pediatric patients of all sizes including those weighing less than 15 kilograms or when there was limited access to the extremity being monitored.

Comparison of Train of Four Measurements with Kinemyography NMT DATEX and Accelerography TOFscan.

Introduction: This study was designed to compare the Datex neuromuscular transmission (NMT) kinemyography (NMTK) device with the TOFscan (TS) accelerometer during the onset and recovery of neuromuscular blockade. Patients and methods: This prospective study included adult patients who were scheduled to undergo elective surgery with general anesthesia and orotracheal intubation. The TS accelerometer was randomly placed at the adductor pollicis on one hand, and the NMTK was placed on the opposite arm. Anesthesia was initiated with remifentanil target-controlled infusion (TCI) and 2.0–3.0 mg/kg of propofol. Thereafter, 0.5 mg/kg of atracurium or 0.6 mg/kg of rocuronium was injected. If needed, additional neuromuscular blocking agents were administered to facilitate surgery. First, we recorded the train of four (TOF) response at the onset of neuromuscular blockade to reach a TOF count of 0. Second, we recorded the TOF response at the recovery of neuromuscular blockade to obtain a T4/T1 90% by both TS and NMTK. Results: There were 32 patients, aged 38–83 years, with the American Society of Anesthesiologists (ASA) Physical Status Classification I–III included and analyzed. Surgery was abdominal, gynecologic, or head and neck. The Bland and Altman analysis for obtaining zero responses during the onset showed a bias (mean) of 2.7 s (delay) of TS in comparison to NMTK, with an upper/lower limit of agreement of [104; −109 s] and a bias of 36 s of TS in comparison to NMTK, with an upper/lower limit of agreement of [−21.8, −23.1 min] during recovery (T4/T1 > 90%). Conclusions: Under the conditions of the present study, the two devices are not interchangeable. Clinical decisions for deep neuromuscular blockade should be made cautiously, as both devices appear less accurate with significant variability.

Neostigmine: Mechanism of Action, Dosing, and Factors Determining Adequacy of Recovery Following Administration

The endpoint of adequate neuromuscular recovery allowing for safe extubation has been revised several times. A train-of-four (TOF) ratio of at least 0.9 measured at the adductor polices muscle is required to exclude clinically relevant residual paralysis. In particular, upper airway muscle integrity, the hypoxic ventilatory response, and swallowing are still impaired at shallow degrees of residual paralysis. The aim of this review is to evaluate the efficacy of neostigmine in achieving this higher benchmark. Recent findings suggest that (a) the administration of neostigmine should be delayed until advanced degrees of pre-reversal recovery have occurred (i.e., T1 > 25% or the fourth response to TOF stimulation), or recovery intervals over 15 min have to be accepted; (b) small concentrations of neostigmine (i.e., 20–30 μg/kg) are effective in antagonizing shallow degrees of residual paralysis; and (c) the appropriate administration of neostigmine (i.e., dosing based on monitoring) reduces postoperative complications and improves neuromuscular recovery. When 40–70 μg/kg neostigmine are administered at the return of 1–4 TOF responses, a recovery interval over 20 min can be expected. Increasing the dose of neostigmine will not further accelerate this interval, but it may increase the risk of paradoxical effects (i.e., the reappearance of fade). A shorter recovery interval is obtained when neostigmine-based reversal is given at more advanced spontaneous pre-reversal neuromuscular recovery.

Intubating Conditions with three different doses of Rocuronium in surgery of cancer patients

Background: This is a prospective randomized, double blind study to determine the doses of rocuronium that would give 90% and 95% probabilities of successful tracheal intubation within 60s after administration. This study evaluated intubating conditions and duration of action of 0.4 mg, 0.8 mg and 1.2 mg of rocuronium, administered intravenously in patients undergoing elective surgical procedures. Goal in this study is to define doses level of rocuronium that would provide optimal relaxation for tracheal intubation in patients in whom succinylcholine was relatively contraindicated.
 Methods: Sixty patients both male and female, ASA I & II, age between 18–60 years, with BMI of less that 30 who were planned for elective surgical procedures were randomized into three groups. Group A received 0.4 mg (n=20), Group B received 0.8 mg (n=20) and Group C received 1.2 mg (n=20) of rocuronium. At 60 seconds after injection of the rocuronium, laryngoscopy was initiated, with the goal being endotracheal tube passed through the patient's vocal cords and the cuff inflated within the trachea in 20s. Intubating conditions was graded excellent, good or poor according to Cooper scoring system criteria. When the patient lost consciousness, train-of-four (TOF) stimulation (at 2 Hz and repeated every 12s) were recorded. Immediately after tracheal intubation and every 5 min thereafter the investigator counted the number of tactile TOF responses. The duration of action of rocuronium was defined as the time from the end of injection of rocuronium until reappearance of first tactile response to TOF stimulation.
 Results: There were twelve patients in the 0.4mg/kg rocuronium group, two in the 0.8mg/kg group, and one in the 1.2mg/kg rocuronium group with an unacceptable intubation grade caused by sustained coughing at intubation. The D90 and D95 doses were 0.83(0.59 -1.03) and 1.04 (0.76-1.36) mg/kg, respectively. Estimated time until first tactile train-of-four response after D50 and D95 doses were 43min and 52 min, respectively.
 Conclusion: After induction with pethedine and sodium thiopentone, rocuronium in a dose of 0.8mg/kg produces equivalent intubating conditions as that of 1.2mg/kg after 60 seconds of administration

A Comparision of the Effect of Sugammadex on the Recovery Period and Postoperative Residual Block in Young Elderly and Middle-Aged Elderly Patients.

The importance of the characteristics of anesthesia and postoperative residual curarization (PORC) in the elderly population should be a growing concern in this century. To investigate the effect of sugammadex on the duration of the recovery from neuromuscular blocking agents and postoperative residual curarization in the young elderly and middle-aged elderly patients who underwent elective laparoscopic cholecystectomy, followed by a train of four (TOF) watch monitorization. Prospective clinical trial study. Sixty patients over the age of 65 with American Society of Anesthesiologists I-III were divided into two groups according to their age (65-74 years old and ≥75 years old). Patients received sugammadex (2.0 mg/kg iv) at the reappearance of the second twitch of the TOF as an agent for reversal of neuromuscular blockage at the end of surgery. Patients were extubated at the time of TOF ≥0.9. The patients' TOF responses were evaluated with regards to PORC in at the 5th minute and were followed up for one hour in the recovery room. Reintubation was applied for those patients who developed PORC and had peripheric oxygen saturation <90% despite being given 6 L oxygen per min with a face mask. The onset time of neuromuscular blocking agent and time from T2 to achieve TOF ratio 90% (the duration of sugammadex effect) or over were found to be longer in the middle-aged elderly group than in the young elderly group. A statistically significant relationship was found between age and the duration of TOF ratio to reach 0.9 in the same direction. The PORC incidence and rate of reintubation were found to be 1.7% in all patients. In our opinion, it is necessary to remember that the duration of sugammadex effect on the recovery period is prolonged for patients who are aged ≥75 years compared to patients aged between 65-74 years. (ClinicalTrials.gov Identifier: ACTRN12615000758505).

Performing post-tetanic count during rocuronium blockade has limited impact on subsequent twitch height or train-of-four responses.

Waiting five to six minutes before measuring a train-of-four (TOF) after a 50-Hz tetanic stimulation or post-tetanic count (PTC) in order to allow the facilitation of transmission to subside is commonly recommended but is based on limited evidence. The purpose of this study was to measure the TOF responses after PTC in one hand and to compare the responses with those in the contralateral (control) hand. Twenty-two adult patients undergoing elective surgery under opioid-desflurane anesthesia were fitted with sensors to measure displacement of their thumbs in response to ulnar nerve stimulation. Rocuronium 0.6 mg·kg(-1) was administered and TOF stimulation was applied to both sides. One side was randomized to PTC (50-Hz tetanus followed by a three-second pause and 15 1-Hz stimuli) when the opposite (control) side recovered to 10% first twitch (T1) height. Train-of-four stimulation was continued bilaterally every 20 sec until 30 min after PTC. Comparisons of the T1 and TOF ratio (T4/T1) were made at two, five, ten, 20, and 30 min. The mean (standard deviation [SD]) T1 value in the PTC arm was 11.8 (7.1)% just before PTC. The T1 values were significantly greater in the PTC arm at two, five, and ten minutes, with mean (SD) differences of 6.3 (6.7)%, 9.4 (6.8)%, and 7.4 (3.9)%, respectively (P = 0.008). There were no significant differences in T1 values between groups at 20 and 30 min, and no statistically significant differences in T4/T1 values at any time. A small but clinically insignificant increase in T1 is seen for at least ten minutes after PTC without any detectable change in T4/T1 values. The TOF responses are reliable as early as one minute after PTC.

Rocuronium pharmacokinetics and pharmacodynamics in the adductor pollicis and masseter muscles.

The aim of this study was to characterize the dose-effect relationship of rocuronium at the adductor pollicis and masseter muscles. Ten, ASA I, adult patients, received a bolus dose of rocuronium 0.3 mg/kg during propofol based anesthesia. Train-of-four (TOF) was simultaneously monitored at the masseter and the adductor pollicis muscles until recovery. Rocuronium arterial serum concentrations were measured during 120 min. The first twitch of the TOF response was used to characterize the time-effect profile of both muscles using pharmacokinetic-pharmacodynamic analysis in NONMEM. A decrease in NONMEM objective function (∆OFV) of 3.84 points for an added parameter was considered significant at the 0.05 level. Onset time at the masseter (mean ± SD, 1.5 ± 0.9 min) was faster than at the adductor pollicis (2.7 ± 1.4 min, P < 0.05). Recovery, measured as the time to TOF ratio = 0.9 was similar between muscles 29.9 ± 6.7 (adductor pollicis) vs. 29.3 ± 8.1 (masseter). (P = 0.77). The estimated pharmacodynamic parameters [mean (95% CI)] of the adductor pollicis muscle and the masseter muscle were; plasma effect-site equilibration half-time (teq) 3.25 (2.34, 3.69) min vs. 2.86 (1.83, 3.29) min, (∆OFV 383.665); Ce50 of 1.24 (1.13, 1.56) mg/l vs. 1.19 (1.00, 1.21) mg/l, (∆OFV 184.284); Hill coefficient of 3.97 (3.82, 5.62) vs. 4.68 (3.83, 5.71), (∆OFV 78.906). We found that the masseter muscle has faster onset of blockade and similar recovery profile than adductor pollicis muscle. These findings were best, explained by a faster plasma effect-site equilibration of the masseter muscle to rocuronium.

Response to rocuronium and its determinants in patients with myasthenia gravis: A case-control study.

Several previous studies using univariate analysis have suggested that the pre-anaesthetic train-of-four (TOF) ratio, concentration of anti-acetylcholine receptor (AChR) antibodies and the presence of preoperative generalised muscular involvement are determinants of an increased response to neuromuscular blocking agents (NMBAs) in patients with myasthenia gravis. However, the determinants of the response of patients with myasthenia gravis to rocuronium, which is expected to be used more frequently since the advent of sugammadex, have not been studied. To clarify whether previously suggested determinants of the response to other intermediate-acting NMBAs would also affect the response to rocuronium and to reveal the determinants of the increased response to rocuronium in individual patients with myasthenia gravis using multivariate analysis. Case control study. Kumamoto University Hospital, November 2010 to September 2013. Thirty-eight patients with myasthenia gravis having surgery using a total intravenous anaesthetic technique were investigated. After induction of general anaesthesia, the 95% effective dose (ED95) of rocuronium was calculated using cumulative dose-finding methods. Neuromuscular function was monitored by acceleromyographic assessment of TOF responses of the adductor pollicis muscle to ulnar nerve stimulation. Patients were then divided into the increased response (ED95 <0.15 mg kg, n = 13) and non-increased response groups (ED95 ≥0.15 mg kg, n = 25). Demographic data, TOF ratio before rocuronium injection (baseline TOF ratio), concentration of anti-AChR antibodies, Osserman classification and treatment for myasthenia gravis in the two groups were compared. Stepwise logistic regression identified baseline TOF ratio and age of onset of myasthenia gravis as determinants of the increased response to rocuronium in patients with myasthenia gravis [odds ratios (95% confidence interval) of 0.87 (0.77 to 0.98; P = 0.02) and 0.92 (0.86 to 0.99; P = 0.03), respectively]. Multivariate analysis identified baseline TOF ratio and age of disease onset as determinants of the increased response to rocuronium in patients with myasthenia gravis. Registered with UMIN Clinical Trials Registry, identifier: UMIN000006766.

Cisatracurium degradation: Intravenous fluid warmer the culprit?

Cisatracurium degradation: Intravenous fluid warmer the culprit?

Influence of neuromuscular block and reversal on bispectral index and NeuroSense values

Influence of neuromuscular block and reversal on bispectral index and NeuroSense values

In Reply:

We thank Dr. Caruso for his comments related to our observational study reporting a substantially increased risk of postoperative residual paralysis in patients having qualitative train-of-four (TOF) monitoring of eye muscles compared with those monitored at the adductor pollicis.1 Reversal of neuromuscular blockade before extubation was assessed clinically as per routine care. Due to the observational nature of the study, we did not standardize what clinical tests that may have been used. We agree with Dr. Caruso that subjective assessment of the response to nerve stimulation, and of clinical tests, is inadequate to confirm successful reversal.Although the presumed mechanism behind the association of monitoring site and residual paralysis would be a more generous administration of neuromuscular-blocking drugs to patients with monitoring of eye muscles, we did not observe differences in neuromuscular-blocking drugs dosing. It is conceivable that patients in the eye muscle monitored group would have had lower adductor pollicis TOF-counts at the time of neostigmine administration, had such assessments been made. The degree of spontaneous recovery at the time of reversal has repeatedly been shown to be a major determinant of successful timely reversal. Studies such as those by Kim et al.2 and Kirkegaard et al.3 clearly demonstrate the critical importance of spontaneous recovery and form the basis for current recommendations to administer reversal only after a TOF count of 4 has been achieved.4 These studies, and current recommendations for clinical practice, are based on monitoring of the adductor pollicis. As there were no simultaneous assessments of the TOF response at both sites, this explanation remains speculative in our data.Dr. Caruso mentions that depending on intensity of the block, reversal may take up to 50min. Such a delayed reversal is rare if TOF-monitoring is used at the adductor pollicis to guide the appropriate administration of neostigmine. We believe that the administration of neostigmine earlier than approximately 10min before anticipated extubation is not optimal. This is because peak effect of neostigmine’s inhibition of anticholinesterase is achieved by 10min.5 We agree with Dr. Caruso that before extubation, optimal management would include the objective assessment of neuromuscular function, and extubation should be deferred until residual paralysis is not detected. If the TOF-ratio has not reached 0.90, 10min after neostigmine administration, it is unlikely that this is the result of delayed administration of neostigmine. Rather, the explanation is more likely to be that the sufficient spontaneous recovery was not achieved before administration of neostigmine. When discussing about earlier administration of reversal, at deep levels of block and using qualitative monitoring, Kopman et al.6 stated that this practice “places the patient at risk and the anesthetist in the dark”. Early administration of neostigmine will prolong the postreversal amount of time with a TOF-ratio in the range 0.4–0.9 and a TOF-count of 4 without fade (referred to as the “zone of blind paralysis” by Plaud et al.4) and will not shorten the time to full reversal.7 An additional disadvantage of too early administration of neostigmine is that the patient will not have the benefit of maximal effect (i.e., maximal acetylcholinesterase inhibition) at time of extubation.5,8Accomplishing full reversal of paralysis is often challenging but more likely to be successful if guided by published data on administration of neostigmine after assessment of TOF-monitoring at the adductor pollicis. We therefore completely agree with Dr. Donati who wrote the editorial accompanying our report: “In practice, reversal and recovery should be guided by adductor pollicis response, and if needed, a switch from facial to ulnar nerve stimulation should be accomplished at the end of the surgical procedure.”9

Postoperative pulmonary edema in a patient with POEMS syndrome

Postoperative pulmonary edema in a patient with POEMS syndrome

Anaesthesia and orphan disease

Huntington’s disease is an autosomal dominant disorder that affects the basal ganglia with a prevalence of four to 10 per 100 000 people. Onset is typically between 30 and 50 years of age. There is also a juvenile onset of the disease wherein the symptoms begin before aged 20; this occurs in 10% of affected persons. This latter group is more prone to seizures, has impaired glucose metabolism and often inherits the disease in a sex-linked manner from the father. Genetic tests can confirm the diagnosis, even prenatally. Symptoms include choreic movements, personality disorders and impairment of swallowing and gag reflexes. The anaesthetic management of a patient with Huntington’s disease provides particular challenges due to the risk of pulmonary aspiration and altered responses to anaesthetic drugs. Prolonged apnoea of between 1 and 2 h has been reported after the use of thiopentone and suxamethonium, and there is an increased sensitivity to anticholinergics. Whether these patients have low levels of atypical pseudocholinisterases remains unanswered. We know of no previous reports of the use of sugammadex in the anaesthetic management of patients with Huntington’s disease. We have obtained the patient’s written consent for publication of this case report.

A Train-of-Four Count Should Be a Train-of-Four Count, Independently of the Method It Was Determined With

To the Editor: We read with interest the article from Murphy et al. entitled “Intraoperative Acceleromyography Monitoring Reduces Symptoms of Muscle Weakness and Improves Quality of Recovery in the Early Postoperative Period.”1Indeed, the authors confirmed previous findings that objective acceleromyographic neuromuscular monitoring may improve perioperative neuromuscular management.2In the current study this improved perioperative management led to a better spontaneous recovery at the time of neostigmine administration: 61 of 76 patients in the acceleromyographic group compared with 41 of 74 patients in the control group had a train-of-four (TOF) count of 4 when neostigmine was given: P = 0.014. However, it is well known that the degree of spontaneous recovery at the time of neostigmine administration may have a major effect on neostigmine‘s efficacy. In this context Kirkegaard et al. 3reported that 20 min after the administration of neostigmine 70 μg/kg−1at a TOF count of 4 the incidence of residual paralysis (defined as a TOF ratio less than 0.9) was 25%. This incidence increased to 56% when neostigmine was given at a TOF count of 2 instead of 4 without changing any of the other parameters.3Unfortunately, the timing of neostigmine administration was hardly controlled in the trial by Murphy et al. 2and therefore some points seem quite unclear to us: first, according to the Methods section neostigmine should be given when a TOF count of at least 3 was present. In the Results section, however, the TOF count at the time of neostigmine administration ranged from a TOFcount between 0 and 4. Second, and as mentioned previously, the number of patients who had a TOF count of 4 at this time was increased by 30% in the acceleromyographic group versus control. Murphy et al. found a significant difference in repeat doses of rocuronium between the two groups during the last 45 min of the surgical procedure, a finding that is supposed to explain the effect in the acceleromyographic group. As stated in the Methods section, participating anesthesiologists were allowed to use “TOF ratio data to guide neuromuscular blocking agents dosing when surgical relaxation was not longer required.” The authors are requested to provide some information about the management of neuromuscular blocking agents dosing in the control group during this period. Third, most patients (102 of 150) had 4 TOF responses at the moment of neostigmine administration. It is not obvious whether these patients all had a simple TOF count of 4 (4 responses present with the first response less than 20%; the TOF-Watch SX®[Bluestar Enterprises, Omaha, NE] display shows the TOF count) or whether recovery was even more advanced in some patients (still 4 responses present but the first response more than 20%; the TOF-Watch SX® calculates and shows the TOF ratio). Further, it should be reported if and how this distinction was made in the control group. Finally, it would be interesting to know if all patients received a standard dose of 50 μg/kg−1neostigmine, even in case of a deeper residual block with less than three twitch responses. Some information about the real doses of neostigmine that have been used could be helpful in this context.Based on the information provided, we must conclude that the difference in symptoms of muscle weakness and improved quality of recovery observed in this study could simply be the consequence of the dose or the timing of the administration of neostigmine rather than the direct consequences of intraoperative acceleromyographic monitoring as supposed by Murphy et al. We suggest that the authors should complete the missing information and report the incidence of residual blockade and associated unpleasant symptoms of muscle weakness separately according to the patients' individual TOF count at the time of neostigmine administration to clarify this key issue. In our opinion, these data are essential for the reader to allow a correct interpretation of the results and, thus, to improve patient's safety. Moreover, it would be very instructive to see whether there were any significant differences in unpleasant symptoms if neostigmine was given at TOF count of 4 independently from the technique of determination (acceleromyographic or conventional qualitative monitoring, respectively), as supposed by Murphy et al. Currently, we are in doubt about this issue.In addition, the number of included patients reported in the “What This Article Tells Us That Is New” section is probably incorrect and should be 155 instead of 115.

Continuous Infusion versus Intermittent Bolus Dosing of Vecuronium in Patients Receiving Therapeutic Hypothermia After Sudden Cardiac Arrest

To compare the effects of vecuronium administered as an intravenous continuous infusion versus intermittent bolus doses in patients treated with therapeutic hypothermia after sudden cardiac arrest (SCA). Design. Retrospective medical record review. Cardiac care unit of a university-affiliated, level I trauma center. Of 123 adults treated with therapeutic hypothermia after SCA, 80 received continuous-infusion vecuronium 0.8 μg/kg/minute started 2 hours after cooling began or if shivering occurred (January 1, 2004-December 31, 2007), and 43 received intermittent boluses of vecuronium 0.05 mg/kg every 2 hours (January 1, 2008-September 30, 2009). The degree of neuromuscular blockade was measured with a train-of-four (TOF) test. Primary outcomes evaluated were time to achieve goal TOF response and percentage of time the TOF response was maintained at goal. Secondary outcomes included total daily dose of vecuronium, the vecuronium dose needed to achieve goal TOF response, percentage of TOF measurements above or below goal, and time to return of spontaneous respirations and time to extubation after the last dose of vecuronium. The goal TOF response was achieved significantly earlier in the bolus group than the continuous-infusion group (mean 5.9 vs 11.3 hrs, p=0.008). The mean total daily dose of vecuronium administered in the bolus group was significantly lower than that in the continuous-infusion group (51.7 vs 76.9 mg, p=0.002). The mean percentage of TOF measurements above goal was higher in the continuous-infusion group (33% vs 16%, p<0.0001), and the mean percentage of TOF measurements below goal was higher in the bolus group (43% vs 29%, p<0.0001). The median time to return of spontaneous respirations (6 vs 11 hrs, p=0.017) and time to extubation (29.5 vs 89.5 hrs, p<0.0001) were significantly shorter in the continuous-infusion group than the bolus group. Intermittent boluses of vecuronium were more effective in reaching a goal TOF response earlier compared with continuous-infusion vecuronium in patients treated with therapeutic hypothermia. The two dosing strategies were equally effective at maintaining a goal TOF response despite patients receiving a significantly lower daily dose of vecuronium in the intermittent-bolus group.

Recurarization after sugammadex reversal in an obese patient

We report a case that involved immediate postoperative respiratory failure necessitating tracheal intubation, which was possibly related to recurarization after sugammadex reversal. A 54-yr-old woman weighing 115-kg was scheduled for laparoscopic repair of abdominal dehiscence under general anesthesia. Muscle relaxation was induced and maintained with rocuronium (170mg iv total dose). At the end of the 170-min procedure, two twitches were visualized after supramaximal train-of-four (TOF) stimulation at the adductor pollicis muscle, and the patient's central core temperature was 35.6°C. Sugammadex 200mg iv (1.74mg·kg(-1)) was administered. With the patient fully awake, a TOF ratio 0.9 was obtained five minutes later. The tracheal tube was then removed, and the patient was transferred to the postanesthesia care unit. Ten minutes later, the patient presented respiratory failure necessitating tracheal intubation and sedation with propofol. One TOF response only was visualized at the adductor pollicis muscle. Another dose of sugammadex 200mg iv was administered. Forty-five minutes later, the patient was fully awake and her trachea was extubated after repeated measures of the TOF ratio (≥0.9) at the adductor pollicis muscle. The patient fully recovered without sequelae, further complication, or prolonged hospital stay. Shortly after tracheal extubation, an obese patient experienced respiratory failure necessitating tracheal intubation and an additional dose of sugammadex. This occurred despite initial reversal of neuromuscular blockade with an appropriate dose of sugammadex 2mg·kg(-1) iv given at two responses to TOF stimulation.

TOF count at corrugator supercilii reflects abdominal muscles relaxation better than at adductor pollicis

A recovery profile from neuromuscular block similar to that of abdominal (AB) muscles, but different to that of the adductor pollicis (AP) muscle, has been demonstrated at the corrugator supercilii (CSC) muscle. We hypothesized that neuromuscular transmission (NMT) monitoring of CSC might provide useful information on AB relaxation compared with AP. We compared the visual estimation of NMT at CSC and AP with electromyographic measurements of AB during recovery from a vecuronium block. Ten adult patients were studied during balanced anaesthesia. After induction of anaesthesia and tracheal intubation without neuromuscular blocking agents, supramaximal stimulations were applied to three nerves: left 10th intercostal, ulnar, and facial. Electromyographic activity (EMG) of AB was measured (ABemg). After a bolus dose of vecuronium 0.1 mg kg-1, an independent observer blinded to the EMG measurements counted visually detectable train-of-four (TOF) responses at CSC and AP. Values of ABemg associated with 1 to 4 TOF responses at CSC and AP were compared. Values are means (sd). Reappearance of the first and second TOF responses at CSC occurred significantly (P<0.05) earlier and at lower ABemg recovery than that of AP [35 (8) and 41 (9) min vs 51 (10) and 56 (12) min; and 17 (8) and 26 (9)% vs 56 (10) and 75 (11)%, respectively]. We demonstrated that the TOF response count at the CSC, compared with the AP, allowed a better quantification of the degree of AB muscle relaxation during recovery from vecuronium block.

A Temporary Decrease in Twitch Response During Reversal of Rocuronium-Induced Muscle Relaxation with a Small Dose of Sugammadex

We present a case in which a temporary decrease in train-of-four (TOF) response was observed after reversal of muscle relaxation with a small dose (0.5 mg/kg) of sugammadex administered 42 min after 0.9 mg/kg of rocuronium. At the end of the operation, the TOF ratio was >0.9, and the patient woke normally, without signs of muscle weakness. We describe this temporary decrease in muscle response during muscle relaxation reversal as muscle relaxation rebound and hypothesize that it occurs when the dose of sugammadex is sufficient for complex formation with rocuronium in the central compartment, but insufficient for redistribution of rocuronium from peripheral to central compartments. To investigate our hypothesis, we developed and fit a simple pharmacokinetic- pharmacodynamic model of rocuronium, sugammadex, and their interaction to the patient TOF response data. Simulations using the fitted model indicate that muscle relaxation rebound can occur for doses of sugammadex in a limited critical range. Sufficiently large doses of sugammadex eliminate the possibility for muscle relaxation rebound, which does not require dissociation of the sugammadex/ rocuronium complex.

Normalization of acceleromyographic train-of-four ratio by baseline value for detecting residual neuromuscular block

This study was designed to recognize the importance of normalizing postoperative acceleromyographic train-of-four (TOF) ratio by the baseline TOF value obtained before neuromuscular block for ensuring adequate recovery of neuromuscular function. In 120 patients, TOF responses of the adductor pollicis to the ulnar nerve stimulation were monitored by acceleromyography (AMG) during anaesthesia using propofol, fentanyl and nitrous oxide. Control TOF stimuli were administered for 30 min. A TOF ratio measured at the end of control stimulation was regarded as a baseline value. Neuromuscular block was induced with vecuronium 0.1 mg kg(-1) and was allowed to recover spontaneously. Duration to a TOF ratio of 0.9 as calculated by AMG (DUR-raw 0.9) was compared with that of 0.9 as corrected by the baseline TOF ratio (i.e. 0.9 x baseline TOF ratio; DUR-real 0.9). Baseline TOF ratios ranged from 0.95 to 1.47. The average TOF ratios observed every 5 min were constant throughout control stimulation from at time zero mean (SD) [range]; 1.11 (0.09) [0.94-1.42] to at 30 min 1.13 (0.11) [0.95-1.47]. The DUR-real 0.9 was 91.0 (18.0) [51.3-131.0] min and was significantly longer than the DUR-raw 0.9 (81.2 (16.3) [41.3-123.0] min). Baseline TOF ratios measured by AMG are usually more than 1.0 and vary widely among patients. Therefore a TOF ratio of 0.9 displayed postoperatively on AMG does not always represent adequate recovery of neuromuscular function and should be normalized by baseline value to reliably detect residual paralysis.

Onset and duration of mivacurium-induced neuromuscular block in patients with Duchenne muscular dystrophy

To determine the response to mivacurium, we prospectively studied onset time and complete spontaneous recovery from mivacurium-induced neuromuscular block in patients with Duchenne muscular dystrophy (DMD). Twelve boys with DMD, age 5-14 yr, seven of them wheelchair-bound, ASA II-III, and 12 age- and sex-matched controls (ASA I) were enrolled in the study. Anaesthesia was induced with fentanyl 2-3 microg kg(-1) and propofol 3-4 mg kg(-1) titrated to effect, and maintained by continuous i.v. infusion of propofol 8-12 mg kg(-1) and remifentanil as required. The lungs were ventilated with oxygen in air. Neuromuscular transmission was assessed by acceleromyography using train-of-four (TOF) stimulation every 15 s. After baseline readings, a single dose of mivacurium 0.2 mg kg(-1) was given. The following variables were recorded: (i) lag time; (ii) onset time; (iii) peak effect; (iv) recovery of first twitch from the TOF response to 10, 25 and 90% (T(10), T(25), T(90)) relative to baseline; (v) recovery index (time between 25 and 75% recovery of first twitch); and (vi) recovery time (time between 25% recovery of first twitch and recovery of TOF ratio to 90%). For comparison between the groups the Mann-Whitney U-test was applied. There were no differences between the groups in lag time, onset time and peak effect. However, all recorded recovery indices were significantly (P<0.05) prolonged in the DMD group. The median (range) for time points T(10), T(25) and T(90) in the DMD and control group was 12.0 (8-16) vs 8.4 (5-15) min, 14.1 (9-20) vs 10.5 (7-17) min and 26.9 (15-40) vs 15.9 (12-23) min, respectively. The recovery index and recovery time were similarly prolonged in the DMD group. These results support the assumption that mivacurium-induced neuromuscular block is prolonged in patients with DMD.