In a previous comparison of the effect of neostigmine/glycopyrrolate and sugammadex on the electromyographic activity of the diaphragm (EMGdi) by the same investigators, sugammadex was more effective than neostigmine in restoring diaphragmatic activity.1 The EMGdi and tidal volume from the first attempt to breathe spontaneously to tracheal extubation were increased after sugammadex compared with neostigmine, reflecting diaphragm-driven inspiration after sugammadex administration. The PaO2 recorded immediately after tracheal extubation was significantly higher for the sugammadex group than the neostigmine/glycopyrrolate group.
From these results, we hypothesised that the effect of neostigmine can be enhanced by the successive administration of sugammadex. When an extra group is added, as in the present study, receiving neostigmine upon the reappearance of the second twitch (T2) of the train-of-four (TOF), followed by the administration of 2 mg kg−1 sugammadex 3 min later, one would expect that neuromuscular function would be completely restored (both by neostigmine and sugammadex). If the combination of neostigmine and sugammadex were to provide the same EMGdi result as the sugammadex-only group, then we would conclude that the sugammadex effect at the neuromuscular junction predominates on the EMGdi after neostigmine followed by sugammadex. In contrast, if the combination of the two reversal agents were to show the same effect as the neostigmine group, then it would be more likely that some effect of neostigmine predominates on the EMGdi after neostigmine followed by sugammadex. In other words, neostigmine overwhelms the favourable effect of sugammadex on EMGdi. As an additional measure, we recorded the surface electromyographic (sEMG) activity of the intercostal muscles.
Our study examined three groups: the first group received neostigmine with glycopyrrolate; the second group received sugammadex and the third group received neostigmine with glycopyrrolate followed 3 min later by sugammadex. After recovery of neuromuscular blockade, the EMGdi and sEMG at the intercostal muscles were compared from the onset of spontaneous breathing to extubation of the trachea. Our investigation was performed on volunteers to ensure stable conditions, that is, in the absence of medication or surgery that could influence the observations. Moreover, postoperative pain can profoundly affect the respiratory rhythm and change in body temperature often leads to changes in the rate of breathing.
Materials and methods
Trial design, participants and randomisation
This study (ref: 2015/029) was approved by the Ethics Committee of the Onze-Lieve-Vrouw Ziekenhuis, Aalst, Belgium on 24 March 2015 and was registered with EudraCT (ref: 2015-001278-16) and ClinicalTrials.gov (ref: NCT02403063). Experiments were conducted at the Onze-Lieve-Vrouw Ziekenhuis, Aalst, Belgium, in a fully equipped intensive care facility and in the presence of board-certified anaesthesiologists for safety reasons.
This was a randomised, controlled, single-centre double-blind trial in healthy volunteers. We compared neostigmine with sugammadex and with neostigmine–sugammadex for the reversal of a moderate rocuronium-induced neuromuscular block.
In total, 18 healthy male volunteers between 18 and 40 years of age [30 (22 to 39) years; weight, 74 (56 to 89) kg; height, 179 (168 to 190) cm; all data mean (range)] were enrolled after in-depth interviews and after providing written informed consent. Individuals with BMI more than 26 kg m−2, history of smoking or nose/sinus surgery, medication known to interfere with neuromuscular blocking agents, family or personal history of problems related to anaesthesia, reflux oesophagitis, or current upper airway infection were excluded. Participants were randomised into one of three groups after inclusion in the study: the first group received 50 μg kg−1 neostigmine with 10 μg kg−1 glycopyrrolate; the second group received 2 mg kg−1 sugammadex; the third group received 50 μg kg−1 neostigmine with 10 μg kg−1 glycopyrrolate followed by 2 mg kg−1 sugammadex 3 min later. To maintain blinding, we offered two syringes to the investigator (GC): one with the active drug (neostigmine/glycopyrrolate or sugammadex) at the moment of T2 return at the TOF, and one with sugammadex or 0.9% NaCl 3 min later depending on the group into which the volunteer had been randomly assigned. All syringes were covered with tape to conceal the volume and colour of the contents.
The methodology of this study was as previously described.1Figure 1 shows a flow chart of the study protocol. Noninvasive blood pressure was recorded every 5 min, and the heart rate, ECG, end-tidal carbon dioxide concentration and arterial oxygen saturation (SpO2) were continuously recorded. An intravenous cannula was inserted into the antecubital vein, and lactated Ringer's solution was infused. An arterial cannula was inserted into the radial artery after the induction of anaesthesia. Body temperature was maintained by a forced warm air blanket. An auxiliary sEMG (Dipha16, Inbiolab BV, DEMCON group, Groningen, The Netherlands) was recorded at the intercostal muscles (midclavicular line at the second intercostal space) using surface electrodes. The degree of neuromuscular blockade was continuously measured using the accelerometry of the adductor pollicis muscle via ulnar nerve stimulation (TOF-watch SX; MIPM Mammendorfer Institut für Physik und Medizin GmbH, Munich, Germany). Anaesthesia was induced via a propofol intravenous target-controlled infusion and the addition of remifentanil. Thereafter, the propofol infusion rate, the remifentanil infusion rate or both was decreased when the mean blood pressure decreased to more than 10% of baseline. Manually assisted ventilation with an air/oxygen mixture of 40% oxygen began as soon as the volunteers became apnoeic. TOF monitoring started after the induction of anaesthesia (before rocuronium administration) and continued until awakening. TOF-Watch SX calibration was performed as previously described.1 We inserted a 16-Fr nasogastric catheter, which allowed EMGdi registration [neurally adjusted ventilator assist, (NAVA); catheter, Maquet, Solna, Sweden]. The NAVA catheter was advanced to the predicted correct depth as defined by the manufacturer, the nasal-ear-xiphoid distance × 0.9 + 18 cm; the position of the NAVA catheter was confirmed using the ‘Edi catheter positioning’ tool. After baseline TOF measurements, 0.6 mg kg−1 rocuronium was injected. The TOF ratio was monitored, recorded and later analysed using TOFMON software (Organon Laboratories Ltd, Dublin, Ireland). Normalised acceleromyographic TOF ratios were calculated by dividing the TOF ratio by the study participant's baseline value. Endotracheal intubation and mechanical ventilation were performed after the T1 of the TOF response disappeared. EMGdi, obtained from the NAVA catheter, airway pressure and flow were acquired at 100 Hz from the ventilator via an interface connected to a computer using commercially available software (Maquet Critical Care, Solna, Sweden).
Participants were ventilated with an inspired oxygen fraction of 30%, with an end-tidal carbon dioxide target of 4.66 to 5.33 kPa and a positive end-expiratory pressure of 5 cmH2O. Spontaneous recovery of the neuromuscular block was allowed to progress until the reappearance of T2. The volunteers then received either 50 μg kg−1 neostigmine + 10 μg kg−1 glycopyrrolate (using the commercially available 5 : 1 coformulation) or 2 mg kg−1 sugammadex or 50 μg kg−1 neostigmine + 10 μg kg−1 glycopyrrolate followed by the administration of 2 mg kg−1 sugammadex 3 min later. At that time we discontinued the administration of remifentanil. At least 5 min after the first reversal drug administration and upon full recovery of neuromuscular block, as defined by three measurements of TOF at least 0.9, the propofol infusion was stopped and the minute volume was reduced by 50% with end-tidal carbon dioxide targets between 6 and 7.33 kPa. When spontaneous breathing effort was observed, either via the NAVA catheter or the ventilator, the participant's ventilation mode was switched to continuous positive airway pressure with 5 cmH2O of positive end-expiratory pressure. NAVA catheter positioning was reconfirmed using the ‘Edi catheter positioning’ tool as soon as a signal was received. The volunteers’ tracheas were extubated as soon as they were fully awake and able to follow commands.
We computed the following variables: the time from the administration of rocuronium to first administration of reversal agent, the time from first reversal to a normalised TOF ratio of 0.9, the normalised TOF ratio at sugammadex injection (as the second reversal in the neostigmine–sugammadex group), the time from a normalised TOF ratio of 0.9 to the first spontaneous breathing attempt, the normalised TOF ratio at first spontaneous breathing attempt, the time from the first spontaneous breathing attempt to extubation, and the normalised TOF ratio immediately before tracheal extubation. We recorded the baseline SpO2, the SpO2 during anaesthesia, the PaO2 between the onset of spontaneous breathing and extubation of the trachea (during quiet breathing) and the SpO2 postanaesthesia.
EMGdi, airway pressure and flow were recorded continuously throughout the anaesthetic procedure until the moment of tracheal extubation. The flow, pressure and EMGdi curves were mapped on a computer for analysis and only the EMGdi values recorded during quiet breathing were retained. EMGdi values associated with coughing were not considered for analysis. A cough was defined as peak positive pressure combined with simultaneous peak expiratory flow. The subsequent inspiratory flow was considered an abnormal movement, and this inspiration was also not retained for analysis. Breaths with a tidal volume of less than 100 ml were not retained either. The time from the start to the end of inspiratory flow was matched with the corresponding EMGdi recording, and the maximal EMGdi value was selected for that inspiration (peak EMGdi). Each tidal volume was recorded with its corresponding peak EMGdi. The sEMG of the intercostal muscles was recorded continuously throughout the procedure and synchronised with the EMGdi, airway pressure and flow registration. The peak sEMG of the intercostal muscles that corresponded with the peak EMGdi was identified for every inspiration that was retained for analysis.
We recorded the overall peak EMGdi and the peak EMGdi of all breaths with EMGdi more than 0.5 μV and those with EMGdi at least 1 μV from the first spontaneous breathing attempt to extubation for all three groups. We recorded the number of breaths with EMGdi at least 1 μV for all three groups. We also recorded the overall peak sEMG of the intercostal muscles for all three groups. Because of the low voltage of the sEMG signal compared with the EMGdi, we did not separately calculate the peak sEMG of the intercostal muscles of breaths with sEMG more than 0.5 μV or at least 1 μV. We recorded the number of breaths with sEMG at least 1 μV for all three groups.
Because this was the first study of this nature, we had no data on which to base a sample size calculation. Instead, we chose to use the same number of volunteers as in a previous volunteer study that had proved satisfactory.1
The data are expressed as median (95% confidence interval) unless otherwise stated. Comparisons were performed using one-way analysis of variance (nonparametric Kruskal–Wallis test), followed by Dunn's multiple comparisons posttest, when the P value was less than 0.05. Categorical data are expressed as numbers (%). To assess potential differences between groups for categorical variables, a contingency table was generated and Fisher's exact test was performed. All statistical tests were two tailed, and a P value less than 0.05 was considered significant. Statistical analyses were performed using GraphPad Software (GraphPad, La Jolla, California, USA).
The primary objective of this study was to evaluate the EMGdi and sEMG at the intercostal muscles during recovery enhanced by 50 μg kg−1 neostigmine, 2 mg kg−1 sugammadex or 50 μg kg−1 neostigmine followed by the administration of 2 mg kg−1 sugammadex 3 min later. The secondary objectives were to evaluate the tidal volume of the breaths recorded between the onset of spontaneous breathing and the extubation of the trachea, PaO2 between the onset of spontaneous breathing and the extubation of the trachea during quiet breathing and SpO2 during and after anaesthesia.
One volunteer withdrew consent the morning of the study before receiving study medication and was replaced by a reserve. In total, 18 individuals completed the study without untoward reactions. The EMGdi nasogastric catheter positioning was straightforward, and the correct position was achieved for every individual. There were no adverse events related to the study medication. No additional oxygen was supplied and no airway manoeuvres were necessary after extubation of the trachea. After the EMGdi data were reviewed, 1037 breaths were identified. In total, 593 breaths were retained for analysis: 212 in the neostigmine group, 203 in the sugammadex group and 178 in the combined drugs group. The remaining 444 breaths were excluded from further statistical analysis because of a tidal volume less than 100 ml or because they were associated with coughing.
Table 1 shows neuromuscular block recovery and respiratory variables following the injection of neostigmine/glycopyrrolate (n = 6) or sugammadex (n = 6) at T2, followed by saline 3 min later or injection of neostigmine/glycopyrrolate (n = 6) at T2, followed by sugammadex 3 min later. The normalised TOF ratio at sugammadex injection (the second reversal) in the neostigmine–sugammadex group was 74.5 (49 to 104) %.
Table 2 shows the peak EMGdi from the first spontaneous breathing attempt to tracheal extubation and the peak sEMG of the intercostal muscles from the first spontaneous breathing attempt to tracheal extubation. Figure 2 shows the peak EMGdi of all breaths: EMGdi was increased after sugammadex compared with neostigmine or neostigmine followed by sugammadex. Breaths with associated EMGdi values not exceeding 0.5 μV are highly unlikely to be breaths in which the majority of the tidal volume is generated by the diaphragm. Our data demonstrate that the peak EMGdi of breaths with EMGdi more than 0.5 μV was increased after sugammadex compared with neostigmine or neostigmine followed by sugammadex. The neostigmine-associated decrease in EMGdi did not alter the TOF ratio (Table 1).
Figure 3 shows the peak sEMG of the intercostal muscles of all of the breaths from the first spontaneous breathing attempt to tracheal extubation. The peak sEMG of the intercostal muscles was higher in study participants receiving sugammadex alone or neostigmine followed by sugammadex than in study participants receiving only neostigmine. The decrease in sEMG in the neostigmine group was not associated with alterations in the TOF ratio compared with the two other groups (Table 1).
The median tidal volume of all of the breaths considered suitable for analysis in the neostigmine group was 384 (349 to 386) ml, compared with 327 (346 to 411) ml in the sugammadex group and 262 (294 to 371) ml in the neostigmine–sugammadex group (P = 0.0002, with only the tidal volume in the neostigmine group differing from the tidal volume in the neostigmine-sugammadex group). The PaO2 between the onset of spontaneous breathing and the extubation of the trachea during quiet breathing for the neostigmine group was 15 (10 to 22.9) kPa vs. 16.9 (10.3 to 24.8) kPa for the sugammadex group and 12.6 (9.1 to 17.2) kPa for the neostigmine–sugammadex group (P = 0.35). The SpO2 did not differ among the three groups at any time (Table 1).
In this randomised double-blind trial in healthy volunteers, we compared neostigmine with sugammadex and neostigmine–sugammadex in the reversal of a moderate rocuronium-induced neuromuscular block. The most important finding of this study was that the EMGdi increased after sugammadex reversal of the rocuronium block compared with neostigmine or neostigmine followed by sugammadex during weaning from the ventilator. This finding reflects diaphragm-driven inspiration after sugammadex administration. Giving sugammadex after neostigmine resulted in a condition that arises when neostigmine is given after the full recovery of the neuromuscular block, where a neostigmine-induced depolarising neuromuscular weakness is a consequence. In contrast, the peak sEMG of the intercostal muscles was higher in study participants receiving sugammadex alone or neostigmine followed by sugammadex than in study participants receiving only neostigmine. The different decreases in EMGdi and intercostal sEMG during weaning did not affect the adductor pollicis muscle TOF ratios. The median tidal volume of all of the analysed breaths was different only between the neostigmine group and the neostigmine–sugammadex group, with the latter group experiencing the smallest tidal volume. The PaO2 between the onset of spontaneous breathing and the extubation of the trachea during quiet breathing did not differ among groups, nor did the SpO2 during and after anaesthesia.
This study confirms findings from our previous work that EMGdi during weaning from the ventilator is increased after sugammadex compared with neostigmine.1 Moreover, our group showed that rats that received neostigmine as a reversal agent displayed a smaller relative contribution of diaphragm movement to total change in lung volume than rats that received sugammadex or saline.2 It is well known that reductions in diaphragm activity are associated with the development of atelectasis postoperatively.3 It is speculated that sugammadex might simply free more diaphragmatic acetylcholine receptors than indirect-acting neostigmine.4 This supposition was reinforced in this study given the observation of enhanced diaphragm-driven inspirations during the initial period following the recovery of the TOF to 0.9. However, a sugammadex effect on neuromuscular transmission at the muscle level cannot completely explain why the EMGdi during weaning after sugammadex alone in the present study was greater than that after sugammadex following earlier treatment with neostigmine. The measured EMGdi reflects the electrical activity of muscle cells, which is determined not only by effective neuromuscular transmission but also the total activity in the phrenic nerve. Eikermann et al.5 demonstrated that neostigmine alone (without prior treatment with a neuromuscular blocking agent) decreased EMGdi. This result might be explained by a possible effect on neuromuscular transmission at the muscle level or a neostigmine-induced decrease in total nerve activity. Neostigmine abolished phrenic nerve activity in cats.6 Consequently, a neostigmine-induced decrease in total phrenic nerve activity might explain why the EMGdi during weaning from the ventilator was decreased after neostigmine followed by sugammadex compared with sugammadex alone. These studies5,6 demonstrated neostigmine-induced weakness in study participants who had no block when neostigmine was given. There is no real evidence of neostigmine-induced weakness in participants who receive the drug when moderate blockade (in the present study reversal at two visible twitches) was present.
Based on our data, we speculate that adding sugammadex after neostigmine creates a situation in which neostigmine may induce a weakness. In the present study, sugammadex removed the rocuronium-induced neuromuscular blockade; thus, neostigmine behaves as though no rocuronium had been administered. In that case, the diaphragm is vulnerable to an overabundance of acetylcholine at the neuromuscular junction, resulting in decreases in the diaphragm electromyogram. Neostigmine administered after the full recovery of the neuromuscular block, with a neostigmine-induced depolarising neuromuscular weakness as a consequence, has been extensively described in animals as well as in humans, placing participants at risk for impaired diaphragm muscle function5 and increased upper airway collapsibility.7
Because respiration clearly depends on the activity of both the diaphragm and the thoracic inspiratory muscles, we studied the diaphragm and intercostal muscle EMG, which has not been previously reported simultaneously in this setting. Our results clearly showed that the peak sEMG of the intercostal muscles was higher in participants who received sugammadex alone and in those who received neostigmine followed by sugammadex than in those receiving only neostigmine. This finding might be explained by the different sensitivities of various muscle groups to the effect of neuromuscular blocking agents.8 In particular, the diaphragm is more resistant to neuromuscular blockade than, for example, the intercostal muscles where recovery may well lag behind that of the diaphragm, and they may benefit from the additional sugammadex given in our third group, resulting in an increased intercostal sEMG compared with the group given only neostigmine. Alternatively, we hypothesise that neostigmine causes a clearly different pattern of depressed phrenic and intercostal activities. The selectivity of drug-induced phrenic nerve depression has been demonstrated in the past. Eikermann et al.9 reported phrenic nerve depression combined with genioglossus respiratory activity stimulation after administering pentobarbital in rats. In our study, the intercostal muscles have a different sensibility to the neostigmine–sugammadex combination than has the diaphragm and it seems as if the intercostal effect of sugammadex in addition to neostigmine was additive (Table 2).
The present investigation has limitations. First, one could argue that combining sugammadex and neostigmine/glycopyrrolate poses the risk of an interaction between the cyclodextrin sugammadex and the two agents, thereby reducing the effective concentrations of either neostigmine or glycopyrrolate. However, the affinity of sugammadex for neostigmine and glycopyrrolate is very low.10 Therefore, a potential interaction is unlikely. Second, the clinical relevance of this study is limited: although used as rescue treatment,11,12 there is no evidence to support the administration of sugammadex within 3 min following neostigmine. Third, the quality of a transcutaneous EMG signal may be inferior to the EMG signal received via a transoesophageal recorder as observed in the lower EMG amplitudes (μV) in our intercostal sEMG data. Thus, it might be difficult to draw conclusions from data generated by these different measurement techniques. However, we feel that there was no methodological alternative because the NAVA catheter cannot measure the EMG of the intercostal muscles. Moreover, we deliberately opted for EMGdi registration with the NAVA catheter (instead of a transcutaneous method) because when the EMGdi is acquired through the oesophagus, the quality of the signal is not subject to artefact from expiratory muscles or negative effects from subcutaneous layers.13 Moreover, the oesophageal recording of diaphragm action potential exhibits higher amplitudes than surface recordings.14 Fourth, the greater tidal volume and the higher PaO2 during weaning from the ventilator in the participants receiving sugammadex vs. neostigmine in our previous study1 was not reproduced in the present study. Finally, although participants in all of the groups were able to generate values of 5 μV or higher, the median values were approximately 1 μV or less. In other words, the primary outcome (EMG) did not actually test maximum diaphragmatic function because the majority of the EMG data collected between the onset of spontaneous breathing and the extubation of the trachea occurred during ‘quiet breathing’, which does not require much neuromuscular power.
In summary, prior administration of neostigmine decreased the effect of sugammadex on the diaphragm compared with the effect without neostigmine priming. Regarding the intercostal muscles no similar interaction occurred.
Acknowledgements related to this article
Assistance with the study: the authors thank Anton H Bom (Livingston, Scotland) for thoughtful feedback. Kristel Van Varenbergh and Benny Desmedt provided practical assistance during the study and provided care for the study volunteers. Annick Peremans was the clinical monitor of this study. The authors thank Leo A van Eykern (Groningen, The Netherlands) for his assistance in analysing the sEMG data.
Financial support and sponsorship: this work was supported by sources of the Department of Anaesthesiology and Critical Care Medicine, Aalst, Belgium. NAVA catheters were kindly provided by Maquet Getinge Group.
Conflicts of interest: GC received research grants and lecture fees from MSD and previously performed funded research on sugammadex. GC has served on the advisory board for MSD Belgium. TS received research grants and lecture fees from MSD. PGJ received investigator-initiated research funding from the Maquet Getinge Group. The other authors declare no conflicts of interests. The authors have no financial relationships with any organisation or company that may have an interest in the submitted work. MSD had no role in this study whatsoever.
Presentation: the findings of this study were partially presented at the 2016 Euroanesthesia Congress, London, UK.
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