Postoperative residual neuromuscular block: a survey of management

C. Baillard*, C. Clec'h, J. Catineau, F. Salhi, G. Gehan, M. Cupa and C. M. Samama

Département d'Anesthésie-Réanimation, EA 3409, Hôpital Avicenne, APHP, 93009 Bobigny Cedex, France

* Corresponding author. E-mail: christophe.baillard{at}avc.ap-hop-paris.fr

Accepted for publication August 17, 2005.


    Abstract
 Top
 Abstract
 Introduction
 Methods
 Results
 Discussion
 Conclusion
 References
 
Background. To avoid postoperative residual neuromuscular block there is a need for a change in clinician's attitude towards monitoring and reversal. This study aims to evaluate changes of perioperative neuromuscular block management during the last decade in our institution and to quantify the incidence of postoperative residual neuromuscular block.

Methods. Patients receiving intermediate-acting neuromuscular blocking agents for scheduled surgical procedures during 3-month periods in 1995 (n=435), 2000 (n=130), 2002 (n=101), and in 2004 (n=218) were prospectively and successively enrolled in our study. The management of neuromuscular block in the operating room and the adequacy of the recovery were at the discretion of the anaesthesiologist. An attempt was made between each study period to promote a change in the management of neuromuscular block. In the post-anaesthesia care unit, train-of-four (TOF) stimulations were used to assess the presence of a residual neuromuscular block.

Results. Between 1995 and 2004 quantitative measurement and reversal of neuromuscular block in the operating room increased from 2 to 60% and from 6 to 42%, respectively (P<0.001). During the same time, the incidence of residual neuromuscular block defined as a TOF ratio less than 0.9 decreased from 62 to 3% (P<0.001). Use of objective neuromuscular monitoring and/or anticholinesterase drugs was less likely in patients with an inadequate recovery (P<0.001).

Conclusions. During the last decade the incidence of residual neuromuscular block strongly decreased in our institution. It confirms the positive impact of neuromuscular monitoring and reversal of neuromuscular block in routine anaesthetic practice.

Keywords: antagonists neuromuscular block, neostigmine ; neuromuscular block, monitoring ; neuromuscular function


    Introduction
 Top
 Abstract
 Introduction
 Methods
 Results
 Discussion
 Conclusion
 References
 
During the past 25 yr, numerous publications have confirmed the clinical importance of postoperative residual neuromuscular block.1 The idea that intermediate-acting neuromuscular blocking (NMB) agents have resolved the problem of postoperative residual neuromuscular block seems to be inaccurate.2 Ten years ago, we found that among 435 extubated patients given vecuronium during anaesthesia, 145 (33%) had a train-of-four (TOF) ratio below 0.7 in the postanaesthesia care unit (PACU).3 Several editorials have focused on the need for a change in the attitude towards monitoring and reversal of neuromuscular block, one author even stating that: ‘if you do not monitor or antagonize neuromuscular blockade ... an unacceptably high proportion of patients will have clinically significant residual block’.4 Unfortunately, these guidelines are not always followed.5 Debaene and colleagues still found an alarmingly high incidence of postoperative residual neuromuscular block after a single dose of intermediate NMB agents when neuromuscular monitoring and/or reversal were not used.6 It is now established that reversal of NMB agents reduces severe morbidity and mortality.7 Hypothesizing a change in our practice since 1995, residual neuromuscular block as well as the use of perioperative monitoring and reversal of NMB agents were again prospectively and successively evaluated in 2000, 2002, and 2004. The present study aims to compare these periods in terms of management of NMB agents in the operating room and to look for a relationship with the incidence of postoperative residual neuromuscular block.


    Methods
 Top
 Abstract
 Introduction
 Methods
 Results
 Discussion
 Conclusion
 References
 
Between 1995 and 2004, 884 patients receiving an intermediate-acting NMB agent during general anaesthesia for a scheduled surgical procedure (orthopaedic, abdominal, thoracic, ENT, or vascular surgery) were prospectively evaluated in the PACU. Patients were successively enrolled in the study during 3-month periods in 1995 (n=435),3 2000 (n=130), 2002 (n=101), and in 2004 (n=218). No attempt was made to influence the anaesthetic technique in any way during each study period. However, anaesthesiologists and anaesthesiologist nurses received information about the incidence of postoperative residual neuromuscular block as well as the use of monitoring and reversal at the end of each study period to promote a change in the management of NMB agents in the operating room. In addition, neuromuscular transmission monitoring devices became available in each operating room after 1995.

The choice of drugs used for pre-medication and anaesthesia was at the discretion of the anaesthesiologist. Most patients were pre-medicated with hydroxyzine 100 mg orally. After arriving in the operating room, patients were placed on the operating table and kept warm with a blanket. Induction was performed with propofol or etomidate and fentanyl (1995) or sufentanil. Anaesthesia was maintained with isoflurane (1995) or desflurane in a nitrous oxide/oxygen (60/40%) mixture. The management of neuromuscular block in the operating room, the adequacy of the recovery, and the decision to extubate the trachea before arrival in the recovery room were left at the discretion of the anaesthesiologist.

Immediately after arrival in the PACU, a pair of electrodes was applied over the ulnar nerve at the wrist. The evoked response at the thumb was measured by TOF-Guard® or TOF-Watch® acceleromyographs (Organon-Teknika, Puteaux, France). The probe was positioned on the distal ventral part of the thumb. The other fingertips were tightly fixed with tape. The ulnar nerve was stimulated with TOF stimulation (four pulses 0.2 ms in duration, at a frequency of 2 Hz, 2 s in duration). The current intensity was 30 mA. Postoperative residual neuromuscular block was defined as a TOF ratio less than 0.9. Neostigmine 40 µg kg–1 together with atropine 15 µg kg–1 were given to antagonize residual neuromuscular block when necessary.

Exclusion criteria were neuromuscular diseases, preoperative medication that may interfere with neuromuscular transmission, and severe kidney or liver disease. The observational study was prospective, open-labelled, non-randomized. Acceleromyographic monitoring in the PACU was a routine clinical practice at our institution. This protocol was considered as a quality assurance project and part of routine clinical practice. Therefore, no informed consent was required from the patients as confirmed by the local IRB.

Statistical analysis
Results are expressed as numerical values and percentages for categorical data and as medians and quartiles (Q1–Q3) for continuous variables. The total dose of NMB agent is expressed as 95% effective dose per hour (ED95 h–1).8 For the univariate analysis, comparisons were based on {chi}2-test or Fisher's exact test for categorical data and on Student's t-test, one-way analysis of variance, Wilcoxon's test or Kruskal–Wallis test for continuous data when appropriate.

The relationship between postoperative residual neuromuscular block and potential explanatory variables was computed using a logistic regression model. Variables thought to have clinical importance, and those with P<0.1 in the univariate analysis were included into the model to determine those that were independently associated with postoperative residual neuromuscular block. A second logistic regression model was used to determine independent predictors of absence of reversal of NMB agents. All tests were two-tailed and P<0.05 was considered significant. Statistical analysis was performed with the SAS 8.0 software package (SAS Institute, Cary, NC).


    Results
 Top
 Abstract
 Introduction
 Methods
 Results
 Discussion
 Conclusion
 References
 
Patients
A total of 884 patients were evaluated. 559 patients underwent abdominal procedures and 325 non-abdominal procedures. There was no significant difference in ASA score or in the type of surgery between the four study periods. Age, body weight, and duration of surgery increased over time (Table 1).


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Table 1 General characteristics of patients. Mean (SD) or quartiles [Q1–Q3] or absolute number. NS, not significant

 
NMB agents' management
NMB agents' monitoring and reversal regularly increased between 1995 and 2004 (Table 2). Concurrently, there was a dramatic decrease in the proportion of patients with postoperative residual neuromuscular block (Fig. 1). The main NMB agent used in 1995 was vecuronium whereas in 2004 it was atracurium. The relaxant dose differed significantly between the patients with (n=241) or without neuromuscular monitoring (n=643): 1.24 (±0.58) vs 1.48 (±0.95) ED95 h–1, P=0.005.


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Table 2 Perioperative NMB agents' management. Quartiles [Q1–Q3] or absolute number (%). ED95, 95% effective dose

 


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Fig 1 Evolution of intraoperative NMB agents' management and postoperative residual neuromuscular block defined as a TOF ratio less than 0.9.

 
Determinants of postoperative residual neuromuscular block
In the univariate analysis, patients with an inadequate recovery (TOF ratio <0.9) received a higher dose of muscle relaxants and had neuromuscular function less likely monitored and/or NMB agents reversed in the operating room, P<0.001 (Table 3). The duration of surgery was also shorter in these patients, P<0.001. The three independent determinants of postoperative residual neuromuscular block as evaluated by logistic regression were: absence of neuromuscular monitoring and reversal of NMB agents as well as a shorter duration of surgery (Table 4).


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Table 3 Determinants of postoperative neuromuscular block, univariate analysis.

 

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Table 4 Determinants of postoperative neuromuscular block, logistic regression. NMB, neuromuscular blocking. OR, odds ratio. CI, confidence interval

 
Determinants of absence of reversal of NMB agents
In the univariate analysis, variables associated with the use of reversal of NMB agents were: duration of surgery, neuromuscular monitoring, and time from last injection of NMB agents to TOF recording in PACU, P<0.01 (Table 5). Logistic regression model found neuromuscular monitoring and time from last injection of NMB agents to TOF recording in PACU were the only two independent predictors of the use of reversal of NMB agents (Table 6).


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Table 5 Determinants of absence of reversal of NMB agents, univariate analysis. Means (SD) or quartiles [Q1–Q3] or absolute number and %. ED95, 95% effective dose

 

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Table 6 Determinants of absence of reversal of NMB agents, logistic regression. OR, odds ratio. CI, confidence interval

 

    Discussion
 Top
 Abstract
 Introduction
 Methods
 Results
 Discussion
 Conclusion
 References
 
This study shows that between 1995 and 2004 both the management of NMB agents in the operating room and the incidence of postoperative residual neuromuscular block have substantially evolved in our institution. Usual risk factors of residual neuromuscular block such as the lack of monitoring and reversal of NMB agents in the operating room have been identified.

Observational studies are useful in shedding light on the effectiveness of many aspects of health care.9 They also provide information on actual anaesthetic practice. Such studies have evidenced a high incidence of postoperative residual neuromuscular block13 6 and have advocated monitoring and reversal of neuromuscular block.4 10 Moreover, because practice guidelines are not always followed, postoperative residual neuromuscular block is still an existing concern in the PACU.6 The ‘local’ incidence of postoperative residual neuromuscular block within an institution is frequently unknown and confounding factors during anaesthesia recovery may result in an underestimation of the morbidity related to postoperative residual neuromuscular block.11 In addition, Arbous and colleagues have recently demonstrated the enormous safety aspect of reversal and monitoring on the postoperative morbidity and mortality.7

In order to improve our clinical practice, neuromuscular transmission monitoring devices became available in our operating room after the alarming results of our study performed in 1995.3 However, it should be noticed that despite a substantial improvement since 1995, 40% of patients are still not monitored with an objective device when administered NMB agents during surgery. Neuromuscular transmission monitoring devices allow for accurate titration, a more rational use of the NMB agents and thus a reduction in the incidence of postoperative residual neuromuscular block.12 Our study confirms that when the NMB agents are monitored in the operating room, the dose of NMB agents and the incidence of residual neuromuscular block decrease. In addition, reversal of NMB agents was best used when combined with neuromuscular monitoring.

Previous studies have clearly shown that residual neuromuscular block depends on whether anticholinesterase drugs are administered or not.13 As a rule, in this study, neuromuscular function in PACU was more frequently adequate in patients receiving anticholinesterase drugs. It is likely that anticholinesterase drugs were administered preferentially to patients who had a greater degree of paralysis because the time from last NMB agent injection was shorter in these patients.

We have examined something close to routine clinical practice. The anaesthesiologist was free to select the NMB agent, the dose, and whether to use or not neuromuscular monitoring or anticholinesterase drugs. The clinical criteria for evaluating recovery of neuromuscular block were not standardized and were at the discretion of the anaesthesiologist. The periods studied were different regarding the muscle relaxants used as well as intra-operative halogenated gases (isoflurane vs desflurane). However, muscle relaxants used in the study were intermediate-acting agents. In addition, the design of this study did not allow us to take into account other factors that may have changed during the period studied and that could have influenced our results. Nevertheless, this observational study was a practical mean to obtain relevant information, to assess our clinical practice and to contribute to improvement of care.


    Conclusion
 Top
 Abstract
 Introduction
 Methods
 Results
 Discussion
 Conclusion
 References
 
During the last decade the incidence of residual neuromuscular block after intermediate-acting NMB agents' use strongly decreased in our institution. This study confirms the interest of changing our attitude towards monitoring and reversal of NMB agents in routine anaesthetic practice.10


    Acknowledgments
 
Work performed in the Anaesthesiology Department, Avicenne Hospital, Paris, France.


    References
 Top
 Abstract
 Introduction
 Methods
 Results
 Discussion
 Conclusion
 References
 
1 Viby-Mogensen J, Jorgensen BC, Ordin M. Residual neuromuscular blockade in the recovery room. Anesthesiology 1979; 50: 539–41[ISI][Medline]

2 Fawcett WJ, Dash A, Francis GA, Liban JB, Cashman JN. Recovery from neuromuscular blockade: residual curarisation following atracurium or vecuronium by bolus dosing or infusions. Acta Anaesthesiol Scand 1995; 39: 288–93[ISI][Medline]

3 Baillard C, Gehan G, Reboul-Marty J, Larmignat P, Samama CM, Cupa M. Residual curarisation in the recovery room after vecuronium. Br J Anaesthesia 2000; 84: 394–5[Abstract]

4 Viby-Mogenson J. Postoperative residual curarisation and evidence-based anaesthesia. Br J Anaesthesia 2000; 84: 301–3[Free Full Text]

5 Osmer C, Vogele C, Zickmann B, et al. Comparative use of muscle relaxants and their reversal in three European countries: a survey in France, Germany and Great Britain. Eur J Anaesthesiol 1996; 13: 389–99[CrossRef][ISI][Medline]

6 Debaene B, Plaud B, Dilly MP, et al. Residual paralysis in the PACU after a single intubating dose of nondepolarizing muscle relaxant with an intermediate duration of action. Anesthesiology 2003; 98: 1042–8[CrossRef][ISI][Medline]

7 Arbous MS, Meursing AE, van Kleef JW, et al. Impact of anesthesia management characteristics on severe morbidity and mortality. Anesthesiology 2005; 102: 257–68[CrossRef][ISI][Medline]

8 Debaene B, Beaussier M, Meistelman C, Donati F, Lienhart A. Monitoring the onset of neuromuscular block at the orbicularis oculi can predict good intubating conditions during atracurium-induced neuromuscular block. Anesth Analg 1995; 80: 360–3[Abstract]

9 Black N. Why we need observational studies to evaluate the effectiveness of health care. Br Med J 1996; 312: 1215–18[Free Full Text]

10 Eriksson LI. Evidence-based practice and neuromuscular monitoring. Anesthesiology 2003; 98: 1037–9[ISI][Medline]

11 Berg H, Viby-Mogensen J, Roed J, et al. Residual neuromuscular block is a risk factor for postoperative pulmonary complications. A prospective, randomised, and blinded study of postoperative pulmonary complications after atracurium, vecuronium and pancuronium. Acta Anaesthesiol Scand 1997; 41: 1095–103[ISI][Medline]

12 Gatke MR, Viby-Mogensen J, Rosenstock C, Jensen FS, Skovgaard LT. Postoperative muscle paralysis after rocuronium: less residual block when acceleromyography is used. Acta Anaesthesiol Scand 2002; 46: 207–13[CrossRef][ISI][Medline]

13 Bevan DR, Donati F, Kopman AF. Reversal of neuromuscular blockade. Anesthesiology 1992; 77: 785–805[ISI][Medline]





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