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.
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Abstract |
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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
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Introduction |
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Methods |
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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 kg1 together with atropine 15 µg kg1 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 (Q1Q3) for continuous variables. The total dose of NMB agent is expressed as 95% effective dose per hour (ED95 h1).8 For the univariate analysis, comparisons were based on 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 KruskalWallis 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).
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Results |
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Discussion |
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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.
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Conclusion |
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Acknowledgments |
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References |
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