Abstract
Residual neuromuscular block (NMB) may persist in the post-anaesthesia care unit (PACU). 1 Studies in our department found that our incidence of postoperative residual NMB was approximately 40% in 2006 and 14% in 2012.2,3 We would like to report the results of a follow-up study of residual NMB in our department in 2018. The primary objective of this study was to evaluate the incidence of residual NMB, defined by a train-of-four ratio (TOFR) < 0.9 on PACU arrival. This observational study involved patients undergoing different types of elective surgery that required general anaesthesia with neuromuscular blocking agents (NMBAs). The anaesthetic technique and the management of NMB in the operating room were conducted at the discretion of the attending anaesthetist and were performed in accordance with our standard clinical practice and with reference to published practice guidelines for the intraoperative management of NMB. 4 After signed informed consent, 587 patients were prospectively and successively enrolled in our study. The study was approved by the Ethics Committee of the Onze-Lieve-Vrouw Ziekenhuis, Aalst, Belgium (Approval 2017/077, Chairperson Dr A Leloup) on 6 October 2017 and is registered at ClinicalTrials.gov (ID: NCT03665805).
On arrival in the PACU, a nurse trained in TOFR monitoring (TOFscan™, iDMed, Marseille, France) recorded the acceleromyographic responses of the adductor pollicis muscle (as the TOFR) on TOF stimulation of the ulnar nerve. The stimulus current was set at 30 mA for the purpose of tolerance. Two consecutive TOF measurements (separated by 15 seconds) were obtained, and the average of the two values was registered. We recorded whether neuromuscular transmission (NMT) monitoring was used before extubation of the trachea in the operating room and whether extubation in the operating room was preceded by pharmacological reversal with either neostigmine or sugammadex. Patients’ characteristics and perioperative data, as well as the management of NMB, and the incidence of residual NMB were retrieved from the 2012 results, 3 and the same variables were collected for the 2018 study. We compared the variables between the two periods using Mann–Whitney tests for continuous variables and chi-square tests for categorical variables. In addition, we divided the 2018 TOFR results into six subgroups: a) patients not monitored with NMT and not reversed with reversal agents (n = 112); b) patients who had no NMT monitoring but had reversal with neostigmine (n = 33); c) patients monitored but not reversed (n = 181); d) patients monitored and reversed with neostigmine (n = 181); e) patients monitored and reversed with sugammadex (n = 75); and f) patients monitored and reversed with both neostigmine and sugammadex (n = 5). We then calculated how many patients in each subgroup had a TOFR between 0.7 and 0.9 and how many had a TOFR < 0.7.
Table 1 shows the characteristics of the patients and their intraoperative NMB monitoring, reversal management and the incidence of residual NMB for the 2012 and the 2018 studies. Both the use of neuromuscular monitoring and the proportion of patients who had NMB reversed pharmacologically increased between 2012 and 2018. Surprisingly, however, there was no significant decrease in the proportion of patients with residual NMB. The incidence of a TOFR < 0.9 remained at 14% for both periods. Moreover, despite literature advocating NMT monitoring and the reversal of NMB to reduce postoperative residual NMB,1,5 25% of our patients receiving NMBAs were still not monitored with a quantitative device. The incidence of TOFR between 0.7 and 0.9 and of a TOFR < 0.7 in the six subgroups were: (a) 12%, 4%; (b) 15%, 0%; (c) 11%, 2%; (d) 12%, 2%; (e) 11%, 0%; and (f) 20%, 0%. This indicates a considerable number of patients had a TOFR < 0.9 and even <0.7 in the PACU, even when monitored quantitatively. However, in our study no patients who received sugammadex had a TOFR < 0.7; some had a TOFR between 0.7 and 0.9 (groups e and f). As these patients had NMB monitoring intraoperatively, the lack of appropriate dosing of sugammadex or the lack of checking the TOFR before the transfer to the PACU could be the only explanations for the residual NMB.
General characteristics of patients, intraoperative neuromuscular blockade monitoring and reversal management and the incidence of residual neuromuscular blockade for the two periods (2012 and 2018).
Data are median (range) or absolute number (%).
NMB: neuromuscular block; NMT: neuromuscular transmission; NMBAs: neuromuscular blocking agents; TOFR: train-of-four ratio; PACU: postanaesthesia care unit.
aData from Cammu GV, Smet V, De Jongh K, et al. Anaesth Intensive Care 2012; 40: 999–1006.
bFive patients received neostigmine as well as sugammadex for reversal.
The failure to recognise residual NMB can ultimately be attributed to a failure to monitor NMB or a lack of understanding of neuromuscular pharmacology. 6 Our findings indicate that despite the availability of quantitative monitoring, a high proportion of our patients still arrive in PACU with residual NMB. Although it is possible our findings represent a performance issue only in our own department, each institution should consider whether they are using recommended modes of NMB monitoring and NMB reversal and should examine their incidence of residual NMB. Our findings also suggest the use of quantitative NMB monitoring alone does not preclude residual NMB and that improvements in the interpretation of NMB monitoring may be required.
Footnotes
Acknowledgements
The findings of this study were partially presented at the 2019 Euroanaesthesia Congress, Vienna, Austria.
Declaration of conflicting interests
The author(s) declared the following potential conflicts of interest with respect to the research, authorship, and/or publication of this article: Guy Cammu is a principal consultant for Merck Sharp & Dohme: he has received research grants and lecture fees over the years and performed funded research on sugammadex. The other authors have no conflicts of interest to declare.
Funding
The author(s) received no financial support for the research, authorship, and/or publication of this article.
