RNMB remains as a significant factor in the causation of postoperative pulmonary complications, and is often underestimated by anesthesiologists. Acceleromyography is the recommended clinical tool to monitor a muscular blockade. Although this has been strongly advocated, this approach remains uncomfortable for conscious patients when assessing the RNMB. Quantitative monitoring is not routinely and intraoperatively used, and in any case, it does not rule out the possibility of muscle weakness in the postoperative period [17, 18]. Despite the use of neostigmine reversal, RNMB may still occur. Quantitative monitoring suggests that after intermediate-acting nondepolarizing NMBA use, up to 60% of patients may have a clinically meaningful RNMB [19, 20]. However, the determination of whether the technique is a valid method for neuromuscular evaluation has become a major subject for debate.
Diaphragm ultrasound can be an effective alternative. The introduction of ultrasound makes the assessment of the function of the main respiratory muscle (the diaphragm) possible using a noninvasive, bedside, repeated, safe and radiation-free tool . After the use of NMBAs, the diaphragm lastly relaxes, and initially recovers . Diaphragm dysfunction is associated with respiratory insufficiency, hypoxia, atelectasis, and prolonged mechanical ventilation, ICU and prolonged hospital stay [23, 24]. Therefore, the evaluation of diaphragm function is helpful to reduce the occurrence of postoperative pulmonary complications.
In the present study, the investigators attempted to assess diaphragm function in conscious patients using ultrasound. The data revealed that the DE was significantly higher in the NEO group than in the NS group after extubation. Furthermore, upon leaving the PACU, in the NEO group, this tended to the complete recovery of where the baseline diaphragm excursion occurred. And Cappellini et al. performed a study in patients who, after rocuronium administration, received neostigmine or sugammadex: the authors found an early (0 min) but not long-lasting (30 min) association between diaphragm failure and recovery drug treatment . Those outcomes may be suggested the reversal drugs can be helpful to the recovery of muscle function after use of neuromuscular blocking agents during early period of postoperation.
Postoperative pneumonia is a dominating hospital-acquired infection worldwide [26, 27]. Pneumonia has been associated with related mortality, longer hospital stay, more postoperative hospital readmissions, and increased health costs [28, 29]. In the present study, the investigators chose postoperative pneumonia as one of the follow-up outcomes. Among the 150 patients, 21 patients were lost follow up, in which 8 patients were from the antagonized group and 13 patients were from the unantagonized group, with a loss rate of 14%. The reasons were, as follows: (1) the patients could not be contacted; (2) the information of postoperative nursing records was incomplete; (3) there were defects in the laboratory results. In the data analysis, the available data, including hypoxemia, hypercapnia and respiratory insufficiency, were included in the statistical analysis, except for missing postoperative pneumonia information. There was no statistical difference in demographic characteristics between the patients who were lost follow-up and those who were included in the present study. The incidence of PPCs was similar for the two groups. Furthermore, 13 patients had hypoxemia in the PACU (8.67%). After extubation, the incidence of hypercapnia was 46%, and the incidence decreased to 3.33% when they left the PACU. Moreover, 9.33% of patients had respiratory insufficiency after extubation. However, the incidence of respiratory insufficiency after extubation was higher in the NEO group, when compared to the NS group during postoperative follow-up. With neostigmine, RNMB cannot always be excluded, especially when an intermediate or long-lasting muscle relaxant is administered. Reversal of NMBAs with neostigmine leads to neostigmine-induced RNMB [30, 31]. Neostigmine does not improve the oxygenation of patients in PACU and was associated with an increased incidence of postoperative atelectasis . Neostigmine administered in the rats after recovery of TOF impairs upper airway integrity and genioglossus and diaphragm muscle function . High dose of neostigmine (over 60ug/kg) increases the risk of respiratory complications unrelated to the effects of NMBAs . Maybe it’s more important that the timing and reasonable dosage of neostigmine. In recent years, conflicting data have indicated that the use of reversal agents or Acceleromyography monitoring could not decrease the risk of PPCs.
Due to anatomical reasons, diaphragm movement is often interfered during thoracic and abdominal surgery. Therefore, the reasons for postoperative diaphragm dysfunction remain complex and uncertain. As far as this kind of surgery is concerned, part of the reasons of PPCs come from the influence of the operation itself. In ruling out this kind of operation, focus should be given in analyzing the relationship among neuromuscular blocking agents, diaphragm function, and postoperative pulmonary complications. The present study had some limitations. Primarily, the investigators only enrolled patients who had ASA physical status I or II, were within 18–65 years old, and had no lung disease. The other conditions of these patients could not be determined, such as advanced age, obesity, or the presence of chronic obstructive pulmonary disease. Furthermore, neurosurgery had a lower incidence of PPCs, when compared to thoracoabdominal surgery. The next step is to expand the research population and types of operation, in order to further research the relationship of DE and postoperative pulmonary complications.
In conclusion, RNMB is still a frequent and risky postoperative adverse reaction after the administration of NMBAs. The reversal drugs may be helpful to the recovery of diaphragm function, however it cannot reduce the incidence of PPCs. Diaphragm ultrasound could be an attractive, non-invasive, promising tool to evaluate diaphragm function after neuromuscular blockade. More research will be needed to optimize the peri-operation management.