The association between residual neuromuscular blockade (RNMB) and critical respiratory events: a prospective cohort study

BACKGROUND: Inadequate neuromuscular recovery might impair pulmonary function among adult patients who undergo general anaesthesia and might thus contribute to critical respiratory events in the post-anaesthesia care unit (PACU). The pilot study aims to understand the baseline incidence of residual neuromuscular blockade (RNMB) and postoperative critical respiratory events (CREs), which are described in a modified Murphy’s criteria in the PACU. METHOD: This is a prospective cohort study from January to March 2017 from a tertiary hospital in Saudi Arabia with thirty adult patients over 18 years old scheduled for elective surgery under general anaesthesia with neuromuscular blocking drugs (NMBDs) who were enrolled in the study. The Mann-Whitney U tests, chi-square tests and independent-samples T tests were used. The train-of-four (TOF) ratios were measured upon arrival in the PACU by using acceleromyography with TOF-Scan. Subjects’ demographics, perioperative data and the occurrence of postoperative CREs in the PACU were recorded. RESULTS: Twenty-six (86.7%) patients out of thirty in the study have received rocuronium as NMBDs whilst neostigmine as a reversal drug with only 23 (76.7%). The incidence of RNMB (TOF ratio < 0.9) was in 16 patients (53.3%). The incidence of RNMB was significantly higher in female patients (p = 0.033), in patients who had not undergone quantitative neuromuscular monitoring before extubation (p = 0.046) and in patients with a shorter duration of surgery (p = 0.001). Postoperative CREs occurred in twenty patients (66.7%), and there were significantly more of these CREs among patients with RNMB (p = 0.001). In addition, a statistically significant difference was observed in the occurrence of CREs according to body mass index (p = 0.047). CONCLUSION: This research showed that RNMB is a significant contributing factor to the development of critical respiratory events during PACU stay. Therefore, routine quantitative neuromuscular monitoring is recommended to reduce the incidence of RNMB.