Neuromuscular blocking agents' (NMBA) use during surgery is associated with postoperative respiratory complications and increased risk of readmission to the hospital following ambulatory surgery. Residual neuromuscular block (rNMB) after surgery is difficult to identify. We have recently developed the REsidual neuromuscular block Prediction Score (REPS), that predicts the risk for postoperative rNMB. Our primary objective is now to assess the predictive ability of the REPS for respiratory complications within seven days following general anaesthesia. The secondary objective is to compare the predictive values of REPS and train-of-four (TOF)-ratio below 0.90 for respiratory complications.

Residual neuromuscular blockade occurs in about 20-60% of patients and depends on compound and dose of NMBA reversal agent used. While on the one hand, NMBAs optimize surgical conditions and facilitate mechanical ventilation in patients with ventilator asynchrony, on the other hand, these agents have been associated with respiratory complications and increased risk of readmission after ambulatory surgery. A consensus in regard to guidelines and thresholds to define the optimal strategy to optimize surgical conditions is yet to be achieved. We have shown that utilization of non-depolarizing muscle relaxants and their reversal agents can be improved by dedicated quality improvement techniques. We have also recently developed the REPS, a tool that predicts postoperative rNMB.

This is a retrospective, observational, cohort study based on on-file hospital data from Beth Israel Deaconess Medical Center, Boston, Massachusetts.

The primary aim is to validate the dichotomized REPS (high-risk versus low-risk for rNMB which corresponds to a REPS >4 and <4, respectively) for the outcome of postoperative respiratory complications with BIDMC data. The investigators will utilize the pre-defined variables identified to predict residual neuromuscular blockade (REPS) at BIDMC.

The secondary aim is to compare the predictive values of the dichotomized REPS with dichotomized train-of-four (TOF)-ratio (low TOF-ratio versus high TOF ratio which corresponds to a TOF-ratio <0.9 and >=0.9, respectively) for respiratory complications.

Inclusion Criteria:

• 18 years or older
• Non-cardiac surgery
• General anesthesia with intermediate-acting NMBAs (atracurium, cisatracurium, vecuronium, or rocuronium)
• Extubated in the operating room
• PACU after surgery

Exclusion Criteria:

• American Society of Anesthesiology (ASA) Physical Status Classification of 5 or 6
• Did not receive neuromuscular blocking agents
• Missing last covariates

Adult patients who underwent non-cardiac surgery under general anesthesia with intermediate-acting NMBAs and are admitted to the Post-Anaesthesia Care Unit (PACU) after surgery.