The use of neuromuscular blocking agents during surgery is associated with postoperative respiratory complications and increased risk of readmission to the hospital following ambulatory surgery. Understanding the clinical behavior of providers is essential in devising and assessing quality improvement projects since it is primarily individuals who determine the utilization of neuromuscular blocking drugs and reversal agents, not institutions. Therefore, the primary objective of this study is to determine the variability between individual anesthesia providers (attending physician, resident, nurse anesthetists) in the use of neuromuscular blocking drugs and reversal agents, using advanced statistical methods to adjust for differences in patient and procedure case mix. The investigators hypothesize that variance between individual anesthesia providers in the use of neuromuscular blocking drugs and reversal agents differs depending on provider type.

More than 400 million people receive neuromuscular blocking agents (NMBA) annually, either in the operating theatre to optimize surgical conditions, or in the intensive care unit to facilitate mechanical ventilation in those with patient-ventilator asynchrony. NMBA have been associated with increased morbidity secondary to postoperative residual neuromuscular blockade. The incidence of residual blockade is about 20-60% of patients and depends on compound and dose of NMBA reversal agent used. Despite disagreements over guidelines and thresholds to define the optimal strategy to optimize surgical conditions, there is growing evidence that very high doses of NMBA and neostigmine put the patients at risk of respiratory complications and hospital readmission. The investigators have recently shown that dedicated quality improvement initiatives substantially improve the utilization of non-depolarizing muscle relaxants and their reversal agents.

This is a retrospective, observational, multi-centric cohort study based on on-file hospital data from two institutions, Massachusetts General Hospital and Beth Israel Deaconess Medical Center, Boston, Massachusetts. The investigators will compare the utilization of NMBA cross different groups of anesthesia providers (anesthesiologists, anesthesia residents, CRNAs) who provided anesthesia care in at least 100 cases in their institution. The investigators will control our provider-specific findings for patient-, procedure-, and hospital-specific differences in NMBA utilization.

Primary objective is to determine the variability between individual anesthesia providers in the use of neuromuscular blocking drugs and reversal agents (neostigmine at Massachusetts General Hospital/MGH and neostigmine or sugammadex at Beth Israel Deaconess Medical Center/BIDMC) across provider-types (attending physician, resident, nurse anesthetists (CRNA)), experience level (number of cases done in an institution), and hospitals (MGH, BIDMC).

Potential mechanisms of the provider variability will then be examined, such as providers´age, gender, race, profession, employment status and time of the procedure (surgery conducted during daytime versus nighttime).

Additionally, the investigators will examine if the provider variance in the use of NMBA, neostigmine, and sugammadex (based on mean dose across providers and individual mean dose given for standardized surgical procedures) is associated with respiratory complications and direct costs of care.

Inclusion Criteria:

• 18 years of age or older
• Non-cardiac surgical procedure
• Endotracheally intubated for surgery and extubated at the end of the case

Exclusion Criteria:

• American Society of Anesthesiologists (ASA) Classification Status of 5 or 6
• Other surgery within a month prior to the procedure considered
• Missing covariates

Adult patients undergoing non-cardiac surgical procedure that are intubated for surgery and extubated at the end of the case.