Adam Meyers ^1* Mertcan Daysalilar ¹ Arman Dagal ^2,3 Michael Wang ³ Onur Kutlu ⁴ Mehmet Akcin ^1,4

• ¹ Department of Industrial and Systems Engineering, College of Engineering, University of Miami, Coral Gables, Florida, United States
• ² Department of Anesthesiology, Perioperative Medicine and Pain Management, Leonard M. Miller School of Medicine, University of Miami, Miami, Florida, United States
• ³ Department of Neurological Surgery, Leonard M. Miller School of Medicine, University of Miami, Miami, Florida, United States
• ⁴ DeWitt Daughtry Family Department of Surgery, Leonard M. Miller School of Medicine, University of Miami, Miami, Florida, United States

Introduction: Operating room (OR) efficiency is a key factor in determining surgical healthcare costs. To enable targeted changes for improving OR efficiency, a comprehensive quantification of the underlying sources of variability contributing to OR efficiency is needed. Previous literature has focused on select stages of the OR process or on aggregate process times influencing efficiency. This study proposes to analyze the OR process in more fine-grained stages to better localize and quantify the impact of important factors. Methods: Data spanning from 2019-2023 were obtained from a surgery center at a large academic hospital. Linear mixed models were developed to quantify the sources of variability in the OR process. The primary factors analyzed in this study included the primary surgeon, responsible anesthesia provider, primary circulating nurse, and procedure type. The OR process was segmented into eight stages that quantify eight process times, e.g., procedure duration and procedure start time delay. Model selection was performed to identify the key factors in each stage and to quantify variability. Results: Procedure type accounted for the most variability in three process times and for 44.2\% and 45.5\% of variability, respectively, in procedure duration and OR time (defined as the total time the patient spent in the OR). Primary surgeon, however, accounted for the most variability in five of the eight process times and accounted for as much as 21.1\% of variability. The primary circulating nurse was also found to be significant for all eight process times. Discussion: The key findings of this study include the following. (1) It is crucial to segment the OR process into smaller, more homogeneous stages to more accurately assess the underlying sources of variability. (2) Variability in the aggregate quantity of OR time appears to mostly reflect the variability in procedure duration, which is a subinterval of OR time. (3) Primary surgeon has a larger effect on OR efficiency than previously reported in the literature and is an important factor throughout the entire OR process. (4) Primary circulating nurse is significant for all stages of the OR process, albeit their effect is small.