To maximize operating room (OR) utilization, it is important to schedule into open time as many submitted add-on elective cases as possible. Typically, such cases are added on a first-come, first-serve basis. Because OR staff salaries account for the majority of OR costs, it is important to match add-on cases to times when OR staff are scheduled to work. The algorithm best suited to schedule add-on cases is not known. Dexter et al.  used computer simulation and 10 different scheduling algorithms adapted from the management sciences literature to evaluate their performance in scheduling add-on elective cases in the OR.

The authors gathered actual data from the tertiary surgical suite and ambulatory surgical center at their institution, which included the number of hours of open time available for add-on cases per day in each surgical suite and duration of each elective add-on case. The two sets of measured time data were summarized by fitting probability distributions appropriate for the data. These probability data were used in computer simulations to compare the performances of the different scheduling algorithms. The investigators evaluated four on-line algorithms that consider cases in the order submitted, and five off-line algorithms in which cases are “batched” before being scheduled and a specified cut-off time for submission of cases is used. The team also created one hybrid algorithm containing the advantages of both on-line and off-line algorithms and included this in their analysis. The end point of the simulations was OR utilization (time an OR was used divided by the time the OR was available).

The team identified the algorithm most effective for scheduling add-on elective cases in the surgical suites, which averaged zero to one elective case in each OR per day. Best Fit Descending, an off-line algorithm in which add-on elective cases are sorted based on longest to shortest with fuzzy constraints, achieved OR utilizations that were 4% larger than those achieved with the algorithm with the poorest performance. Whether implemented manually by a scheduler or programmed into a scheduling system, this algorithm can increase OR revenue without increasing the number of staffed OR hours. The authors caution that their simulation may best reflect situations in surgical suites with relatively few add-on elective cases each day, and the implementation of the algorithm will require further study.