Franklin Dexter, Craig Jarvie, Richard H. Epstein

Percentage utilization of operating room (OR) time is not an appropriate endpoint for planning additional OR time for surgeons with high caseloads, and cannot be measured accurately for surgeons with low caseloads. Nonetheless, many OR directors claim that their hospitals make decisions based on individual surgeons' OR utilizations. This incongruity could be explained by the OR managers considering the earlier mathematical studies, performed using data from a few large teaching hospitals, as irrelevant to their hospitals. The important mathematical parameter for the prior observations is the percentage of surgeon lists of elective cases that include 1 or 2 cases; "list" meaning a combination of surgeon, hospital, and date. We measure the incidence among many hospitals. Observational cohort study. 117 hospitals in Iowa from July 2013 through September 2015. Surgeons with same identifier among hospitals. Surgeon lists of cases including at least one outpatient surgical case, so that Relative Value Units (RVU's) could be measured. Averaging among hospitals in Iowa, more than half of the surgeons' lists included 1 or 2 cases (77%; P<0.00001 vs. 50%). Approximately half had 1 case (54%; P=0.0012 vs. 50%). These percentages exceeded 50% even though nearly all the surgeons operated at just 1 hospital on days with at least 1 case (97.74%; P<0.00001 vs. 50%). The cases were not of long durations; among the 82,928 lists with 1 case, the median was 6 intraoperative RVUs (e.g., adult inguinal herniorrhaphy). Accurate confidence intervals for raw or adjusted utilizations are so wide for individual surgeons that decisions based on utilization are equivalent to decisions based on random error. The implication of the current study is generalizability of that finding from the largest teaching hospital in the state to the other hospitals in the state.