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J Clin Anesth. 2007 May;19(3):198-203.

Identification of systematic underestimation (bias) of case durations during case scheduling would not markedly reduce overutilized operating room time.

Author information

  • 1Division of Management Consulting, Department of Anesthesia, University of Iowa School of Medicine, Iowa City, IA 52242, USA. franklin-dexter@uiowa.edu



If a case has a high probability of taking longer than scheduled, then increasing the case's scheduled duration could reduce over-utilized operating room (OR) time. We studied surgeons' and schedulers' case scheduling behavior to evaluate whether such a strategy would be useful.


Observational study.


University hospital.


The probability of each of 66,561 cases taking longer than scheduled was estimated with an accuracy to within 1-2%.


Overall underestimation by surgeons and schedulers was 22 minutes for each 8 hours of used operating room (OR) time. If a 90% or 95% chance of taking longer than scheduled were required to conclude that a case's duration was deliberately underestimated, and if such cases' scheduled durations were changed, overall underestimation would be reduced by only 0.2 or 0.9 minutes per 8 hours of used OR time because only 0.1% or 0.6% of used OR time met that criterion. In contrast, underestimation would be reduced by 20 minutes if the cases identified were those with only a 50% to 60% chance of taking longer than scheduled because they accounted for more than 40% of OR time. Persistent underestimation of cases' durations was caused not by poor decisions for a few outlier cases, but instead by slight underestimation for many cases. Surgeons' and schedulers' behavior that fit cases into staffed (allocated) OR time was to underestimate slightly the duration of many cases.


The impact of inaccurate, scheduled case duration on staffing costs and unpredictable work hours can be reduced by allocating appropriate total hours of OR time (ie, staffing) for the cases that will get done, regardless of the inaccuracy of the scheduled durations of those cases.

[PubMed - indexed for MEDLINE]
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