Rational planning of operating lists: a prospective comparison of 'booking to the mean' vs. 'probabilistic case scheduling' in urology.
The efficient use of operating theatres requires accurate case scheduling. One common method is 'booking to the mean'. Here, the mean times for individual operations are summed to approximate the time allocated to the list. An alternative approach is 'probabilistic scheduling'. Here, the means and standard deviation of the individual case times are combined to estimate the probability that the planned list will finish on time. This study assessed how probabilistic booking would have changed list utilisation, over-running and case cancellations in 60 urology lists during eight months that had been 'booked to the mean'. Booking to the mean resulted in 53/60 (88%) lists over-running and correctly predicted the finish times in just 13% of lists. Out of 264 patients, 36 (14%) were cancelled on the day due to over-runs in 24/60 (40%) lists. In contrast, probabilistic scheduling correctly predicted an over-run or under-run in 77% of lists, which would have allowed the case mix to be adjusted to prevent cancellation and optimise utilisation.