A simple method for deciding when patients should be ready on the day of surgery without procedure-specific data

Deciding when patients should arrive for same-day-admission or ambulatory surgery is a problem at many hospitals and surgery centers. Although staff can often start cases earlier than scheduled, the potential start times are not known when each case is scheduled. Patient availability must therefore be balanced against patient waiting times and fasting times. Knowing the earliest time that a case might begin, given its scheduled start time, provides a rational basis for telling patients when to report for surgery and when to refrain from eating or drinking before their procedure.

We describe and validate a simple method for determining the earliest possible start time for a case, with only a 5% probability that staff would be able to start the case even earlier. Calculations use nonparametric methods to determine the 0.05 lower prediction bound for the start time of a case, using historical values for the scheduled and actual start times of cases performed by the same surgical suite/surgical service/day of the week combination as the case of interest. Information is not needed regarding the preceding cases performed in the same operating room. No patient or surgeon identifiable information is used.

We use results from earlier studies to provide a derivation and theoretical justification for these methods. New data confirm the validity of the results obtained and show that the required calculations are easy to implement. Individualized patient instructions can be accessed via a public website without disclosing confidential information.

We have developed a simple method for determining when patients should be ready on the day of surgery based on the start times of historical cases performed by the same surgical suite/surgical service/day of the week combination as the case of interest.