title: Modeling procedure and surgical times for current procedural terminology-anesthesia-surgeon combinations and evaluation in terms of case-duration prediction and operating room efficiency: a multicenter study.
abstract: BACKGROUND
  Gains in operating room (OR) scheduling may be obtained by using accurate statistical models to predict surgical and procedure times. The 3 main contributions of this article are the following: (i) the validation of Strum's results on the statistical distribution of case durations, including surgeon effects, using OR databases of 2 European hospitals, (ii) the use of expert prior expectations to predict durations of rarely observed cases, and (iii) the application of the proposed methods to predict case durations, with an analysis of the resulting increase in OR efficiency.
  
  
  METHODS
  We retrospectively reviewed all recorded surgical cases of 2 large European teaching hospitals from 2005 to 2008, involving 85,312 cases and 92,099 h in total. Surgical times tended to be skewed and bounded by some minimally required time. We compared the fit of the normal distribution with that of 2- and 3-parameter lognormal distributions for case durations of a range of Current Procedural Terminology (CPT)-anesthesia combinations, including possible surgeon effects. For cases with very few observations, we investigated whether supplementing the data information with surgeons' prior guesses helps to obtain better duration estimates. Finally, we used best fitting duration distributions to simulate the potential efficiency gains in OR scheduling.
  
  
  RESULTS
  The 3-parameter lognormal distribution provides the best results for the case durations of CPT-anesthesia (surgeon) combinations, with an acceptable fit for almost 90% of the CPTs when segmented by the factor surgeon. The fit is best for surgical times and somewhat less for total procedure times. Surgeons' prior guesses are helpful for OR management to improve duration estimates of CPTs with very few (<10) observations. Compared with the standard way of case scheduling using the mean of the 3-parameter lognormal distribution for case scheduling reduces the mean overreserved OR time per case up to 11.9 (11.8-12.0) min (55.6%) and the mean underreserved OR time per case up to 16.7 (16.5-16.8) min (53.1%). When scheduling cases using the 4-parameter lognormal model the mean overutilized OR time is up to 20.0 (19.7-20.3) min per OR per day lower than for the standard method and 11.6 (11.3-12.0) min per OR per day lower as compared with the biased corrected mean.
  
  
  CONCLUSIONS
  OR case scheduling can be improved by using the 3-parameter lognormal model with surgeon effects and by using surgeons' prior guesses for rarely observed CPTs. Using the 3-parameter lognormal model for case-duration prediction and scheduling significantly reduces both the prediction error and OR inefficiency.
authors.affiliation: Institute of Health Policy and Management, Erasmus University Rotterdam, The Netherlands. stepaniak@bmg.eur.nl
authors.forename: Pieter S
authors.initials: PS
authors.lastname: Stepaniak
authors.forename: Christiaan
authors.initials: C
authors.lastname: Heij
authors.forename: Guido H H
authors.initials: GH
authors.lastname: Mannaerts
authors.forename: Marcel
authors.initials: M
authors.lastname: de Quelerij
authors.forename: Guus
authors.initials: G
authors.lastname: de Vries
mesh_terms: D000776:Anesthesiology / Q000458:organization & administration* / Q000706:statistics & numerical data; D001071:Appointments and Schedules; D039702:Current Procedural Terminology; D019992:Databases as Topic; D017598:Efficiency, Organizational / Q000706:statistics & numerical data*; D005060:Europe; D006784:Hospitals, Teaching / Q000706:statistics & numerical data; D006801:Humans; D008505:Medical Staff, Hospital / Q000458:organization & administration* / Q000706:statistics & numerical data; D017146:Models, Organizational; D015233:Models, Statistical; D009870:Operating Room Information Systems; D009873:Operating Rooms / Q000458:organization & administration* / Q000706:statistics & numerical data; D010561:Personnel Staffing and Scheduling / Q000458:organization & administration* / Q000706:statistics & numerical data; D015203:Reproducibility of Results; D012189:Retrospective Studies; D013514:Surgical Procedures, Operative / Q000706:statistics & numerical data*; D013997:Time Factors; D017748:Time Management / Q000458:organization & administration; D000078329:Workforce; D016526:Workload / Q000706:statistics & numerical data