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Canadian Journal of Anesthesia/Journal canadien d'anesthésie
Published in: Canadian Journal of Anesthesia/Journal canadien d'anesthésie 11/2010

01-11-2010 | Reports of Original Investigations

Prediction of the time to complete a series of surgical cases to avoid cardiac operating room overutilization

Authors: Rene Alvarez, MEng, Richard Bowry, MBBS, Michael Carter, PhD

Published in: Canadian Journal of Anesthesia/Journal canadien d'anesthésie | Issue 11/2010

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Abstract

Purpose

Operating room (OR) efficiency could be improved by reducing overutilization. In this article we suggest a methodology to accurately determine the time to complete a series of surgical cases in a single cardiac OR to avoid overutilization. Our methodology includes the basic assumptions that the first case starts on time, there are no add-on cases, and there is a predetermined OR time allocation.

Methods

We studied 6,090 cases performed by the department of cardiovascular surgery service at St. Michael’s Hospital. Lognormal distributions were fitted to surgical times and turnover times. The distribution of the duration of the schedule was estimated using the Fenton-Wilkinson approximation. A simple model utilizing these distributions was then applied to three months of data to determine if overutilization could be predicted using the model.

Results

The mean difference between the actual schedule duration and the average duration was 0.19 hr (11.64 min). The difference with the second tertile cut-off point was 0.59 hr (35.40 min). Schedules that overran were correctly predicted by the average duration in 86.49% of the cases (with 12 false predictions), and they were correctly predicted by the second tertile cut-off point in 94.59% of the cases (with 26 false predictions).

Conclusions

These results suggest that the sum of the average duration of surgeries and turnover times is indeed a good estimator of the duration of the series of surgical cases. Neither the estimated averages nor the second tertile cut-off points were useful to predict overrun when used alone. The use of the estimated average duration of the schedule, validated by use of the second tertile cut-off point, could reduce overtime when allocating surgeries in a single cardiac OR.
Footnotes
1
Alvarez R, Sandoval GA, Carter M, Brown S. Allocating surgeries to a block time: a heuristic method to estimate the probability distribution of the total schedule duration by summing random surgical times. Proceedings of the XXXIV Operations Research applied to Health Services (ORAHS) Conference. Toronto, Canada 2010.
 
2
Strum D, Vargas L. Turnover Times between surgeries: a comparison of the normal and lognormal models (Abstract) 2009 CORS/ INFORMS International Meeting, The Westin Harbour Castle, Toronto, Ontario, 14-17 Jun 2009.
 
3
Wu J, Mehta NB, Zhang J. Flexible lognormal sum approximation method. Proceedings of IEEE GLOBECOM St. Louis, Missouri, USA 2005; 6: 3413-7.
 
4
Fox BL, Johnson ME, Law AM, et al. Alternative approaches for specifying input distributions and processes (panel session). Proceedings of the 22nd Conference on Winter Simulation. 1990: 382-6.
 
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Metadata
Title
Prediction of the time to complete a series of surgical cases to avoid cardiac operating room overutilization
Authors
Rene Alvarez, MEng
Richard Bowry, MBBS
Michael Carter, PhD
Publication date
01-11-2010
Publisher
Springer-Verlag
Published in
Canadian Journal of Anesthesia/Journal canadien d'anesthésie / Issue 11/2010
Print ISSN: 0832-610X
Electronic ISSN: 1496-8975
DOI
https://doi.org/10.1007/s12630-010-9371-8

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