Scheduling operating rooms: achievements, challenges and pitfalls

TL;DR: The recent OR planning and scheduling literature is classified into tables regarding patient type, used performance measures, decisions made, OR up- and downstream facilities, uncertainty, research methodology and testing phase, to help researchers and practitioners to select new relevant articles.

Abstract: In hospitals, the operating room (OR) is a particularly expensive facility and thus efficient scheduling is imperative. This can be greatly supported by using advanced methods that are discussed in the academic literature. In order to help researchers and practitioners to select new relevant articles, we classify the recent OR planning and scheduling literature into tables regarding patient type, used performance measures, decisions made, OR up- and downstream facilities, uncertainty, research methodology and testing phase. Based on these classifications, we identify trends and promising topics. Additionally, we recognize three common pitfalls that hamper the adoption of research results by stakeholders: the lack of a clear choice of authors on whether to target researchers (contributing advanced methods) or practitioners (providing managerial insights), the use of ill-fitted performance measures in models and the failure to understandably report on the hospital setting and method-related assumptions. We provide specific guidelines that help to avoid these pitfalls. First, we show how to build up an article based on the choice of the target group (i.e., researchers or practitioners). Making a clear distinction between target groups impacts the problem setting, the research task, the reported findings, and the conclusions. Second, we discuss points that need to be considered by researchers when deciding on the used performance measures. Third, we list the assumptions that need to be included in articles in order to enable readers to decide whether the presented research is relevant to them.

Summary

1 Introduction

• Health care has a heavy financial burden for governments within the European Union as well as in the rest of the world.
• Hospitals are responsible for more than one third of these expenditures [86].
• Out of the many aspects of OR management, the authors focus their attention on planning and scheduling problems (the terms planning and scheduling are in this article used interchangeably).
• To their knowledge, there is no recent review on OR planning that considers these latter two aspects.
• In order to cover these aspects, the authors define the following three research tasks.

2 Search Method and Other Reviews

• In Sect. 2.1, the authors introduce the procedure that they used to identify relevant articles.
• Based on the scope of the literature review, the authors distinguish between three levels.
• The second level targets Scheduling operating rooms: Achievements, challenges and pitfalls 3 the OR together with other areas that can be of interest in a hospital such as bed planning [26] or patient flow planning.
• Other reviews structure the literature on the basis of managerial or functional levels [207] and problem characteristics, e.g., the type of the arrival process [110].
• Guerriero and Guido [105] conclude that the three hierarchical levels are rarely studied together and argue that the tactical level has received increased attention in the last ten years.

3 Descriptive Fields

• Each field analyzes articles from a different perspective, which can be either problem or technically oriented.
• The trade-off between patient waiting time and OR overtime represents the balance between an adequate degree of responsiveness to non-electives and the efficient use of OR resources.
• There is already a substantial amount of research on appointment scheduling in outpatient centers, but those results usually rely on modeling assumptions that do not apply to outpatient surgery.
• In the literature, various other terms are used to identify typical OR related scheduling problems.
• Papers that are categorized in the column or row with label ‘Other’ examine a wide variety of aspects.

4 Common pitfalls

• In this section the authors go one step further and describe some of the general observations and conclusions they made.
• This is a problem for both theory- and practice-oriented articles and could be prevented by having a clear distinction between both types of articles concerning their target group and the resulting conclusions.
• As many PMs are used independently of the problem setting, one might wonder whether PMs are generally used in an appropriate way.
• The authors distinguish between setting specific (often explicit) and method specific (often implicit) assumptions (Table 15).
• The authors Scheduling operating rooms: Achievements, challenges and pitfalls 25 find it important to emphasize the necessity to include a description of method specific assumptions in articles as they noticed that this is not always the case.

5 Conclusion

• The authors classified the OR planning and scheduling literature over the years 2000-2014 with regard to the patient type, the different performance measures, the decision that has to be made, the integration of OR supporting units, the incorporation of uncertainty, the operations research methodology and the testing phase.
• Results from operations research methods are in the majority of the cases not used in reality because, amongst other things, the models are not realistic enough.
• Additionally, it would make it easier for both practi- tioners and researchers to identify articles that are relevant for them; many PMs (e.g., overtime) are used in articles indifferently of the tackled problem; important information is occasionally missing from articles (Table 15).
• Generally articles where analytical methods (e.g., Markov models) are used, will often assume estimated durations to be equal, as this is a strong assumption one should be careful when generalizing the results of these methods to inpatient scheduling.
• In order to avoid these pitfalls, the authors conclude that researchers need to clearly define the target group (i.e., researchers or practitioners) since this choice impacts all aspects of the research (Sec. 4.1).

Figures

Fig. 2 The majority of articles relate to the elective patient. Contrary to what might be expected, the share of outpatient related articles is not increasing. As some articles deal with both elective and non-elective patients, the sum of both values might add up to more than 100%

Table 14 Selecting appropriate PMs should not be done based on their popularity in the literature

Table 7 Stochasticity is frequently taken into account

Fig. 6 On average, more than half of the papers take some type of uncertainty into account

Table 10 The likeliness to use stochasticity or method (Columns) with a specific field (Rows) compared to using it without the specific field (¬R)

Table 3 The type of patient that is considered in articles is not always specified and, especially for the elective patient case, it is not always clear whether an inpatient or outpatient setting is researched

Table 11 Conditional probabilities of various performance measures given different fields

Table 12 Conditional probabilities of various constraints given different fields

Fig. 3 Overtime, despite experiencing a slight decline, is still the most frequently used performance measure. From 2008 onward, preference-related measures became increasingly popular, followed by a decline in interest after 2010

Table 6 In an integrated OR, supporting facilities such as the ICU, the PACU and the wards are considered

Fig. 5 An integrated OR planning and scheduling process is considered in around 50% of articles. The downstream units (i.e., PACU, ward, ICU) are the most common included supporting units. As only the three main supporting facilities are shown, their count does not necessarily sum up to the total of the integrated approaches

Table 1 The graphs showing trends are based on papers in the third column, while the tables additionally include the papers in the second column

Fig. 7 From the major solution techniques used in the literature only MP experienced a strong growth in popularity

Fig. 4 The assignment of dates and rooms is increasingly popular in the literature, whereas the interest in the time assignment step (e.g., sequencing) shows a more variable pattern, e.g., it has lost some of its popularity around 2010, but regained it towards 2014

Fig. 1 The number of published technical articles in OR scheduling has been growing over the last decade

Fig. 8 Even though most data used in the literature are based on real data, it does not mean that the methods are applied in reality

Table 9 For testing purposes, both theoretic and real data are frequently used

Table 8 Different solution techniques are used in the literature: analytical procedures (e.g., queueing theory), mathematical programming, dedicated branch-and-bound, scenario analysis (or sensitivity analysis), simulation and various heuristics

Table 5 The matrix defines the decision (columns) and assignment (rows) level

Table 15 Setting and method specific assumptions need to be included in papers on OR planning

Table 13 A clearer distinction between theory- and practice-oriented articles benefits readers as it makes it easier for them to identify articles that are relevant to them

Full text

Scheduling operating
rooms: achievements,
challenges and pitfalls
Samudra M, Van Riet C, Demeulemeester E, Cardoen
B, Vansteenkiste N, Rademakers F.
KBI_1608

Scheduling operating rooms:
Achievements, challenges and pitfalls
Michael Samudra · Carla Van Riet · Erik Demeulemeester · Brecht
Cardoen · Nancy Vansteenkiste · Frank E. Rademakers
Abstract In hospitals, the operating room (OR)
is a particularly expensive facility and thus effi-
cient scheduling is imperative. This can be greatly
supported by using advanced methods that are
discussed in the academic literature. In order to
help researchers and practitioners to select new
relevant articles, we classify the recent OR plan-
ning and scheduling literature into tables using
patient type, used performance measures, deci-
sions made, OR supporting units, uncertainty, re-
search methodology and testing phase. Addition-
ally, we identify promising practices and trends
and recognize common pitfalls when research-
ing OR scheduling. Our findings indicate, among
others, that it is often unclear whether an arti-
cle mainly targets researchers and thus contributes
advanced methods or targets practitioners and
consequently provides managerial insights. More-
over, many performance measures (e.g., overtime)
are not always used in the correct context. Fur-
thermore, we see that important information that
would allow readers to determine whether the re-
ported research results are relevant to them is of-
ten missing. In order to avoid these pitfalls, we
conclude that researchers need to state whether
they target researchers or practitioners, motivate
the choice of the used performance measures and
mention both setting and method specific assump-
tions.
M. Samudra, C. Van Riet, E. Demeulemeester, B. Cardoen
Faculty of Economics and Business, KU Leuven
E-mail: carla.vanriet@kuleuven.be (

)
B. Cardoen
Vlerick Business School, Faculty of Economics and Busi-
ness, KU Leuven
N. Vansteenkiste, F. Rademakers
University hospital Leuven
Keywords Health care management · Surgery
scheduling · Operating room planning · Review
1 Introduction
Health care has a heavy financial burden for gov-
ernments within the European Union as well as
in the rest of the world. Additionally, while grow-
ing economies and newly emerging technologies
could lead us to believe that supporting our re-
spective national health care systems might get
less expensive over time, data show that this is not
the case.
For example, within the USA, the National
Health Expenditure as a share of the Gross Do-
mestic Product (GDP) was 17.4% in 2013 [54].
On the European continent, even though large dif-
ferences exist across member states, health care
expenditure as a share of the GDP was 8.7% in
2012 [193]. Hospitals are responsible for more
than one third of these expenditures [86].
Within the hospital, considerable attention is
given to operating rooms (ORs) as they represent
a significant segment of hospital costs [120]. Out
of the many aspects of OR management, we focus
our attention on planning and scheduling prob-
lems (the terms planning and scheduling are in this
article used interchangeably).
Given the importance of OR scheduling, it is
not surprising that many research groups from the
operations research community provide solution
approaches to the problems that affect it. Reviews
on this literature are important as they help re-
searchers to select relevant articles for their re-
search setting and serve as a guide for practition-
ers (e.g, hospital manager) to quickly find papers
that can contain useful managerial insights.

2 M. Samudra, C. Van Riet, E. Demeulemeester, B. Cardoen, N. Vansteenkiste, F. Rademakers
Additionally, reviews preferably cover the fol-
lowing two important aspects. First, they help
to identify promising practices and shows recent
trends (i.e., hot topics). Second, they identify com-
mon pitfalls or important aspects to consider when
doing researching in this field. To our knowledge,
there is no recent review on OR planning that con-
siders these latter two aspects.
In order to cover these aspects, we define the
following three research tasks. First, to classify
the recent OR planning and scheduling literature
(Sec. 3.1-3.7) using a simple, but comprehensive
framework. For this task, we build up on the work
carried out by Cardoen et al. [42] and Demeule-
meester et al. [60]. Second, to look for evolutions
over time, common approaches and relations be-
tween the different classification fields (Sec. 3.1-
3.8). Third, to identify the common pitfalls (e.g.,
information that we found missing in some arti-
cles) and to develop guidelines that can help re-
searchers to avoid them (Sec. 4.1-4.3).
The purpose of the remaining sections is to ex-
plain the research method (Sec. 2.1), to position
this paper in the existent group of reviews (Sec.
2.2), to introduce the classification fields (intro-
duction of Sec. 3), to discuss the limitations of this
study (Sec. 4.4) and to describe our main conclu-
sions (Sec. 5).
2 Search Method and Other Reviews
In Sect. 2.1, we introduce the procedure that we
used to identify relevant articles. In Sect. 2.2, we
discuss the structure and scope of reviews written
on similar topics and position our review within
the context of this existing literature.
2.1 Search Method
We searched the databases Pubmed and Web of
Science for relevant articles, which are written
in English and appeared in 2000 or afterwards.
Search phrases included combinations of the fol-
lowing words: operating, surgery, case, room, the-
atre(er), scheduling, planning and sequencing. We
searched in both titles and abstracts and in addi-
tion checked the complete reference list of any
already found article. As we endeavored to con-
duct the search process in an unbiased way, we be-
lieve we have obtained a set of articles that objec-
tively represents the literature on OR planning. At
the end of the search procedure, we identified 216
technically oriented papers. Note that we chose to
Table 1 The graphs showing trends are based on papers in
the third column, while the tables additionally include the
papers in the second column
2000-2003 2004-2014
Journal 24 137
Proceedings 3 42
Other 0 10
Total 27 189
investigate trends only from 2004 onwards as in
the preceding years not enough articles were pub-
lished to get reliable results (Table 1).
We define an article as “technical” if it con-
tains an algorithmic description of a method di-
rectly related to OR scheduling. Some articles
are missing this algorithmic component and in-
stead provide managerial insights. Those articles
are excluded from the classification tables, as not
all classification fields apply to them, but some
of their insights are mentioned in the text. The
quantitative descriptions provided in Sec. 3.1-3.8,
which give insights into the changing trends set by
the research community, are exclusively based on
the technical contributions.
The majority of the included articles are re-
cent publications (Fig. 1). This reflects the trend
that the amount of published technical articles
has been increasing significantly in the recent ten
years.
We do not include topics related to business
process reengineering, the impact of introducing
new technologies, facility design or long-term OR
expansion. Also, articles that deal with appoint-
ment scheduling are excluded from this review.
This is the case as some of the basic assumptions
that apply to appointment scheduling are not valid
for surgery scheduling. For a review on appoint-
ment scheduling, we refer to [48].
2.2 Other Reviews
In the past 60 years, a large body of literature on
OR planning and scheduling has been published.
The literature has been structured and reviewed
by several authors, using a variety of classification
techniques and frameworks. We grouped these re-
views based on their scope and structure (Table 2).
Based on the scope of the literature review, we
distinguish between three levels. The first level
purely focuses on the OR department (including
the post-anesthesia care unit (PACU) and the in-
tensive care unit (ICU)). The second level targets

Scheduling operating rooms: Achievements, challenges and pitfalls 3
Number of
published
articles
0
33
2004 20142009
Fig. 1 The number of published technical articles in OR
scheduling has been growing over the last decade
the OR together with other areas that can be of in-
terest in a hospital such as bed planning [26] or
patient flow planning. The third level covers OR
management in the broader context of patient care
and therefore often includes different care services
[128].
In some of the literature reviews articles are
classified based on the three hierarchical decision
levels: strategic (long-term), tactical (medium-
term) and operational (short-term). The strategic
decision level involves decisions that affect both
the number and the type of performed surgeries.
The tactical level usually involves the construction
of a cyclic schedule, which assigns time blocks to
surgeons or surgeon groups. The final, operational
level deals mostly with daily staffing and surgery
scheduling decisions. Guerriero and Guido [105]
also discuss papers that include a mix of the three
levels. Similarly, Vissers et al. [262] propose a
hierarchical framework for production control in
healthcare. They distinguish between five levels
and discuss for each level, amongst others, the
type of decisions, the time horizon and the in-
volved decision makers. With respect to the op-
erational level, a further distinction can be made
between off-line (i.e., before schedule execution)
and on-line (i.e., during schedule execution) ap-
proaches [112].
In other literature reviews custom categories
are used (Table 2). As such, Brailsford and Vis-
sers [36] use the product life cycle stages to re-
view 35 years of papers presented at the ORAHS
conference. Moreover, Erdogan and Denton [82]
review the literature according to the applied so-
lution approach. Przasnyski [210] structures the
literature based on general areas of concern, such
as cost containment. Other reviews structure the
literature on the basis of managerial or functional
levels [207] and problem characteristics, e.g., the
type of the arrival process [110].
Most literature reviews are not only reference
points to articles, but also point out topics for fu-
ture research. Guerriero and Guido [105] conclude
that the three hierarchical levels are rarely stud-
ied together and argue that the tactical level has
received increased attention in the last ten years.
In contrast, Hans and Vanberkel [112] argue that
future research should focus more on the tactical
level.
Also, May et al. [179] make suggestions and
argue that it might be promising to broaden the
focus from operations research techniques to the
economic and project management aspects of
surgery scheduling. Additionally, Vissers et al.
[262] suggest to put a larger emphasis on the mul-
tidisciplinary aspects of patient flow control sys-
tems and suggest to experiment with the effect of
grouping patients in new ways, such as based on
their length of stay (LOS) or surgery duration.
Furthermore, several authors emphasize that
more research could be done on on-line reschedul-
ing performed close to or on the day of surgery.
Dexter et al. [73] provide a review on the few pa-
pers that include that type of decisions and empha-
size the importance of the following four points:
patient safety, open access to OR time, maximiz-
ing OR efficiency (defined as minimal overutilized
OR time) and minimizing patient waiting time.
Other reviews emphasize the need for more de-
tailed models on the seasonality of demand, for
more realistic constraints for surgeon and patient
preferences and for a larger focus on the entire
care pathway.
We generally observe in reviews that topics
such as staffing are often excluded and thus treated
separately from the resource related decision mak-
ing problems. Finally, we also observe that, un-
like in the diagnostic imaging scheduling litera-
ture, most focus is on models where patients are
scheduled in batches and not one-by-one.

4 M. Samudra, C. Van Riet, E. Demeulemeester, B. Cardoen, N. Vansteenkiste, F. Rademakers
Table 2 Existing reviews differ in their scope (rows) and
classification structure (columns)
Hierarchical Custom
categories categories
OR [105, 112] [42, 60, 73, 82, 109,
167, 179, 210, 219]
Hospital [26, 27, 32, 262] [27, 32, 137, 231, 232,
250, 255]
Health care [112, 127, 128] [36, 110, 112, 127,
128, 207]
Reviewing the literature according to hierarchal categories
is a common approach. Articles appearing twice in the ta-
ble use a multi-dimensional classification structure
In this review, we propose a structure that is
based on descriptive fields. We are not using hier-
archical levels, since the boundaries between these
levels can vary considerably for different settings
and hence are often perceived as vague and in-
terrelated [230]. Furthermore, this categorization
seems to lack an adequate level of detail.
Moreover, other taxonomies that use one spe-
cific characteristic of the paper (e.g., solution tech-
nique), might prohibit the reader from easily find-
ing a paper on a certain topic. For example, when
a researcher is interested in finding papers on OR
utilization, a taxonomy based on the solution tech-
nique does not seem very helpful. We think that
the use of descriptive fields avoids these prob-
lems.
3 Descriptive Fields
Each field analyzes articles from a different per-
spective, which can be either problem or tech-
nically oriented. In particular, we distinguish be-
tween seven fields:
• Patient characteristics (Sect. 3.1): reviewing
the literature according to the elective (in-
patient, outpatient) or non-elective (urgency,
emergency) status of the patient;
• Performance measures (Sect. 3.2): discussing
the performance measures (PM) such as uti-
lization, idle time, waiting time, preferences,
throughput, financial value, makespan and pa-
tient deferral;
• Decision delineation (Sect. 3.3): indicating
what type of decision has to be made (date,
time, room and capacity) and whether this de-
cision applies to a medical discipline, a sur-
geon or a patient (type);
• Supporting facilities (Sect. 3.4): discussing
whether an approach includes supporting
units, e.g., PACU and ICU;
• Uncertainty (Sect. 3.5): indicating to what
extent researchers incorporate uncertainty
(stochastic versus deterministic approaches);
• Operations research methodology (Sect. 3.6):
providing information on the type of analysis
that is performed and the solution or evalua-
tion technique that is applied;
• Testing phase (Sect. 3.7): covering the infor-
mation on the testing (data) of the research and
its implementation in practice.
The structure we use is meant to balance be-
tween simplicity and comprehensiveness. It pro-
vides a simplified, but in our belief for the ma-
jority of the readers sufficiently accurate way to
identify and select articles they are interested in.
The tables list and categorize all researched ar-
ticles. Pooling them over the several fields enables
the reader to reconstruct the content of a specific
paper. They furthermore act as a reference tool to
obtain the subset of papers that correspond to a
certain characteristic.
Each section clarifies the terminology if
needed and includes a brief discussion based on
a selection of appropriate articles. Plots are pro-
vided for a selection of characteristics to point out
the trends set by the research community. It should
be noted that the percentages are calculated in re-
lation to the total amount of technical papers. Also
note that some fields are not interpretable for some
methods and even though rare, some articles con-
tain more than one single method. Moreover, the
values for each year in the plots represent the aver-
age of the previous, the current and the next year.
Using this moving average allows to spot larger
research trends in an easier way. After all, a year
with fewer publications does not imply that the
topic has not been researched in that year.
Finally, in the last part (Sect. 3.8) we go one
step further and analyze the connection between
different classification fields. This provides in-
sights into research practices.
3.1 Patient Characteristics
Two major patient classes are considered in the lit-
erature: elective patients and non-elective patients.
The former class represents patients for whom the
surgery can be planned in advance, whereas the
latter class groups patients for whom a surgery is
unexpected and hence needs to be fitted into the

Frequently asked questions

Q1. What are the contributions in "Scheduling operating rooms: achievements, challenges and pitfalls" ?

This can be greatly supported by using advanced methods that are discussed in the academic literature. In order to help researchers and practitioners to select new relevant articles, the authors classify the recent OR planning and scheduling literature into tables using patient type, used performance measures, decisions made, OR supporting units, uncertainty, research methodology and testing phase. Furthermore, the authors see that important information that would allow readers to determine whether the reported research results are relevant to them is often missing. In order to avoid these pitfalls, the authors conclude that researchers need to state whether they target researchers or practitioners, motivate the choice of the used performance measures and mention both setting and method specific assumptions. Additionally, the authors identify promising practices and trends and recognize common pitfalls when researching OR scheduling. 

Q2. What have the authors stated for future works in "Scheduling operating rooms: achievements, challenges and pitfalls" ?

The authors classified the OR planning and scheduling literature over the years 2000-2014 with regard to the patient type, the different performance measures, the decision that has to be made, the integration of OR supporting units, the incorporation of uncertainty, the operations research methodology and the testing phase. For example, generally articles where analytical methods ( e. g., Markov models ) are used, will often assume estimated durations to be equal, as this is a strong assumption one should be careful when generalizing the results of these methods to inpatient scheduling. 

Q3. What are the common types of PMs used in the DES literature?

For instance, PMs that are mostly used in the DES literature are patient waiting time, overutilization, utilization, throughput and deferral. 

Q4. What is the common assumption used to solve the patient-to-date assignment problem?

An assumption that is typically made when using an MP or an improvement heuristic to solve the patient-to-date assignment problem is that the patient population that needs to be scheduled is known in advance (i.e., at the moment of scheduling). 

Q5. What is the reason for the lack of use of dynamic scheduling methods in the surgery scheduling literature?

the methods that are used for dynamic scheduling in an appointment setting are not easily transferable to a surgery scheduling setting for various modeling reasons (e.g., estimated slot durations in the former setting are assumed to be of equal length, while in the latter they are highly variable). 

Q6. What is the role of rescheduling in hospitals?

Research is needed on applicable rescheduling policies since it is an important mechanism in hospitals which affects both patient and staff satisfaction.