cases should total less than 45 mins per eight-hour or day in well functioning or suites. facilities with long work days will have greater tardiness because the longer the day, the more uncertainty about case start times. having patients’ medical records ready to go with all needed documents is essential for on time starts. case cancellation rate on day of surgery cancellation rates vary among facilities, depending partly on the types of patients receiving care, ranging from 4.6% for outpatients, to 13% -18% at va medical centers. recently published data from the uk estimate that 1 in 10 patients presenting for inpatient surgery have experienced a previous cancellation for their procedure, and that 1 in 7 patients being operated on had their procedure cancelled during a 1-week period in march 2017 in the uk national health service (nhs). many cancellations are due to non-medical problems such as a full icu, surgeon unavailability, or bad weather. or cancellation rates can be monitored statistically. well functioning or suites should have cancellation rates less than 5%. monitoring the cancellations correctly is calculated by taking the ratio of the number of cancellations to the number of scheduled cases. pacu admission delays pacu admission delays can be expressed as a % of workdays with at least one delay of 10 mins or greater in pacu admission because pacu is full. it is important to adjust pacu nurse staffing around the times of or admissions. algorithms exist that use the number of available nursing hours to find the staffing solution with the fewest understaffed days. contribution margin per or hour an or suite that puts up with excessive surgical times can schedule itself efficiently but still lose its financial shirt if many surgeons are slow, use too many instruments, or expensive implants, etc. these are all measured by the contribution margin per or hr. the contribution margin per hour of or time is the hospital revenue generated by a surgical case, less all the hospitalization variable labor and supply costs. variable costs, such as implants, vary directly with the volume of cases performed. this is because fee-for-service hospitals have a positive contribution margin for almost all elective cases mostly due to a large percentage of or costs being fixed. for usa hospitals not on a fixed annual budget, contribution margin per or hour averages one to two thousand usd per or hour. turnover times turnover time is the time from when one patient exits an or until the next patient enters the same or. turnover times include cleanup times and setup times, but not delays between cases. based on data collected at 31 usa hospitals, turnover times at the best performing or suites average less than 25 mins. cost reduction from reducing turnover times (because or workload is less) can only be achieved if or allocations and staffing are reduced. despite this, turnover time receives much attention from or managers because it is a key satisfier for surgeons. sometimes the or suite reduces turnover times (by providing more staff to clean the room for example) but new problems arise (not enough time for sterilizing instruments for the new case, can't bring patient to pacu because no beds) that were “hidden” by long turnover times. times between cases that are longer than a defined interval (e.g., 1 hr because to follow surgeon is unavailable) should be considered delays, not turnovers. prediction bias prediction bias in case duration are expressed as estimates per 8 hr of or time. prediction error equals the actual duration of the new case minus the estimated duration of the new case. bias indicates whether the estimate is consistently too high or consistently too low, and precision reflects the magnitudes of the errors of the estimates. efficient or suites should aim to have bias in case duration estimates per 8 hr of or time that is less than 15 minutes. a reason for bias can be surgeons’ consistently shortening their case duration estimates because they have too little or time allocated and need to “fit” their list of cases into the or time they do have. in contrast, other or suites may have surgeons that purposely overestimate case durations to keep control/access of their allocated or time so that if a new case appears their or time was not given away. remember that lack of historical case duration data for scheduled procedures is an important cause of inaccuracy in predicting case duration. in general, half of the cases scheduled in your or suite tomorrow will have less than five previous cases of the same procedure type and same surgeon during the preceding year. it would be nice to have no uncertainty in case duration prediction. but, it is present. the problem is looking for a single number that is correct most of the time. you won't get accurate estimates by using historical case duration data. rather, from the historical data you'll get an assessment of the uncertainty. prolonged turnovers times between cases that are longer than a defined interval. (note: late arrival of a surgeon should be considered delays, not turnovers.) operating room productivity operating room productivity is the quantity and quality of output (typically surgical cases) from the surgical suite in contrast to the amount of input required (such as physicians and nurses and equipment for example). many institutions believe that productivity (output/input) can be accomplished without sacrificing convenience (rapid access to open or time such that a surgeon can book a case without having to wait) but these two aspects are not separable. typically, the greater the operating room utilization, the less the convenience (able to book cases when desired) as defined by surgeons and patients. this is because as utilization goes up there is less available open staffed or time available on short notice. in other words, the greater the access and convenience, the lower is operating room utilization (because of the need for extra capacity), at least as perceived by hospitals and anesthesiologists. this high level of customer service of being able to book cases on short notice is one reason ambulatory surgery centers typically have lower or utilization than big city hospitals. the outpatient surgery center usually has reduced overhead when compared to a big city hospital, and therefore can financially get away with lower or use. sociopolitical factors in management of the surgery suite: "or equilibrium" management of the operating room suite must acknowledge that people are the primary resource. although management science theory may tend to hold constant the preferences and bias of the individuals working in and utilizing the surgery suite, management of the surgical suite with regards to case scheduling is strongly influenced by personal, political, and economic relationships within an institution. who is the main customer of your surgical suite? to best align management goals with institutional objectives the or director needs to identify the primary customer of the surgical suite. an or can be completely balanced or it can be biased to one or more its constituents. the main people to consider are surgeons, anesthesiologists, nurses, the hospital (upper management), and of course the patient. a first step is to determine whose preferences or workload dominates the surgical suite. if surgeons are in large demand with small supply, then that may outweigh other interests. for example, a private facility may have surgeons who can pull their patients to another hospital if made to wait. as another example, in a private surgeon-owned surgery center, management may be directed as maintaining a particular partner's workload and the incentives are to schedule his/her cases with priority. the same supply/demand balance applies to anesthesia. the situation may exist where a specific surgery group will only work with its contracted anesthesia group. in this case, a manager may have to wait until the contracted anesthesiologist is ready for the case, even if this means idle or time. this can be avoided in institutions where one group has exclusive rights and controls anesthesia privilege over all the ors. this arrangement is seen commonly because it eliminates factions and streamlines anesthesia placement for cases, either elective or emergency. hospital (upper management) run ors are identified by those facilities where the hospital executives acting as agents for government authorities determine staffing and workload. examples include hospitals in public health care systems like in european countries or the va united states department of veteran affairs in the usa. in other surgical suites, in contrast, management decisions have patients as the first priority. facilities performing elective cosmetic procedures for cash reimbursement are an example. due to the patient being able to choose where they have plastic surgery, patients expect special circumstances such as first-rate customer service. additionally, if a patient is one hour late for surgery the patient will most likely still be able to undergo surgery. this concept is in contrast to a large academic hospital, for example, where a patient who misses their check-in window for elective surgery is often removed from the surgery schedule to make room for re-shuffled elective and emergency cases. what are the preferences of the main customer in the surgical suite? once the manager has identified the critical few customers and the necessary many customers, then the next step is to determine their preferences and incentives. surgeons will favor early block surgery times, rapid turnover, low cancellation rates, and on time starts. the hospital (upper management) will want the most surgical output with the least associated cost. patients will likely favor reduced waiting times for surgery start. finally, nurse managers and anesthesiologists will be inclined to high operating room utilization, minimal overtime, the flexibility to move cases around, and reserve capacity in the ors. much like economic game theory, agents in the or will position their interests in a nature as to maximize their returns. it is up to the or manager to weigh the contributions of each agent and provide enough or time and resources to maximize the output of the surgical suite in its entirety. theory and applications of operating room management this discussion addresses capitalistic healthcare markets. a discussion of socialized medicine would include several other factors which influence the supply and demand for surgical care. analysis of operating room management within socialized medicine is becoming increasingly frequent in the medical literature, but is beyond the scope of this article. a manager must select benchmarks in order to analyze changes from baseline operations. upgrades to existing operating infrastructures should be demonstrated as efficiency gained compared to baseline practices. management criteria must therefore include preoperative, intraoperative, and immediate postoperative system analysis. preoperative management issues waiting time and operating room scheduling are the two key preoperative determinates. waiting time prior to operation the time from surgical scheduling to check-in for the procedure is defined, for these purposes, as “preoperative wait time.” use of a surgical suite depends greatly on, and increases as, the average length of time patients wait for surgery increases. as waiting time increases, more surgical dates (blocks) can be evaluated for a good match between a case's duration and the open times in the blocks. in some communities, competition among surgeons and hospitals may not allow the average length of time that patients have to wait for surgery to be as long as 2 weeks. an or suite then cannot expect block time utilization from elective cases to exceed 90%, assuming that enough block time is allocated for a surgeon to complete all of the elective cases in the block time. for these purposes, wait time can be equated to the price of an object. the price for an object increases if demand increases and/or supply reduces for that object. hence, “preoperative wait time” will increase as demand for surgery increases and/or surgical supply (operating room availability) reduces or fails to grow proportionally to surgical demand. by accurately gauging a patient population and an operative facility's capacity, an effective manager can minimize the wait for elective and imminent procedures while covering all emergency cases and without overextending the operative team. scheduling operating room calendars case scheduling or correctly selecting the day on which to do each elective case so as to best fill the allocated hours is most important, much more so than, for example, correcting errors in predicting how long elective or add-on cases would last, reducing variability in