So long as there are surgeons who arrive late, cases that run long, nurses who call out sick and ruptured abdominal aortic aneurysms that present at 9 a.m., there will be disruptions in your OR schedule. Yes, things don't always go as planned on the day of surgery.

You must schedule add-on cases. Fill gaps in the schedule. Move cases. Assign staff. Prioritize limited resources and personnel. Prepare patients. Sequence urgent cases. You must adjust on the fly, be comfortable with chaos and sometimes manage by the seat of your pants, by instinct or by intuition.

What if you could integrate decision-making on the day of surgery? After reading this article about OR management on the day of surgery, you'll better understand how to decide what cases to postpone, what cases to move and so forth in response to unforeseen changes in the OR schedule. The goal of all of this is to maximize OR efficiency and minimize patient waiting time.

I've drawn up seven scenarios that might take place in an outpatient surgical facility on the day of surgery, and employed scientific decision-making to provide solutions that maximize OR efficiency in each.

The scenarios are based on the following conditions. First, they involve elective cases scheduled well in advance of surgery, without urgent cases or a substantial add-on workload. Second, each case can be done in any of the ORs by any of the nursing and anesthesia staff members. Finally, the eight-hour workday for all ORs begins at 7 a.m. and ends at 3 p.m. Given these conditions, the definitions and statistical methods can be simplified markedly.

Scenario 1:
An admissions nurse calls in sick.
Everyone is hustling, but they've fallen a bit behind schedule. OR 1 and OR 2 both call for their next patients at 11 a.m. Both rooms are expected to be ready within 30 minutes, but realistically, either OR could be delayed an additional 15 minutes. The case in OR 1 is scheduled to begin at noon. OR 1 is running ahead of schedule, but would still have to wait for its patient. OR 2 is running behind schedule by about one hour. While OR 1 is expected to finish its cases by 4 p.m., OR 2's work is expected to conclude at 2 p.m. Which OR should be served first?

Solution: Reducing overutilized OR time - the time an OR is occupied beyond its allocated eight-hour workday - and its associated labor costs should be a higher priority than reducing how long surgeons and patients wait past scheduled start times. Staff members should focus first on readying a patient for OR 1.

Scenario 2:
An anesthesiologist is medically directing CRNAs in two ORs with caseloads of pediatric patients.
For the first cases of the day, both ORs will have mask inductions followed by IV placement. OR 3 has eight 45-minute cases scheduled. OR 4 has two three-hour cases. Each OR has one surgeon doing all of the cases. Both ORs are ready to go. Overutilized OR time is not expected in either. Which of the two ORs should the anesthesiologist start first?

Solution: Since overutilized OR time - the deciding factor in Scenario 1 - is not expected, the decision should be based on reducing the amount of time that patients wait beyond their scheduled start times. If procedures occupy an extra 10 minutes, for instance, OR 3's total patient waiting time would increase to 70 minutes (seven patients multiplied by 10 extra minutes each). OR 4's total waiting time, on the other hand, would be 10 minutes (one patient multiplied by 10 minutes). The anesthesiologist should begin OR 3 first.

Scenario 3:
An anesthesiologist is supervising resident physicians in OR 1 and OR 2.
Allocated OR time is from 7 a.m. to 3 p.m. These ORs have just finished their first cases. The last case of the day in OR 1 is scheduled to be finished at 2:30 p.m. The last case of the day in OR 2 is scheduled to be finished at 4:30 p.m. Which OR should the anesthesiologist start next?

Solution: OR 1 is expected to have no overutilized hours. OR 2 is expected to have 1.5 overutilized hours. If the patient for OR 2 is ready, the anesthesiologist should start OR 2 first.

Scenario 4:
When an OR is finished with a case, nurses use an intercom system to notify the housekeeping staff that it is ready for cleaning.
Only one housekeeper is available when the intercom announces, "Done in OR 1." Moments later, the intercom sounds again: "Done in OR 2." If the cases in OR 1 are expected to be done around 3:30 p.m. and those in OR 2 by 1 p.m., which OR should the housekeeper clean first?

Solution: The answer depends on the possibility of overutilized OR time which, as I've explained, is the higher priority. The housekeeper should focus on OR 1 first in order to reduce overutilized OR time.

Scenario 5:
A surgeon is scheduling two cases for an afternoon. There are no medical reasons why one must be performed before the other.
Patient A's procedure is likely to take 45 minutes. Realistically, its duration will not be less than 30 minutes or more than one hour. Patient B's procedure is likely to take two hours and 30 minutes. Its duration may be as little as one hour, 45 minutes, or as long as three hours, 30 minutes. Which patient's procedure should be scheduled first?

Solution: Since one procedure will be done directly following the other, overutilized OR time is not a consideration. Instead, the choice revolves around patients waiting past their scheduled start times. If Patient A's shorter, more predictable case were first, Patient B would have to wait 15 minutes at most. If Patient B's longer, less predictable case were first, Patient A might have to wait as long as one hour. Patient A's case should be performed first.

Scenario 6:
A pathology technician and pathologist are on site.
Two ORs have frozen sections for them to review at the same time. While the pathology team will work diligently for both ORs, they have to choose one OR's sections to review first. Excluding pathology delays, OR 3 is expected to finish at 3:45 p.m. and OR 4 at 1 p.m. Which OR should the pathology team assist first?

Solution: The focus should be on reducing overutilized OR time. Even with no delays, OR 3's procedure can be expected to occupy 45 minutes of overutilized time, since the workday ends at 3 p.m. As a result, the pathology team should work on OR 3's specimens first.

Scenario 7:
Only one nurse is currently available to retrieve supplies from the sterile area.
In OR 1, a surgical team is setting up equipment while anesthesia induces the patient. They call for supplies. Moments later, surgery in OR 2 is temporarily halted due to a broken instrument. OR 2's team calls for supplies second, stat, because the surgeon is scrubbed and frustrated.

Excluding the time it takes to fill the requests, OR 1's current case is expected to end at 1 p.m. and OR 2's at 1:45 p.m. OR 1's case started 30 minutes early and the surgeon has one patient to follow. OR 2's case started 25 minutes late; the surgeon has three patients to follow. No overutilized OR time is expected in either room.

Solution: Focusing on OR 2 would reduce the total amount of time patients wait past their scheduled start times, so the nurse in the sterile area should deliver OR 2's supplies first.

Imperfect science
The science of decision-making tends to be highly technical because its objective is not simply to show a rational way to do something. Rather, it is to prove mathematically that one particular way is better than any other.

In December, my colleagues and I published an article in Anesthesiology discussing decision-making on the day of surgery (see "Decision-making: The Four Priorities"). We demonstrated how the scientific methods of decision-making apply comprehensively to OR management's operational issues. Factors such as advance scheduling and sequencing of cases, accounting for delays, and allocating and releasing OR time can all be considered mathematically. The science of decision-making to OR management can't, of course, pacify surgeons' and staff members' frustrations with working later than planned, and there will always be unexpected disruptions and delays in OR caseloads.

However, the scenarios and principles described above may offer a better understanding of how to address the decisions involved in the day-to-day operation of your facility.

Remember, the schedule drives everything that happens in the OR, but the schedule depends on many subsystems such as staffing, the availability of supplies and equipment. A poorly run schedule can lead to bottlenecks, frustrating not only patients and families but physicians, staff and nursing units.