How Many ORs? It’s Complicated

Surgery SuitePlanning a surgery suite used to be fairly simple. General operating rooms were used for a wide range of procedures and dedicated operating rooms were limited to cardiac surgery and orthopedics. At the same time, interventional radiologists and cardiologists created their own workplaces. Today, planning surgical and endovascular suites is complicated by the convergence of diagnostic imaging and surgical procedures, rapidly changing technology, increasing specialization, and strict distinctions between operating rooms and procedure rooms. From a facility planning perspective, the number, size, and specialization of ORs and endovascular procedure rooms is the single most significant factor contributing to the overall footprint of the suite (and project cost). Moreover, the numbers and sizes of related patient care and support spaces are driven by the number and types of operating/procedure rooms. More importantly, the number of operating/procedure rooms drives ongoing staffing and related operational costs.

It is commonly understood that invasive procedures must be performed in an operating room. ORs are designed to provide a safe environment for procedures that carry a high risk of infection, and any form of anesthetic may be administered in an OR. On the other hand, confusion arises because the level of invasiveness of medical procedures falls along a spectrum between noninvasive and invasive. Procedure rooms are used for procedures that do not require an aseptic field and where there is no cutting of the mucous membranes even though sterile instruments and supplies may be used. Local anesthesia, or minimal or moderate sedation, may be administered in a procedure room.


As imaging procedures become more interventional and no longer limited to diagnostic uses, surgery is becoming less invasive. With the melding of interventional radiology and minimally-invasive, image-guided, and traditional open surgical techniques, the FGI Guidelines have established three classification levels for imaging rooms to reflect different levels of patient acuity and intervention. Most conventional diagnostic imaging rooms are categorized as Class 1. Procedure rooms where minimally-invasive or percutaneous interventional procedures are performed on patients under moderate sedation or general anesthesia would be Class 2. In this classification system, a hybrid OR is a Class 3 imaging room because it supports open surgical procedures and general anesthesia. This classification system dictates the minimum clearances, room size, design details, environmental controls and other infrastructure requirements, and room location within the surgical/endovascular procedure suite.


Hybrid ORs combine the requirements of an operating room and an imaging room and are typically characterized by the type of imaging equipment installed in the room and the clinical services offered. Standard imaging equipment installed in a hybrid OR includes single-plane or biplane angiography equipment and CT and MRI scanners. Single-plane systems are the most common, and they are used for an array of cardiac and vascular procedures. The multi-axial robotic angiography system is a single-plane system with eight rotational axes that provide more images at different angles without using biplane technology. It provides images similar to a CT scan but offers more flexibility. These systems may be mounted on the floor or ceiling. Biplane systems can acquire images from two reference points at the same time. They have two C-arms — one mounted on the floor and one on tracks in the ceiling. These systems are required for neurosurgical cerebral endovascular procedures.


Whether planning a traditional surgery suite or an integrated surgery and endovascular procedure area, the process begins with determining the number of procedure rooms — surgical operating rooms, endovascular procedure rooms, and hybrid rooms. Some healthcare organizations may have already settled on the number and type of operating/procedure rooms based on a detailed business plan (What can we afford?). Also, partnerships with equipment vendors, or the existence of an enthusiastic donor, may result in early agreement on one or more hybrid or specialty procedure rooms regardless of the current workload.

As a first step, specialties requiring unique space or fixed equipment must be identified. These specialties typically include cardiovascular surgery, neurosurgery, orthopedics, gastrointestinal/genitourinary (GI/GU), and gynecology. Many other procedures can be accommodated in the same flexible OR or procedure room. Ideally, the number of dedicated rooms should be kept to a minimum.

Next, the projected annual cases/procedures and annual minutes should be tabulated by specialty and patient type (inpatient, same-day admit, and outpatient), and sorted by the type of procedure room required. The average minutes per procedure, or room time, can be calculated for each specialty by dividing the annual minutes by the annual number of procedures. Hospitals also typically record the average room turnaround time, which is the time between when one patient leaves the procedure room and the room is ready for the next patient. Throughput is the rate of patient flow through the OR or procedure room — such as 2.5 cases per OR per day, or 900 annual cases per OR.


In an integrated surgical and endovascular procedure suite, optimal flexibility could be achieved if all the procedure rooms were interchangeable. However, the physical configuration and patient and staff flow for an OR and an endovascular procedure room are different. ORs are typically designed with dual access to the procedure room — one from a perimeter corridor for the patient and staff and the other from a central clean core area from which case carts and other sterile supplies and equipment are placed in the operating room. An endovascular procedure room is configured with an adjacent control room with staff workstations and a contiguous system component room rather than a clean core area. These rooms also require radiation protection. The difficulty in projecting future workload comes when procedures performed in an OR or endovascular procedure room today are expected to migrate to a hybrid operating room. Also, new and often experimental technology may involve longer procedure times, thus initially reducing the number of procedures to be accommodated in a specific room.

Note: Detailed calculations for determining the number of operating rooms, endovascular, and various other procedure rooms can be found in the SpaceMed Guide.

See related post: Factors Affecting the Size of the Surgery Suite.

This article is an update of a previous post.