Designing the Sterile Processing Department

December 1, 2002

Designing the Sterile Processing Department

Designing the Sterile Processing Department

By Felipe Mejia

When contemplating the design of a central service processing area, location-- of the department, areas within the department, and equipment -- becomes aprimary consideration. The first step should be defining the function of sterileprocessing and what is required to accomplish that function. The goal is tocreate an efficient infrastructure to support the processing of instruments andsupplies for the operating room (OR).

The design criteria will depend on the needs of the OR, such as the number ofoperating suites, expected use, the type of cases that will be performed and thedistance between OR and sterile processing. Armed with this information, you canassess the type and quantity of equipment needed to wash the soiled goods;specifically, the number of washers, automated or manual, size, type and numberof cart washers, if any.

The next step is the selection of fixtures and support equipment for thedecontam area. The type and number of washers will dictate the number of sinks,washer-ultrasonics, hoppers, etc. Moving on to the clean side, again, based onthe number of washers, it is possible to determine the number and type ofsteam-sterilizers, gas-sterilizers, plasma sterilizers and other equipment. Thenumber of washers and sterilizers will determine the number of workstations forprep and pack.

Once the amount of equipment, fixtures and stations has been defined, thenumber of full time employees (FTEs) can be established. This number willdictate the additional rooms needed to support staff, such as restrooms,employee lounge and manager's office. The size and type of equipment will alsodefine the mechanical space needed for service support equipment. Finally, it'stime to put the puzzle together. The goal is to minimize cross-traffic, allowenough space for people to work comfortably and minimize travel time in betweenpoints of activity.

Washer Selection

The key to determining the number of washers is assessing a theoreticalaverage number of trays and basins per procedure and the average number ofprocedures per day. For example, if a hospital has six OR suites and expects toturn each OR suite over every three hours, based on the type of cases it expectsto receive, it estimates an average of 12 trays and eight basins per procedure.This means they will need to wash a total of 72 trays and a combination of 48basins and containers in a three-hour period.

Suppose the hospital considers a standard stand-alone, single-chamber washercapable of processing eight trays or eight large basins per one-hour cycleincluding the time it takes to load and unload; 72 trays can be processed innine cycles and 48 basins can be processed in six cycles. Therefore they mustcomplete 15 cycles in order to wash all the soiled items received in athree-hour period. One washer can complete three cycles in the three-hourperiod; therefore, five washers working at full capacity are needed to completethe task.

An alternative is a tunnel washer. Tunnel washers have a higher throughputthan a single washer. However, the instruments will require more preparation(pre-wash), which means more FTEs. Another consideration with tunnel washers isthat if there is a mechanical problem the entire washing comes to a halt. If asingle chamber washer is down, with five washers the throughput will still be 80percent.

Another alternative is to automate the single-chamber washers. Withautomation, the loading and unloading is more efficient. The total time perwasher is reduced to the cycle time of the washer since the racks with the trayscan be queued. In the example above, a typical fully automated system (queuing,auto loading, auto unloading and rack return) would reduce the washing time toabout 40 minutes. Three to four washers can do the work of five washers in thesame time. Selecting four will introduce a time cushion unavailable before. Inaddition, the number of FTEs can be reduced because once the trays are queued,the employees are free to do other tasks. Generally, a typical twosingle-chamber, fully-automated system will have the same throughput as a tunnelwasher and occupy the same footprint area.

Independent of the number or type of washing system selected, it is wise toallow space for future expansion if at all possible. Save the space for an extrawasher, for example. There may be extra space on the decontam side for a while,but if the hospital grows it will not incur tremendous remodeling costs byadding a washer.

Fixtures and Equipment in the Decontam Area

Plan for a hopper near the entrance to the decontam area. The nextrequirement is a sink-station with multiple sinks and counter space to unloadsoiled items in need of pre-wash. In addition, a number of ultrasonic cleanersmay be required.

The number of sinks and the size and number of ultrasonic washers will bedetermined by the type and the number of washers. For example, a washer thatcirculates a high volume of water at a low pressure is more efficient and hardlyrequires any pre-washing. A two to six single-chamber, fully automated systemwill only require one sink station and one small ultrasonic cleaner.High-pressure, low-volume washers and tunnel washers will require twice thenumber of sinks and ultrasonic cleaners. Some tunnel washers are equipped withan ultrasonic chamber.

Cart Washer

The key in determining the size and number of cart washers needed is toestimate the average number of carts per surgical procedure. Continuing with theexample above, let's assume that the hospital estimates that every procedurewill yield three 36-inch soiled carts. This represents 18 soiled carts everythree hours or six carts per hour.

Options include wiping the carts manually, assuming that it will take no morethan 10 minutes to wash and dry a cart. If this option is chosen, a washing roomwith a spray gun is recommended. The cost of this option will be mostly labor,water and chemicals.

A cart washer will do a more thorough job. When selecting a cart washer it isnecessary to look at the net usable dimensions and cycle time. Generally, therecommendation is to use the largest cart washer that will fit in the area asthe cycle time will be the same and the price difference and the utilityconsumption are normally insignificant compared to the benefits of a higherthroughput.

Consider a cart washer that has a cycle time of 10 minutes. This means athroughput of six carts per hour if it accommodates one cart. However, if weselect a cart washer with larger net usable dimensions that will process twocarts per cycle, it is possible to wash the same number of carts in half thetime. The extra half-hour that is gained will become particularly useful duringpeak periods and when the cart washer needs servicing. In addition, basins andcontainers can be washed through the cart washer, reducing the load on thewashers. Revisiting the example above, if all the basins are washed through thecart washer, the fully automated washing system can be reduced to three washerssince we are reducing two cycles per hour.

Felipe Mejia is a design engineer for Belimed USA and is a member of theAmerican Society for Healthcare Central Service Professionals (ASHCSP).