The Economics of Autoclave-Based Sterilization: Experience from Central Sterile Supply Department of a Cancer Center in Eastern India

To the Editor—The central sterile supply department (CSSD) is an essential component of hospital services. Sterilization of a wide range of materials is required for therapeutic, diagnostic, and infection control applications. ^{1 , 2} Depending upon the nature of materials and infrastructure available, these items are sterilized using autoclaves (steam sterilizers), ethylene oxide (ETO) sterilizers, or vaporized hydrogen peroxide (plasma) sterilizers. ¹ Our CSSD in the 183-bed oncology center in eastern India is equipped with 3 autoclaves (Tuttnauer, Israel). The actual cost of autoclave-based sterilization is not readily available. ^{3 – 7} The purpose of this retrospective study was to document the cost of autoclave-based sterilization by the CSSD at our hospital. The results of this study are useful in cost rationalization, patient billing and the assessment of quality control costs.

Autoclaving cost was calculated by taking into account equipment capital cost, laundry cost, water cost, electricity cost, consumable costs (of sterilization indicators, packaging materials, and instrument cleaning solutions), human resource cost, depreciation cost of equipment, and cost of equipment maintenance contracts. The cost of making 1 L single reverse-osmosis (RO) water was Indian rupees (INR) 0.20 (US$0.003) and the cost of making 1 L double-RO water was INR 0.40 (US$0.006). The cost of electricity included the electricity requirements of the washer disinfector system (heater and pump), the thermal drying cabinet, the autoclave (steam generator and pump), and the electricity used for general purposes such as lighting and air conditioning inside the CSSD. The total electricity cost was calculated using a cost of INR 10 (US$0.17) for 1 kWh (Table 1). The total cost associated with the autoclave was INR 6,077,977 (USD 91,191) plus comprehensive maintenance contract of INR 200,000 (USD 3,000) per year. The cost per cycle of the autoclave was based on a total cycle calculation of 24,000 cycles: 8 cycles per day ×25 days per month ×12 months per year ×10 years. Depreciation cost was calculated using depreciation over 10 years for capital equipment (ie, steam sterilizers, washer disinfector, drying cabinet costs). Human resource cost was calculated for the total CSSD manpower cost per month for 1 scientific officer, 4 technologists, 7 attendants, and 2 housekeepers.

TABLE 1 Water and Electricity Consumption Details for Equipment Used for Surgical Sets

NOTE. RO, reverse osmosis; TDS, total dissolved solids.

^a For single-RO water, TDS content=80 ppm; for double-RO water, TDS content <10 ppm.

According to our sterilizer load analysis, most of the items in our hospital are steam sterilized: ~75% are steam sterilized; ~20% are ETO sterilized; and ~5% are plasma sterilized. ¹ In May 2015, for example, a total of 17,693 items were sterilized: 13,266 items were sterilized by autoclave, 3,674 items were sterilized using ETO, and 753 were sterilized using plasma. The materials sterilized by autoclave included surgical sets, minor procedure sets, linens (ie, surgical gowns and patient drapes) and dressing materials (ie, gauze and cotton). The total cost of sterilizing a surgical set was INR 374.07 (US$6.23) per unit, and the cost of sterilizing a minor procedure set was INR 81 (US$1.35) per unit (see Online Supplementary Table 2 online). Surgical instrument sets included laparotomy sets, gynecological cancer sets, urology general sets, head and neck sets, and plastic surgery sets. Instrument sets for minor procedures included wound-dressing sets, stitch-cutting sets, suturing sets, lumbar puncture sets, bone marrow sets, etc. We also calculated the linen re-sterilization cost for patient drape sets and surgical gown sets, which included the manufacturing cost of 1 sheet (estimated to be used 100 times), laundry cost, and similar cost categories.

Few details or data are available regarding CSSD costs; ^{3 – 7} however, costing information is crucial. A previous study published in Brazil showed that the cost for sterilization by autoclave was US$31.37 and that low-temperature steam and gaseous formaldehyde sterilization (LTSF) cost US$255.28. ⁶ The cost of surgical set sterilization in our center was considerably less than that mentioned in the Brazilian study. In our study, the cost of autoclave-based sterilization of minor procedure set was less than that for a surgical set for several reasons: (1) less receiving time per set, (2) fewer instruments in the minor procedure set, (3) no manual cleaning of the minor procedure set (eg, primary cleaning is done in the procedure area in outpatient departments), (4) less set assembly and packaging time compared with surgical procedure sets, and (5) easier loading and unloading than for surgical procedure sets.

The cost of utilities (water and electricity) was different for each type of sterilized product (eg, surgical set, minor procedure set, surgical gown set, and patient drape set) for several reasons. (1) Water and electricity consumption for the washer disinfector is 4 times less for minor procedure sets than for surgical procedure sets. (2) No manual cleaning is required for minor procedure sets. (3) Electricity consumption by the thermal drying cabinet is less for minor procedure sets. (4) Water and electricity consumption of steam sterilizer for minor procedure sets is half that needed for surgical procedure sets (Table 1). Depreciation costs of equipment included those of washer disinfectors, dryers, and steam sterilizers. Depreciation was calculated using the initial capital cost of equipment and the cost of comprehensive maintenance contract of equipment divided over 10 years.

For surgical sets and minor procedure sets, the major cost contribution was due to consumables followed by electricity; for surgical gown sets and patient drape sets, the major costs were the manufacturing cost of the gowns and drapes followed by the cost of electricity. Calculating the cost of autoclaved-based sterilization is essential to assessing costs, to making decisions about patient billing, and for monitoring the effect of quality control on cost.

These cost categories demonstrate that there are no shortcuts to sterilization. Optimizing various factors contributing to costs is an ongoing challenge facing quality control managers, CSSD managers, and hospital administrators.