Use and management of double-door ethylene oxide sterilizer
1. Properties and sterilization principle of ethylene oxide (EO)
1. Properties and sterilization principle of EO
EO gas can undergo non-specific alkylation reaction with carboxyl, amino, sulfhydryl and hydroxyl groups on microbial proteins, thereby interfering with their various physiological functions and finally leading to the death of microorganisms. It can kill bacterial propagules and spores, fungi and viruses. EO has the advantages of strong penetration, wide bactericidal spectrum, little damage to items, and reliable sterilization effect. It is widely used in medical supplies, especially for sterilization of precision instruments, catheters, implants, surgical instruments, etc. that are not resistant to high temperature, high pressure and easy to corrode. However, EO has certain toxicity. After sterilization, the items need to be ventilated and exposed for a long time to completely dissipate the absorbed EO before they can be used clinically.
2. Advantages of sterilization system
3M double-door EO sterilizer has a high degree of automation, built-in data printer, synchronously records important parameters in the entire sterilization cycle, can automatically vacuum, automatically add drugs, automatically adjust temperature and humidity, and automatically control sterilization time and analysis time. The entire sterilization process can be observed on the display screens on both sides of the sterilizer. If a fault occurs, the machine will immediately alarm and display the fault code. During the EO sterilization process, the furnace chamber always maintains a negative pressure state to ensure that EO does not overflow. During sterilization, if EO leaks, the machine will immediately alarm and stop the sterilization process. The double-door EO disinfection cabinet introduced by our hospital is also advanced in that it is a double-door design that can strictly separate the clean area from the clean area, which is conducive to the rational and orderly circulation of items.
3 Experience in the use and management of sterilization cabinets
3.1 Preparation work
3.1.1 Cleaning and packaging Items sterilized with E0 must be thoroughly cleaned, and be careful not to wash with saline. Because after washing with saline, microorganisms are wrapped in crystal lattices and are not easily killed by EO. There should be no water droplets or too much water on the items to be sterilized to avoid dilution and hydrolysis of EO. When receiving the sterilized items sent by various departments, a senior nurse with a strong sense of responsibility must be assigned to receive, register and sign. Because most of the items sterilized with EO are expensive precision instruments and implanted catheters, they need to be carefully classified and packaged. Usually, we take the department as the unit, put the clean items to be sterilized into paper-plastic packaging bags, seal them with a sealing machine, write the department name, and record the quantity to prevent mistakes.
3.1.2 After the loading items are ready, they should be loaded in order according to the nature of the items. First, tilt the classified and packaged items into the double-layer metal grid of the sterilizer, leave gaps between the items, and the sterilized items cannot touch the cabinet wall. For paper-plastic composite materials, be sure to place them in the order of paper surface to plastic surface. The amount of items loaded in the sterilizer should not exceed 80% of the total volume of the cabinet, because if the amount of items loaded is too much, the amount of EO gas absorbed by the items will increase, causing the pressure in the cabinet to drop, the machine alarm, and it cannot operate normally. At the same time, the effective concentration of EO gas in the cabinet is insufficient, which will lead to sterilization failure.
3.1.3 Correctly select the sterilization temperature. General items are sterilized at 55℃, but items that cannot tolerate 55℃ should be sterilized at 37℃. This can not only ensure that the performance, structure and quality of the sterilized items are not damaged, but also ensure the sterilization effect.
3.1.4 Correctly select the desorption time of sterilized items. Contact with excessive EO residues can cause burns and irritation to patients. The amount of EO residue is related to the material of the sterilized items, sterilization parameters, packaging materials and packaging size, loading capacity, desorption parameters, etc. Desorption means that the items sterilized by EO must be used after the adsorbed EO and its by-product residues are dispersed. This depends on the nature of the items. For example, metal and glass can be used immediately after the sterilization procedure is completed, but some materials require a longer desorption time, such as built-in pacemakers, dialysis tubes, etc., which require desorption for more than 12 hours.
3.2 Observation of the sterilization process
The ethylene oxide sterilization procedure includes preheating, prehumidification, vacuuming, introducing gasified ethylene oxide to reach a predetermined concentration, maintaining the sterilization time, removing the ethylene oxide gas in the sterilizer, and desorption to remove the EO residue in the sterilized items. The above steps are indispensable. When performing E0 sterilization, the operator must frequently check the computer display screen. If the machine alarm is found, and a fault code appears, the corresponding processing should be carried out immediately: (1) If the machine alarm code appears C¡-C₂, it means that the sterilizer will not stop running, but if it is not processed, it will affect the sterilization effect. The operator must eliminate the fault according to the processing method in the search table, and the code will automatically disappear. (2) If the machine fault code E-E₂ appears during the self-test stage, it means that the sterilizer cannot start running. It must be eliminated according to the processing method in the search table, and the code will automatically disappear and the sterilizer will start running. (3) If the machine displays fault code E₂-E„ during the preparation stage, it means that the sterilizer stops running before the gas is released and the items are not sterilized. At this time, the operator should first open the furnace door, then press the "stop" button, and then restart the sterilizer after troubleshooting according to the processing method in the search table. (4) If the machine displays fault code E.-E„ during the sterilization stage, it means that EO gas has been released. If any of the sterilization parameters: temperature, humidity, and EO gas concentration does not meet the sterilization standard, the machine will alarm to indicate that the items have not been sterilized. At this time, the released EO gas automatically enters the final exhaust and air washing stage, which takes 45 minutes.
Note that troubleshooting at this stage must be performed by professional engineers.
3.3 Sterilization effect monitoring
Ethylene oxide gas sterilization must be carried out for process monitoring of each pot, chemical monitoring of each package, and biological monitoring every month. Only when the sterilization process meets the requirements and the chemical indicator meets the specified standard color requirements can it be issued. After long-term observation, the color change of the chemical indicator card will vary depending on the temperature selected for sterilization. The green color of the chemical indicator card changes to darker when sterilized at 55℃ than when sterilized at 37℃. After sterilization, whether the chemical indicator card changes to dark green or light green, it is qualified after our synchronous biological monitoring.
3.4 Safety Management
EO gas is harmful to the human body. Excessive inhalation can cause acute poisoning phenomena such as vomiting and impaired consciousness. Skin contact with EO liquid can cause burns or frostbite. The threshold for people to smell E0 is 700ppm, and the allowable concentration of EO in the working environment should be less than 1ppm, so safety protection must be taken seriously during use.
3.4.1EO should be kept and properly stored by a designated person. EO cylinders should be stored in a cool, ventilated place without fire sources and power switches. When using, they should be handled with care and avoid violent collisions. The storage cabinet should be locked to prevent loss.
3.4.2 Operators should wear masks and gloves during E0 sterilization. When the operator is unloading, excessive contact with the degradation products and residues of EO can cause eye irritation. In order to reduce the chance of direct contact, the furnace door should be opened for about 5 minutes to allow fresh air outside the cabinet to be replenished into the cabinet room, and the sterilized items should be unloaded quickly. After unloading, try to reduce the number of times the sterilized items are sorted and turned. When transferring sterilized items, people should stand in the leeward direction to operate.
3.4.3 Excessive contact with EO gas can cause respiratory irritation, nausea, vomiting, dizziness and neurotoxic reactions. If this happens, leave the scene immediately, rest in a well-ventilated place, breathe fresh air, and seek medical attention as soon as possible.
3.4.4 Regularly test the working environment and the amount of ethylene oxide remaining in the sterilized items. If abnormalities are found, report them in time and deal with them urgently. With the development of modern medical minimally invasive surgery and microsurgery, and the application of polymer materials, ethylene oxide sterilization is becoming more and more widely used in hospitals. Scientific and standardized operation of double-door EO sterilizers and strict control of sterilization parameters are the key to ensuring the quality of EO sterilization.
