Thermal sterilization
These methods are considered the most reliable and are used for heat-resistant items.
1. Steam sterilizer (autoclave) Processing is carried out using saturated water steam under pressure. The device has a double-walled design with a pressure gauge and thermometer. Items are placed inside in packaging or special boxes—drums (bixes). During the cycle, the vents of the drums must be open for steam access, and they are closed immediately after unloading.
- Mode for instruments and syringes: pressure 2 atm (132.9 °C), time — 20 minutes.
- Mode for rubber items (gloves, drains): gentle pressure 1.1 atm (120 °C) for 45 minutes.
Safety precautions: Timekeeping starts strictly from the moment the set pressure is reached on the pressure gauge. Opening the lid is allowed only when the pressure drops to zero.
2. Dry-heat cabinet The device sterilizes with dry hot air. Suitable for metal and glass. First, items are dried with the door open (30 minutes at 80–85 °C). Then the cabinet is hermetically sealed and sterilization is performed: 60 minutes at 180 °C. Instruments can be removed only after the chamber cools down to 70–50 °C. The equipment requires mandatory grounding.
Boiling (auxiliary method)
Used in facilities that do not have a central sterilization department (CSD). Instruments are placed in a boiler with distilled water.
- Standard mode: To increase the boiling point and destroy bacterial membranes, sodium bicarbonate (2% solution) is added to the water. Standard instruments are boiled for 40 minutes.
- Syringes and needles: Boiled for 45 minutes in pure water without adding soda.
- Specific contamination: Instruments after contact with pus or feces are boiled separately for 90 minutes. If gas gangrene spores are suspected, fractional sterilization is used: boiling for 1 hour, exposure at room temperature for 12–24 hours (to allow spores to germinate into vegetative forms), and then re-boiling for another 1 hour.
Gas and chemical sterilization
Cold methods are necessary for heat-sensitive items such as optics (laparoscopes), fiber endoscopes, and heart-lung machines.
- Gas sterilization. Performed in hermetic devices using toxic ethylene oxide. The process is lengthy: 16 hours at 18. °C. When heated to 55 °C (and adding methylene bromide), the exposure time is reduced to 6 hours.
- Liquid (chemical). Method of complete immersion in containers with a lid. Preparations such as Cidex, 2.5% glutaraldehyde, hydrogen peroxide, or ethanol and chlorhexidine solutions are used. Cutting instruments (scalpels, scissors) are also chemically treated, for example, by immersing them for 30 minutes in 96% alcohol, as thermal exposure heavily dulls them.
Emergency method (flaming)
Permitted exclusively in hopeless situations. 15–20 ml of alcohol is poured into the bottom of a metal tray, the instrument is placed, and the liquid is ignited.
Important: The method is insufficiently reliable and extremely dangerous. An open flame in an operating room saturated with oxygen and anesthetic vapors can cause a fire and explosion.
Briefly: answers to topical questions
What chemical agents are used for liquid sterilization of surgical instruments?
For liquid sterilization of surgical instruments, the following are used:
- Chlorhexidine — alcohol solution.
- Pervomur.
What methods of quality and efficiency control of sterilization exist?
Methods for monitoring sterilization quality are divided into direct and indirect.
- Direct method — bacteriological culture from materials or the use of tests with a spore-bearing non-pathogenic culture.
- Physical control — verification of time, temperature control, and manometry.
- Chemical control — use of substances with a specific melting point (benzoic acid, resorcinol, antipyrine), historical reagents (sulfur powder, urea), and modern disposable thermal indicators.
- Mikulicz method — based on the decolorization of iodine-blued paper with starch paste.
What sequential stages does pre-sterilization cleaning (PSC) of medical devices consist of?
Pre-sterilization cleaning of medical devices includes the following sequential stages:
- Rinsing — washing instruments in running water with brushes for 5 minutes.
- Soaking — immersion in a special cleaning solution heated to 50 °C for 15–20 minutes.
- Washing in solution — processing with brushes or rammers in the same cleaning solution.
- Rinsing — washing with warm running water for 5 minutes, then with distilled water for 1 minute.
- Drying — drying in a dry-air sterilizer at 85 °C until completely dry.
- Additional cleaning — if necessary, using special ultrasonic devices to remove mechanical contaminants.
What is the fundamental difference between the sterilization process and disinfection?
The fundamental difference lies in the volume of destroyed microflora and the depth of impact.
| Characteristic | Disinfection | Sterilization |
|---|---|---|
| Goal | Destruction of pathogenic microorganisms only | Complete eradication of all forms of microflora |
| Microbe forms | Only active vegetative forms (spores survive) | Vegetative and spore forms |
| Depth of impact | Carried out only on the surface of the object | On the surface and in the depth of the object |
What types of surgical linen and dressing material packaging in drums (bixes) exist?
There are three main types of packaging for surgical linen and dressing materials in sterilization drums.
- Universal — contains material necessary for one minor typical operation.
- Targeted — includes a specialized set of linen and dressing material for a specific complex elective surgery.
- Specific — involves filling the drum with a strictly defined type of material or linen.
To remember autoclave modes: "Two by Twenty" (2 atm / 20 min for metal) and "One by Forty-Five" (1.1 atm / 45 min for rubber).
Class and exam questions
From what point does the time countdown begin during autoclaving?
The countdown begins strictly from the moment the specified operating pressure is reached according to the pressure gauge, rather than from the moment heating is turned on.
Why is it forbidden to use soda when boiling syringes?
Syringes, needles, and cutting instruments are sterilized only in pure distilled water. Sodium bicarbonate is not added due to the risk of surface damage.
When is it safe to open the door of a dry-heat sterilizer?
Instruments may be removed only after heating is completely turned off and the chamber cools down to a temperature of 70–50 °C.
What else to study on this topic
- Internal structure and operating principle of the autoclave (double-walled chamber)
- Preparation algorithm and packing methods for surgical linen in drum containers (bixes)
- Specifics of pre-sterilization processing of contaminated instruments
- Facility requirements and personnel clearance for working with pressure equipment
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Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.