Disinfection in anaesthesia resuscitation

2021-05-16 12:40 AM

Usually, sterility is assessed by the user and is generally understood to be completely free of bacteria, once the media has been disinfected.


In the mid-nineteenth century, although the world had carried out complicated surgeries, the mortality rate in surgery was still high, many types of surgery such as open fracture, mastectomy, goitre surgery had high mortality rate. up to 50%. It was not until Pasteur discovered bacteria that it was known that bacteria were a cause of high mortality in surgery.

In 1890, the 17th International Congress of Surgery in Berlin defined the principle of aseptic surgery. In 1893 Mikulicz used rubber gloves for the first time in surgery, which greatly reduced the mortality rate.

The microorganisms that cause disease are not normally present in the body's organization, they only present and cause disease when they enter the body. Therefore, every surgical procedure, from small tasks such as changing wound dressings to complex surgeries, requires aseptic. In order to achieve sterility, all materials, tools and equipment must be disinfected before use.

Aseptic: A way to protect disinfected instruments as well as clean incisions from infection. Sterility is achieved only after physical and chemical sterilization methods have been applied.

Disinfection: The use of physical or chemical methods to kill any microorganisms in a range of environments, as well as materials and instruments used in surgery, in the operating room which itself cannot be sterile.

Usually, sterility is assessed by the user and is generally understood to be completely free of bacteria, once the media has been disinfected. That concept is not entirely correct. It must be understood that the process of disinfecting microorganisms is killed according to mathematical laws. When disinfected, a percentage of the microbial population is killed in a unit of time. This means that there is a percentage of the bacteria that will die and a percentage that will remain alive for a certain time after the initial contact with the disinfected vehicle.

Today, to evaluate a material, an instrument is considered sterile, based on the MSI (Microbiological Safety survival Index) value. MSI was developed in Canada to measure the quality of products considered sterile after sterilization. Based on the accepted MSI value of one million sterilized products, there is a 99.9999% chance of being sterile. The higher the MSI value, the more sterility is guaranteed. Thus, absolute sterility cannot be achieved because the sterilization process cannot completely kill the bacteria and there is still a very small percentage of survival, but the number of bacteria is not enough to cause an infection.

Disinfection methods

The bacteria with the most resistant spores are because it is able to withstand agents that destroy it from the outside. Therefore, the choice of a sterilization method to achieve sterility depends mainly on the nature of the item to be disinfected. The time required to kill bacterial spores, each medium, is standardized. Like each sterilization method has its advantages and disadvantages.

Disinfection methods include 2 main methods as follows:

Disinfection by physical methods.

Chemical sterilization.

Physical methods

Disinfection by heat (moist heat)


Moist heat in the form of heat saturated under pressure is a physical agent for the destruction of all microbial life forms including spores. Heat produces heat that destroys microorganisms, but this process is due to the addition of moisture because heat alone is not enough to kill bacteria. Heat and moist heat are obtained by increasing the temperature of the water. People create a pressure greater than atmospheric pressure to increase the temperature of the water to create high heat to destroy the vitality of microorganisms, and the heat combined with moisture will deform the substance. proteins inside the cell.

The heat is saturated when the steam containing a maximum amount of water evaporates. Direct exposure to saturated heat is the essence of humid heat sterilization. When the hot steam enters the chamber for sterilization under pressure, it condenses on contact with the material to be autoclaved. This condensate releases heat, both generating heat and wetting so it provides heat and moisture.

Disinfection by this method is referred to in terms of degrees of heat and contact time without mentioning the weight of pressure because pressure increases the boiling point of water but it has no effect on killing microorganism. With this method most normal microorganisms are killed in a few minutes at 54-55 0 C, some microorganisms with spores will endure the temperature at 115 0 C for more than 3 hours. However, no bacteria can survive at 121 0 C for 15 minutes of exposure. Therefore, if the temperature is increased, the contact time will be reduced.

A relationship between temperature and minimum contact time must be maintained throughout the sterilization process to complete an effective disinfection measure. The contact time and temperature reached inside the materials and tools to be disinfected depends on the size and type of materials and tools contained in the box (bin) to be autoclaved.

How to operate:

Put tools and materials to be steamed into the autoclave, taking care not to compress them tightly because it will hinder the passage of steam. Close the lid tightly and heat, this time the valve is not closed, when the hot water boils to push the air out, close the valve in the pot, leaving only steam.

When the pressure gauge reads 3 atmospheres, keep that pressure for 45 minutes to 1 hour. When the time is up, cut off the power source, wait until the pressure gauge reads zero, open the valve to let the steam out and the steamers will dry. Alternatively, the tool can be dried with a vacuum dryer (purified air).

It takes about 15-20 minutes to dry the tool.

The equivalent pressure values ​​​​when autoclaving by this method are 1 atmosphere equivalent to 120 0 C. 2 atmosphere equivalent to 134 0 C. 3 atmosphere equivalent to 143 0 C. To assess the temperature achieved inside the autoclave, people apply the following measures:

Test temperature by melting of some substances: Sulphur melts at 120 0 C. Antipyrine melts at 114 0 C. Salicylic acid melts at 157 0 C.

- Temperature test by discolouration: Lead carbonate mixture 1g, Lithium sulphide 0.5g becomes black at 100 0 C. Lead carbonate mixture 1g, Lithium Carbonate 0.3g, 0.1g sulphur becomes gray at 100 0 C/30 minutes, 110 0 C/3-4 minutes and 120 0 C/30 seconds.

Use the coloured indicator tapes on the autoclave box.

In addition, test tubes containing highly heat-resistant bacteria such as subtilis or spore bands are used. The tubes containing these microorganisms are placed in the autoclave, after autoclaving, cultured immediately to see if the bacteria are dead or not. This is the most accurate method, but it is complicated and takes a long time, so it is only applied to periodically check the sterilization efficiency of the autoclave.

The advantages and disadvantages of this method are:

Advantages: This is an easy, safe method that does little damage to the autoclave. Fast steaming process, short cycle time. Economically cheap and easy to equip.

Disadvantage: Must pack the steamer carefully, steaming a lot can easily create overload causing the temperature not to reach the standard temperature, easy to wet the steaming material if it is not operated properly. The steamer must be cleaned if there is oil or fat that reduces heat absorption. The heat that is in direct contact with the steamer repeatedly will damage it quickly.

Heat sterilization (drying)

The power source is coal or electricity, the temperature in the drying chamber will gradually increase to reach 1800C. The steaming time is 15-45 minutes. At this temperature, organic molecules are decomposed into carbon, so sterility is absolute. But the downside is that tools are quickly damaged, plastic, rubber, and fabric will be burned, so they cannot be applied.

Sterilization by boiling method

Heat-resistant fungi, bacteria and especially viruses and bacterial spores can live in boiling water of 100 0 C for several hours. Therefore, sterilization by boiling alone should not be at atmospheric pressure. However, in difficult circumstances, it is possible to disinfect tools by boiling at a temperature of 100 0 C / 30 minutes, if every 1 litter of water adds 10 grams of sodium chloride, sodium bicarbonate or sodium borate, the temperature can also be raised. reached 105 ° C.

Disinfection with ultraviolet light

The beam emitted from a mercury lamp has a long wavelength that readily absorbs organics even with transparent instruments. The bactericidal effect when near rays and clean instruments. Therefore, it only applies to a small area. The disadvantage of this method is that it is not effective when the room is polluted and the objects with contrast do not absorb ultraviolet rays.

Disinfect by ultrasonic

Ultrasound acts with high frequency on fluids and nearby air. In the liquid environment, ultrasound creates free chemical radicals, H+, which is a radical with a strong redox effect, OH-, a radical with a strong oxidizing effect and it can polymerize to form hydrogen peroxide. Therefore, on a liquid medium, ultrasound has both strong oxidizing and reducing effects, which is the antiseptic effect. Currently, people use ultrasound with a frequency of 50,000Hz to clean metal tools before disinfecting by other means.

Disinfection with radiation

Use radiation (X-rays or radioisotope emitting rays to disinfect). The main effect is due to radioactive rays separating electrons, turning objects into negative and positive ions. Applying this method shows that each type of bacteria is sensitive to each ray differently. The effect is different on each medium. Sensitivity to the rays also varies according to the type of bacteria, fungus or virus.

Disinfection by chemical method

Standard of disinfectant chemicals

An ideal chemical disinfectant must meet the following criteria: Has a bactericidal effect for a long time and does not damage live tissues. Easy to use and easy to clean after disinfecting. Ensure or do not damage the tool. In fact, there is no perfect chemical that fully meets the above criteria. Therefore, appropriate chemicals are used for each purpose.

Factors affecting the effectiveness of a chemical used to disinfect

Time factor: Each substance requires a different duration of action. For example, javel water works faster than hexylresorcinol.

pH factor: Has an influence on the strong or weak effect of that chemical.

Temperature factor: The antiseptic effect increases if the temperature increases. However, only to a limited extent and if the temperature is too high, it will hurt the organization.

Environmental factors: The dirty environment of the drug will reduce the effect.

The concentration of drug, solution: High concentration of the strong drug, this is also an important factor. According to Bean, the drug will reduce the effect more than 1000 times when the concentration is reduced by half.

Chemicals used to disinfect

 ethylene oxide  gas(EO)

EO has the ability to kill all types of microorganisms including spores when in direct contact for a certain period of time. The main mechanism is inhibition of normal protein metabolism and protein regeneration. To have a bactericidal effect, the material to be disinfected must be in direct contact with EO gas. In practice, because EO gas alone will cause fire and explosion, one must neutralize it with another gas such as hydrogen Carbone or CO2. Disinfection with this gas depends on the concentration, temperature, humidity and time of exposure to the gas. The gas contained in a mixed metal vessel consists of 10-12% EO. The concentration of EO for disinfection is: Every litter in the sterilization chamber contains about 450-800mg of EO gas.

The factors affecting the bactericidal ability of EO gas are temperature and contact time. As the temperature increases, the contact time can be reduced. However, if the material to be disinfected is made of plastique or rubber, it can only withstand a maximum temperature of 600C, so EO gas is used at normal ambient temperature and for a longer exposure time. effective against spore-forming bacteria. The average sterilization time EO is 3-6 hours.

The advantages and disadvantages

Advantages: As a sterilization method to replace the sterilization method by temperature for some materials and tools that cannot be applied by this method. Maintain a longer sterilization time.

Disadvantage: The sterilization time is longer than the temperature method. Expensive gas, special equipment. The most toxic are some materials that easily absorb EO gas such as rubber, silium. EO can cause burns.

Disinfection with active ingredient glutaraldehyde

In addition to EO gas, glutaraldehyde can be used to disinfect and disinfect materials that are sensitive to temperature. The method of application is similar to sterilization with EO gas. However, direct contact time requires ≥ 6 hours.

Advantages: The solution of the active ingredient glutaraldehyde has low surface tension, so it is easy to penetrate, easily penetrate and increase the concentration inside the disinfected material. Safe, non-irritating. Do not damage the tool. Rubber and plastic are not absorbed. Glutaraldehyde has a bactericidal effect at normal temperatures.

Disadvantage: Solution must be activated by mixing with buffer solutions. If using alkaline solution, glutaraldehyde easily changes with pH and will lose its effect after one day of activation. It has a special smell and is toxic, so it also affects the user.

Disinfect with alcohols

Ethylic alcohol: After a few seconds of contact, it kills bacteria without spores, inhibiting the activity of viruses.

Propylic alcohol: Strong bactericidal but the downside is strong irritation.

Disinfect with formol

Formol is a strong disinfectant but quite toxic. In practice, it is used in two forms: a 4% formaldehyde solution and a polymerized form of trioxymethylene. Formol 4% is often used to disinfect operating rooms, in addition to being used to disinfect ventilators.

Trioxymethylene is often used to disinfect non-autoclavable instruments such as some surgical machines, plastic items, endotracheal tubes, etc.

Other Disinfectants

Hypochlorite: As sodium salts with different concentrations, hypochlorite is presented in many different forms such as javelin solution, Dakin.

Iodine alcohol solutions: 5% solution is a strong antiseptic but is irritating to the skin.

Hydrogen peroxide 3%: Has antiseptic effect, cleans dirty wounds.

Peracetic acid 2% solution.

Trivalent ammoniums, phenols and derivatives.

Heavy metals such as mercury.

Surgical site infection and preventive measures

Surgical site infection


An incision is considered infected when pus is detected from the incision. This definition does not address the question of whether or not microorganisms are isolated from the wound, although this is a determining factor in treatment. In clinical practice, 25-50% of wounds are infected but bacteria cannot be isolated, whereas bacteria can still be detected from well-healed wounds. Therefore, the diagnosis of an infected wound should be based on clinical symptoms and especially the presence of pus in the wound.

Classification of incisions

Based on the characteristics of the incision, people are divided into 4 types as follows:

Clean operation: Surgery on clean organs under aseptic conditions (except for respiratory, gastrointestinal, urinary and genitourinary tract interventions). The wound is clean, neatly sutured, the skin is closed, and there is no drainage.

Clean-contaminated operation: Clean-contaminated operations are areas of surgery that are clean but interfere with organs with parasitic bacteria but have not yet caused disease or drained wounds.

Contaminated operation: Incisions and wounds that are initially clean but during surgery come into contact with hollow organs with parasitic bacteria or cause a lot of fluid to flow out from these organs or major errors in aseptic technique during surgery.

Dirty operation: These are old wounds and injuries with signs of infection at the surgical site or incision right before surgery.

The danger elements

Surgical agency

Bone surgery often infected with staphylococcus aureus, green pus bacilli. Lung surgery with pneumococci, tuberculosis bacilli. Gastrointestinal and urinary surgery with intestinal bacilli.

Patient anatomy

Elderly patient. Fat. Preoperative infection is present, even at sites far from the surgical site. Are taking corticosteroids or immunosuppressive drugs. Diabetes. Malnutrition.

Spot elements

The incisions are crushed, tissue damage, bleeding profusely during surgery. The incision has a foreign body. Poor local blood supply. The incision is located near the groin and anus. Long incision, with hematoma, fluid or virtual cavity under the skin. Incision with drainage

Nature of surgery

Emergency surgery. Dirty surgery or contaminated surgery. Major surgery, long surgery time.

Prevention of surgical site infection

Requirements for the operating area

The operating area must be built far from infected places such as infectious departments, morgues, toilets...

There are separate sterile and sterile operating rooms.

There is a system of doors and one-way passages.

There is a filtration and air conditioning system, ensuring the temperature in the operating room is 24-28 0 C and the humidity is 50%.

Walls and floors must be smooth and waterproof.

Ensure daily cleaning and disinfecting regulations.

There are showers and changing rooms for operating room staff.

Instruments in the operating room are kept to a minimum and neatly arranged, easy to clean.

Limit the number of people entering the operating room, have a system of glass doors or television to serve people who need to see the surgery.

Requirements for operating room staff

Before entering the operating room, they must change clothes, wear a hat, wear a mask and wear their own boots or slippers according to the regulations of the operating area.

Do not walk or talk much in the operating room.

People with infectious diseases are not allowed to enter the operating room.

Those entering the morgue are not allowed to enter the operating room for 24 hours.

It is not allowed to bring stretchers or vehicles to transport patients from the operating area to the outside and vice versa.

Operating room staff who have changed into sterile clothes are not allowed to go out of the operating area, if necessary, they must change back in and out.

Surgeons and staff must wash their hands, wear clothes, and wear gloves properly. During surgery, they must strictly follow the rules of aseptic, consciously and correctly perform clean and dirty operations.

Requirements for the patient

Prepare the patient before surgery:

For elective surgery cases:

Stabilize all existing infections.

Provide nutrition to improve physical condition if there is malnutrition.

Good control of blood sugar in patients with diabetes.

Wash with antibacterial soap the night before surgery.

Shave only if excessive hair affects the incision.

For emergency surgery cases due to insufficient time allowed but also need to prepare as best as possible. The surgical area should be kept clean, especially open wounds should be washed with soap and water.

Skin disinfection

The ideal antiseptic is one that kills both the skin and the pores, must be able to disinfect all types of bacteria. In addition, the drug does not irritate the skin, does not cause allergies and is not destroyed by alcohol, soaps and other organic substances. In fact, there are currently no antiseptic compounds that meet all of the above requirements.

Some antiseptics have been used in clinical practice:

Ethanol: Has the effect of killing bacteria, fungi and can kill viruses. The drug acts quickly if in high concentrations.

Iodine alcohol: Has the effect of killing bacteria, fungi and viruses. The drug can be irritating to the skin and may be less effective if there is a lot of blood or serum in the wound.

Gentian violet: Has only a bacteriostatic effect and can slow wound healing.

Red eosin: Has bacteriostatic and fungal effects and does not slow wound healing.

Disinfection method:

For dirty wounds, before disinfecting, clean the surgical area with soap and water.

Use an antiseptic solution to disinfect the incision, starting from the centre and then gradually moving outward in a spiral.

The antiseptic area must be large enough so that during surgery the surgeon's hand does not come into contact with the unsterilized skin. The antiseptic solution should be left wet on the skin for at least 2 minutes.


The patient must be covered with a sterile dressing, leaving only the surgical site and areas required for the operation of the anesthesiologist. The surgical incision must be spread so as to ensure a spacious surgical field, convenient for surgical operations, but also to minimize pollution. The instrument table must be covered with a sterile plastic sheet on the bottom and a sterile towel on top.

Wound dressings

After surgery, the incision must be cleaned, disinfected and covered with a sterile bandage. When changing the surgical wound dressing, it is also necessary to follow the aseptic procedure.