LacerdaCare Journal Newsletter -Autoclaving and Use of Sterilization Pouches
April 17, 2024

LacerdaCare Journal Newsletter -Autoclaving and Use of Sterilization Pouches

Autoclaving and Use of Sterilization Pouches

LacerdaCare Journal Newsletter

Author: Micheal Cardozo, Regd. Pharmacist - Head of Pharmaceutical Operations & Strategy, LacerdaCare Pvt Ltd.


Autoclaving is an essential process in the medical field, used for sterilizing equipment that comes into contact with patients. This method is effective in preventing healthcare-associated infections (HAIs), which are a significant concern in medical settings. The use of sterilization pouches during autoclaving plays a critical role in maintaining the sterility of the instruments after the process is completed.

Principle of Autoclaving

The main principle behind autoclaving is wet heat sterilization. The high temperature and the steam is not sufficient to eliminate all microbes and their spores, in addition to that the sterilization process is carried out under pressure.[8]


The steam that is generated in the autoclave not only is effective as a medium to transfer the heat but it also helps coagulate the proteins and the microbial enzymes which disables the microorganisms' function.[8]


The pressure that is built in the chamber helps to attain a higher temperature easily. As we know that the relationship between temperature and pressure is directly proportional, so a higher pressure will yield a higher temperature. The pressure maintained during autoclaving is 1.1 bar.[8]


Time of sterilization is another major factor that ensures sterility. The longer the time of an autoclaving cycle the more effective is the  sterilization. Usually 15-20 minutes is sufficient to carry out sterilization but the time required depends on the efficacy of the device, depending on that the time required for complete sterilization is adjusted. To ensure that complete steam penetration and sterilization is complete, an indicator is used when can determine whether or not complete sterilization has taken place in the given time, and accordingly the time of sterilization is increased, usually 30-35 minutes ensures complete sterilization.[8]


Finally temperature is the most important factor which is responsible to eliminate the micro-organisms. The pressure and steam aid in the sterilization process but it is the temperature which eliminates the micro-organisms. Most of the microbes are killed at 100oC but this temperature is not sufficient to kill the spores. Hence a temperature of 121oC is required to ensure complete elimination of microbes and their spores.[8]


In short steam, pressure, temperature and time are used to eliminate any viable microorganisms and their spores.

Types of Autoclaves

Based on its use autoclaves can be classified as N class, S class and B class.

N Class Autoclaves:-

N class autoclaves are the most basic, they are not suitable for use in a medical setting since they lack a vacuum pump, steam is not able to penetrate too deep hence packaged articles, fabrics, hollow instruments, items within containers cannot be sterilized effectively. Only solid items can be sterilized in such autoclaves.[9]


S Class Autoclaves:-

These are intermediates between N Class and B class autoclaves. In S class autoclaves the steam is able to penetrate deep into the articles, due to presence of a vacuum pump which removes the air within the chamber before the start of sterilization so only steam is present within the chamber during sterilization. These autoclaves are suitable for sterilization of small to medium load.[9]


B Class Autoclaves:-

They are the most advanced type of autoclaves. They are able to sterilize any load, even the most complex. Since they have a fractionated pre-vacuum, they are able to remove almost all air within the chamber before autoclaving, and ensures that only steam is present in the chamber during sterilization. They also have a cooling cycle, which ensures that the chamber is cooled after sterilization. Class B autoclaves are mainly used in medical settings such as hospitals and dental clinics as they can sterilize any load.[9]

Sterilization Pouches

Sterilization pouches are specialized packaging used to contain instruments during steam sterilization. They often come with chemical indicators that change color to signify that sterilization has occurred. These pouches serve as a barrier to maintain the sterility of the instruments until they are used.

Usually the sterilization pouches come equipped with a chemical indicator. This indicator helps the user determine whether or not complete sterilization has taken place or not. Usually with time and use equipments like autoclaves, the efficacy of steam sterilization carried out by the autoclave may reduce due to various factors like leakages due to worn down rubber gaskets, wear and tear of the steam generator, fault in the vacuum pump etc., which may not effectively sterilize the equipment as intended and may lead to infections in the patients. Hence it is necessary to carry out periodic validation of equipments to determine whether or not they are working as intended. In the case of autoclaves an indicator helps in just that. Once the sterilization is complete there will be a color change on the indicator, if the color change has not taken place it means that proper sterilization is not carried out and the process and the equipment viz. autoclave has to be examined. Usually this is fixed by increasing the time of sterilization and fixing the faulty components. Please consult a qualified engineer to carry out the validation process and rectify any faults in the equipment.


Composition of Sterilization Pouches

sterilization pouch is typically made of medical-grade paper or Tyvek on one side, with a clear plastic film on the other side. The paper side allows the penetration of steam and facilitates the removal of air, while the clear plastic allows for easy identification of the contents and ensures that the chemical indicator is visible.

Using Sterilization Pouches

To use a sterilization pouch, the medical instrument is placed inside, and the pouch is sealed. During autoclaving, the plastic side should face the paper side of an adjacent pouch to ensure proper steam penetration. Post-sterilization, the pouches should be dry, and the chemical indicators checked to confirm that sterilization has been successful. It's crucial to use new pouches for each cycle as they are designed for single-use.