Sterilization is a term referring to any process that kills all forms of life on or in a material. Heat, chemicals, and irradiation are commonly used for sterilization. Any instruments to be sterilized will need to have surface debris removed to allow the sterilizing environment to reach the surface of the equipment. Expeditious sterilization or disinfection may be achieved in primitive settings using chlorine bleach, boiling water, pressurized steam, dry heat or open flame.
Chlorine Bleach in Sterilization
Chlorine bleach can be used as a sterilizing agent or at least a disinfectant (reduces the number of infectious organisms). Household bleach consists of 5.25% sodium hypochlorite. It is usually diluted to 1/10 immediately before use, because it decomposes over time. This solution will kill many bacteria instantly, but for even greater bacterial killing, your instruments will need to be exposed to this solution for 20 minutes (and are then nearly sterilized). A more concentrated solution may be needed to kill tuberculosis (1/5). Bleach is highly corrosive and may damage some sensitive instruments.
Is Boiling Something Enough to Sterilize It?
Boiling instruments in water for 15 minutes will kill most infectious organisms, but does not achieve true sterilization. Using boiling water for processing instruments is simple, low-tech, and generally readily available, however, and if it’s all you have, it’s better than nothing.
How an Autoclave Works
A medical autoclave can be used to reach true sterility on the surface of instruments placed within it. This instrument produces steam under pressure which allows the inside temperatures to reach 121-134°C (250-273°F). If instruments are held in an autoclave at 121°C for 15 minutes or three minutes or 134°C then sterilization can be achieved. Be aware that instruments wrapped in layers of paper or cloth will require longer treatment times to allow the steam to pass through the wrapping to the instruments. Special tape is applied to wrappings on instruments. This tape is temperature sensitive and will change color if the proper sterilizing temperature has been reached within the autoclave. The tape itself does not prove sterilization was successful because it doesn’t indicate the length of time the temperature was elevated. Bacterial cultures are often placed in an autoclave daily or with each run of sterilizations. The cultures are then checked to make sure the bacteria was killed- further verifying successful sterilization.
Using a Pressure Cooker as an Autoclave
Pressure cooking is similar to autoclaving and, if performed correctly, could render contained material sterile. To reach a sterilizing temperature the 15 psi setting should be used. Consult your pressure cooker owners manual to identify the temperatures achieved in your particular model. The objects to be sterilized should be exposed to steam heated to 121-134°C for at least 30 minutes. Be aware that pressure cooking is not legally or medically considered an appropriate technique for sterilizing medical instruments.
Dry heat can be used to sterilize items as well, but this technique takes a longer time than steam because the heat takes longer to be transferred to the surface of the instruments. Sterilization with dry heat requires at least two hours at 160°C (320°F). This can also be achieved more rapidly using higher temperatures such as 190°C for six minutes for instruments or twice that time if the objects are wrapped.
An open flame may be used to heat equipment/instruments and achieve sterilization. Unfortunately this may damage sensitive materials including the tempering of metals. This also requires a cool down period before use.
Sterilization may be one of the most critical parts of surviving some kind of disaster or other disruption event. It’s important to understand the methods available to you in a primitive situation, and prepare to have what you need on hand.
F250Doc is a board certified surgeon who seeks to help people prepare for various situations.