Sterilizing equipment used in wound care

Why do we need to sterilize equipment for use in chronic wounds?

The treatment of chronic wounds is not a sterile process. There will always be bacteria colonies in a chronic wound, and our equipment needs to be clean and not necessarily sterile. However, we must avoid introducing new bacteria to the wound from our hands or via medical equipment. And we have to prevent the transmission of disease between patients. Diseases like HIV and hepatitis B can, for example, be transferred by contaminated equipment.

Another aspect you have to think about is how you will store your equipment once you have sterilized it. When we have to use the same equipment on different patients, we must sterilize the equipment between each use. This doesn't necessarily mean that we have to store the equipment in a sterile environment once it has been sterilized. Unless you are working at a bigger clinic where you have the resources to pack the instruments in single-use sterile bags once the sterilization process is done, your only option is to keep them "clean." We will discuss this at the end of this chapter. 

 

The tools we most often have to sterilize are forceps, scissors, and scalpels. Remember that it is essential to have scissors and clamps in the "open position" when sterilizing them, to ensure that the heat reaches everywhere.

The sterilization method you will use depends on your financial resources. Do you have access to a  regular electricity supply, and what volume of equipment that you have to sterilize.

Remember: if you have used equipment in a patient's wound (i.e., been in contact with wound exudate or other bodily fluids) and need to use it on another patient, you HAVE to sterilize it first! Simply wiping it down with alcohol is NOT  an option! This would be unethical as you cannot guarantee that you are not transmitting a potentially severe disease like hepatitis B, HIV, or bacterial infection. 

Can alcohol be used to "sterilize" equipment used for wound care?

No. A good soak in alcohol is not sufficient. Grooves in medical instruments trap protein-rich material. According to APIC (Association for Professionals in Infection Control and Epidemiology), ethyl alcohol and isopropyl alcohol are ineffective in sterilizing instruments because they lack sporicidal activity and cannot penetrate protein-rich materials. Isopropyl alcohol also lacks the ability to kill hydrophilic viruses. For these reasons, alcohol is only classified as an intermediate-level disinfectant. 

Can we use boiling water to sterilize medical equipment?

Yes and no. It is a method of disinfecting equipment, but it is not a true sterilization technique. Water boils at 100 degrees centigrade at sea level ( and at even lower temperatures at higher altitudes). This temperature is not high enough to destroy some types of pathogenic microbes, especially spores, even if you boil the equipment for a long time. 

Realistically this may be the only option at clinics with minimal resources. It is better than nothing. If you have to use the boiling water technique, you have to keep the equipment in boiling water for a minimum of 30 minutes. Most pathogenic bacteria and hepatitis B virus do not need that long boiling time, but the WHO recommends 20 minutes of boiling time at 100 degrees Celcius to inactivate  HIV. So with a 30 minute boiling time, your patients should be safe.

 

Be aware that stainless steel equipment will rust in a shorter time when you use this method regularly.  

Sterilization by dry heat

Dry-heat sterilization is one of the oldest sterilization methods from the time of the ancient Egyptians.

Dry heat requires more time or higher temperature to inactivate resistant microbes (e.g., spores) on products than steam. Dry-heat sterilization is as simple as baking in an oven, and you can indeed use a regular household oven to do this. Typical dry heat (160–180 °C) is the simplest, least expensive method, with fewer parameters and good penetration capabilities; however, it requires a long time. The equipment must tolerate high temperatures - equipment with rubber is not suitable for this sterilization method. 

There are two types of dry-heat sterilizers: the static-air type and the forced-air type. The static-air type is the oven-type sterilizer, as heating coils in the bottom of the unit cause the hot air to rise inside the chamber via gravity convection. This type of dry-heat sterilizer is much slower in heating, requires a longer time to reach sterilizing temperature, and is less uniform in temperature control throughout the chamber than is the forced-air type. The forced-air or mechanical convection sterilizer is equipped with a motor-driven blower that circulates heated air throughout the chamber at a high velocity, permitting a more rapid transfer of energy from the air to the instruments. Most modern household ovens today have a motor-driven blower, and they often do not cost more than about 500 US Dollars. For clinics on a limited budget, this may be the most convenient method of sterilizing equipment. 

The most common time-temperature relationships for sterilization with hot air sterilizers are 170°C (340°F) for 60 minutes, 160°C (320°F) for 120 minutes, or 150°C (300°F) for 150 minutes.

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Figure 1  There are many alternatives for ovens for dry-heat sterilization. There are small benchtop models  ( left) useful for low volume of equipment that needs to be sterilized. These can be purchased as cheaply as 50 US Dollars. There are bigger devices ( middle) with several trays and an air fan that distributes the heat evenly. If your clinic has a tight budget and needs a bigger oven, a regular household oven (right) will perform just as well.

Sterilization by steam autoclave

Fully automatic benchtop autoclaves requiring little maintenance are readily available today, also in Africa, but they are quite an expensive investment. The cheapest models cost from 2000 Us Dollars and upwards. From our own experience, the cheaper the model, the more prone it is to breakdowns, and it can be difficult to get hold of spare parts and replacement gaskets. If you invest in an autoclave, we advise you not to buy this online from Chinese marketing sites as you will have no one to contact if the autoclave needs servicing. Within two years of regular use, most of these autoclaves will need some service. We, therefore, advise you to buy these from a company based in your own country in Africa who at the same time can guarantee you that they can provide service for many years in case of breakdowns. The average lifespan of such an autoclave is 10-15 years, depending on how much it is used and if it is serviced regularly. 

An autoclave is, in principle, a fancy steam cooker - nothing more. Contrary to a regular steam cooker, however, the process can be more controlled- that is, you have various program settings with different temperatures/pressures, which may be helpful when you are sterilizing temperature-sensitive equipment. However, the tools we use in treating chronic wounds, namely scissors, forceps, and scalpels, tolerate high temperatures. If your only need is to sterilize equipment for wound care, then a proper autoclave may be an unnecessary luxury. 

In conclusion: If your clinic has the resources- by all means - go ahead and invest in an autoclave. If you do not have the resources, we advise you to invest in a special pressure cooker instead. 

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Figure 2  A benchtop steam autoclave is an excellent device for sterilizing medical equipment. Still, it is very costly, and you have to consider that it will undoubtedly need maintenance at some stage. If you only need to sterilize equipment to be used in chronic wound care, this may be an unnecessary luxury. If your clinic has the resources to acquire such a device and the supplier can guarantee follow-up and service, it is a time-saving tool. 

Sterilization of wound care equipment using a pressure cooker

Disclaimer: pressure cookers are potentially dangerous. The following text is a collection of information from the internet concerning the use of pressure cookers to sterilize equipment for the care of chronic wounds in areas where no other resource is available. Readers use this information at their own risk. Woundsafrica.com will not be held responsible for any accidents that can occur while using such a device.

In the absence of availability of a steam autoclave, sterilization using a pressure cooker is probably the most practical method for clinics with few resources. The standardized requirement for sterilization is a pressure of 15psi at a temperature of 121 C for 15 minutes. Most pressure cookers can achieve these pressures and temperatures.

In most manuals for pressure cookers, the following is stated: “Pressure cookers are not to be used for medical purposes, such as sterilizers, as pressure cookers are not designed to reach the temperatures necessary for complete sterilization.”  This is a standard judicial disclaimer all manufacturers automatically put in the manual. Pressure cookers will achieve the temperature and pressure necessary for sterilization as long as all the gaskets are working fine. Still, no company will want to guarantee that since pressure cookers are meant to make food cook faster and not sterilize medical equipment. So when you decide to use a regular pressure cooker for sterilization, you are using the product off-label at your own risk.

If you have some funds that can be used to purchase sterilization equipment, we advise you to buy a stainless steel pot sterilization autoclave. This can be purchased at aliexpress.com for as little as 120 USD  (minus shipment/import taxes). These are usually of heavy-duty quality and have better valves/gaskets, and a temperature gauge is built into the system. Again- if this is available in your own country - buy it locally even if it costs a little more there-  as long as the supplier can guarantee that you can acquire spare gaskets there when needed. 

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Figure 3  For small rural clinics, a specialized steam cooker autoclave is probably the most sensible investment for sterilizing medical equipment.  Some of these models run on electricity; others can be heated with, for example, a gas heating source.

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Figure 4 The SPECT Trust ( Sterile Processing Education Charitable Trust) has taught the safe operation and maintenance of portable pressure cooker autoclaves for several years. copyright spectrust.org

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Figure 5 If you would like to read more about the work of the SPEC Trust and the work they do, please click on the image above. copyright spectrust.org

If you have minimal funds, you must invest in a regular household pressure cooker. We advise you to buy the biggest available cooker you can get hold of. 10 L is relatively small, so we suggest going for å cooker which holds at least 20 L so that it is easy to place the instruments on a grate within.

It is important to understand that it is the steam that is effective- not the boiling water itself. The equipment has to be placed above the boiling water- so you have to buy or make some sort of grate on which you can place a tray with the instruments.

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Figure 6 If you are using a regular household pressure cooker, you will have to make some sort of grate so that the instruments can be placed above water level. We found this idea on instructables.com, where a simple grate is made from a stainless steel fruit basket. Click on the image above to get to the website. copyright: instructables.com

Read the instruction manual for the pressure cooker thoroughly. You are dealing with super-heated steam inside of a pressure vessel. 

You don’t need much water in the bottom of the pan when you are sterilizing equipment.   During the cooking process, steam escapes the pressure cooker, and you want enough water there to generate steam for the desired length of time. The minimum amount of water will always be stated in the instruction manual- usually, 3-4 cups of water are enough for a 20 min sterilization time.

Which heat source can I use for a pressure cooker?

Looking at available information on the internet, most producers advise not to use heat sources higher than 12000 BTU.

If you work at an off-grid clinic, you will likely not have a glass stovetop or an induction heat source. You may not even have electricity. In Africa, kerosene pressure cookers are widespread. The range of BTU for these cookers varies from 7000- to 14000. But the usual models available in Africa do not exceed 9000 BTU, which is appropriate for pressure cookers. To ensure that you don’t exceed the heat limit, we advise you to keep the flame at a max of ¾ of the maximal potential output.

Again: note our disclaimer, which states that woundsafrica.com does not take any responsibility for any accidents when using such devices.  

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Figure 7 A kerosene pressure stove not exceeding 12000 BTU in heat is considered a safe method of heating a pressure cooker.

Some pressure cookers explicitly state that they should not be used on a propane burner because the uneven and high heat source can warp the bottom of the cooker pan.  When looking at available literature on this, the warping effect happens when the heat exceeds 12000 BTU.   Some propane burners are considered safe when used at low flame.

Also- be aware that not all pressure cookers will work with ceramic glass stovetops  (with glass top stoves, we mean those that work with an infrared heating source - not the induction ones). 

Since many pressure cookers are made of aluminum, they will not work on an induction heat source.  There is, however, the possibility to get a “converter plate” which you slide between the induction burner and the aluminum pot.

Usually, your heat source is a gas stove ( considered safe) or a kerosene pressure stove ( use at low flame as mentioned earlier).

If you have to use fire as a heat source – place the pot about 15 cm above the flames.  The bottom of the cooker will get charred over time and will have to be kept clean.  Also- the flames may get around the pot to the handle and damage it. 

You will find examples of solar-thermal powered autoclave systems on the internet.  These are somewhat complex to construct without competent help- but once they are in place, they can provide a reliable source of heat for many years with little maintenance needs.

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Figure 8  Heating an autoclave with solar power is a realistic option and on the internet you will find many clever ways to construct one of these.  This particular example was published on 21stcentech.com and they state that this model needed about 90 minutes for the autoclave to reach a temperature of 121 celcius which is quite quick. This model was named Solarclave- it was built locally and the total costs were about 200 US dollars. Click on the image above to get to the website.  If you google " solar sterilization autoclave you will find many examples of well working models. 

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Figure 9 If you are interested in reading more about the efficacy of solar-powered autoclave systems, click on the image of the article from the American Journal of Tropical Medicine and Hygiene  and hygiene above

Are pressure cookers safe? 

Pressure cookers are generally considered safe – when used correctly. There have been accidents, yes. But considering that pressure cookers are in use in millions of homes every day, the risk of being run over by a car is higher.   A medical autoclave is, in principle, a fancy pressure cooker. Autoclaves also have chances of accidents when not used properly.

However, we cannot overstress this point – do read the manual of your pressure cooker thoroughly.   Buy the best brand you can afford. Also- make sure that you can buy replacement valves for the model you choose. If your supplier has these replacement parts available, buy them straight away- you never know when you can get hold of them again next time.

Do not let anyone use the pressure cooker who has not been trained thoroughly beforehand. Wear safety goggles when opening the pressure cooker.

There have been some models of pressure cookers that had faults. At the end of this article, you will find a list of pressure cookers recalled from the market for posing serious risks to consumers  (the list is not complete).

 

 

Before sterilization- how do I remove visible particles from my instruments?

We recommend using a toothbrush and warm water to get off any visible tissue fragments/blood from your equipment after use. If you are in the clinic, always have a container with water and dishwasher detergent to soak your instruments after use so that organic material does not stick to the instruments. If you are in the field/ home visits –you can carry a sealed plastic container ( available cheaply everywhere) prefilled with some water/detergent.

There exist a confusing variety of special cleansing agents for medical equipment. We will not go into any detail here. If you have the financial resources, check what local medical suppliers have available for this purpose. Special cleansing detergents made for cleaning medical equipment often have ingredients that more easily loosen blood and other tissue remnants from the tools. Some also include agents to prevent rust formation on your equipment. 

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Figure 10 It is wise to transfer your used equipment straight into a basin with lukewarm water and some detergent to avoid blood and other tissue residues from adhering too much.  Let them soak for about 30 minutes, then use a toothbrush to go over the parts like the hinges and anywhere where blood/tissue has been in contact. 

What do I do once the sterilization process in the pressure cooker is finished?

 

After boiling for 15 min in a pressure cooker, your equipment should be sterilized. We advise you to sterilize the equipment for 20-25 minutes to ensure that the desired pressure is held long enough. Once the cooker has cooled down and the lid can be opened ( read the instruction manual for your cooker!), we mustn't contaminate the equipment; otherwise, the whole process will be for nothing.

However, remember that we are talking about sterilizing equipment in chronic wound care. This is not a sterile procedure. We need clean instruments, but they do not necessarily need to be stored in a sterile environment after sterilization. We sterilized the equipment to eliminate the transmission of infectious diseases like HIV and hepatitis B  and bacterial infections between patients. If we sensibly handle the equipment without becoming hysterical after removing them from the autoclave, they will be clean enough to be used in wound care.

Never touch the instruments with bare fingers when you take them out of the autoclave, as you will contaminate them with the bacteria you have on your hands. The best method is to pick the instruments out of the autoclave with a sterilized instrument and transfer them into a clean container. Note- some plastic containers available at household stores withstand high temperatures - they can be sterilized so that you always have a number of clean containers available for storing your equipment. Make sure to let the instruments dry properly before sealing the container's lid; otherwise, rust will develop- even on stainless steel instruments. Make sure no flies can get to the instruments while they are drying!

Another method is to store your tools in cotton bags with a tobacco pouch knot. We advise not to make the bags too big – ideally, a size that accommodates max 2-3 instruments is ideal. Even better is a roll-up bag with pockets for each instrument- this is something your local tailor can easily make. Traditionally these bags were made of green material. Obviously, any color will do as long as the fabric dye is of ok quality. But the green does give it a professional touch! 

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Figure 11  Examples of cotton bags for sterilization.   The smaller bags with a tobacco-pouch closing system are ideal for å few instruments.  Some will prefer a roll-up bag with compartments for the individual instruments, as in the images above.  Place the instruments with the tip in the bottom of each pocket- in that way, you do not contaminate the tip so easily.

You can sterilize these bags in an autoclave, but it is unnecessary as long as the bags do not contact contaminated tissue. Do NOT put dirty equipment back into the bag- ever. If you are in the field, you have to have a separate container ( i.e., a plastic container for the dirty instruments!).

These cotton bags are not airtight, and therefore there is actually no use to sterilize them- but they should be clean. They should be washed at preferably 90 degrees Celcius between each use. Use common sense when removing instruments from the bags so that you don't contaminate the bag or other instruments with your fingers. Use, for example, clean gloves that have not touched anything else for removing the instruments. 

So - because some of you will be confused, let us explain this once more. We go through all the hassle of sterilizing the equipment, and then we place the instruments in a non-sterile bag? Yes- that is what we do in wound care- it is not brain surgery or open-heart surgery where everything needs to be super sterile. The purpose of sterilizing the tools is to prevent the transmission of disease between patients. After that, we need to keep the instruments as clean as possible, but they do not need to be stored sterile. 

By the way- single-use autoclavable pouches with clear see-through windows are convenient. You can place several instruments in these bags, which often are self-sealing, and set the entire bag into the autoclave. Once the sterilization process is finished, you can remove the bag without the danger of contaminating anything. We recommend you buy small pouches that hold about five instruments- after all, you will probably only need a scalpel, forceps, and scissors at each treatment session. If you purchase them from cheap sources like Alibaba.com, they are not that expensive.

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Figure 12 Single-use, self-sealing autoclave pouches are the easiest way to handle your instruments during the sterilization process. If you buy them in bulk from online stores, they only cost a few cents each, and they will undoubtedly simplify your workflow and ensure that your instruments are not contaminated. They tolerate regular steam sterilization in a standard autoclave or pressure cooker autoclave but make sure that the steam can get around all sides of the bag - i.e., you cannot place a pile of these pouches into the autoclave- there has to be some space between each pouch. Selv sealing pouches 90x 260mm or even 70 x 260mm are ideal for most instruments used in wound care. This image is taken from a manufacturer selling at aliexpress.com, where 200 bags sell for 14 USD – about 0,07 USD per bag.

Pressure cookers that have been recalled from the market

We want to make sure that you stay as safe as possible, and we have added a list of pressure cookers that have been recalled for posing serious risks to consumers. This list is not complete. If you google " recall list pressure cookers," you may get an updated list of recently recalled devices.

  • Alcan Pressure Cookers—recalled due to scalding injuries

  • Cuisinart Pressure Cookers

  • Welbilt Electronic Pressure Cookers—recalled after 37 burn reports; some consumers reported third-degree burns.

  • Mantra Pressure Cookers—recalled after contents of cookers spilled and burned two consumers.

  • HSN Bella Cucina Zip Cookers—recalled after eight incidences of consumer burn injuries were reported

  • HSN Ultrex-brand Pressure Cookers

  • Power Pressure Cooker XL

  • Maxi-Matic Pressure Cookers

  • Tristar Products—Power Pressure Cooker XL

  • Fagor America Cookers

  • Tabletops Unlimited Cookers

  • Maxi-Matic Cookers

  • Wolfgang Puck Worldwide Cookers

  • Double Insight Instant Pot Pressure Cooker

  • 3-Squares Tim3 Machin3 Cookers