Disinfectants, Antiseptics and Sterilants

This page is intended to discuss products used in the preparation for a procedure. Instruction in the use of these products to process the theater can be found on the page titled Creating your Field.

One of the most important considerations when planning a procedure is how to maintain an appropriately clean surgical theater. The products we use to clean surfaces, our hands, and the operative site can help to prevent infection and influence whether a procedure is successful. We’ll begin by comparing different agents and methods used as disinfectants, antiseptics, and sterilants and then discuss their use. I’ve chosen to discuss some of the most common products but the list isn’t exhaustive. If you know of any products not in this list that you’d like me to assess and add, please let me know.

DISINFECTION: Preparation of the procedural environment

Disinfection is a process used to eliminate the majority of pathogenic microorganisms on inanimate objects. Ideally, the room in which a procedure occurs should consist entirely of non-absorbent durable surfaces which can be easily wiped down; however, for  implantation disinfection will mostly pertain to the surfaces upon which the procedure will take place and as a means of cleaning up following the procedure. Disinfection must always be preceded by cleaning. Gross contaminants like blood and soil can form little oasis of infectious material; disinfectants can’t effectively kill organisms in such a refuge. Cleaning consists of removal of any visible contamination using cleaning tools and detergents.

DetergentDetergent

Detergents generally consist of a surfactant and a water softener. The function of the surfactant is to bond to substances which aren’t water soluble and carry them away. An easy way to visualize this is to think about a greasy pan. Scrubbing the grease just causes it to smear. Dish soap is a surfactant which bonds to the grease and carries it away. Any hard surface cleaner can be used. I prefer a concentrated floor cleaning detergent.

 

 

 

 

Bleach0610170832b[1]

Chlorinated Lime such as used by Semmelweis is amongst the most widely known and easily obtained of disinfectants. It’s one of the many solutions that are called bleach. Chlorinated Lime Bleach is sold at concentration of 3-6% and it’s important to dilute prior to use for safety. A one part bleach to ten parts water is more than adequate but must be applied to surfaces that have already been cleaned to be effective as dirt, fats, and miscellaneous crumbs can serve as reservoirs of infectious material.

 

 

Disinfectant Concentration Contact time for most organisms Limitations
Bleach – Sodium hypochlorite 5% ( Diluted 1 to 10) 10 minutes Bleach is corrosive to mucous membranes, eyes, and other sensitive tissue. It’s reactive with many metals and can form a toxic gas if used with ammonia or on urine.

 

0610170845c[1]Alcohol

Another common disinfectant is alcohol. Either ethanol or isopropanol will work assuming a concentration of at least 70%. Because alcohol dries rapidly, it provides a particularly brief contact time. Additionally, it’s totally ineffective against many of the most feared blood-borne infections such as HIV and Hepatitis C. Very high concentrations with extended contact times have shown some promise, but overall alcohol is a poor choice as a surgical disinfectant.

 

 

Disinfectant Concentration Contact time for most organisms Limitations
Ethanol 95.00% 2-10 minutes Alcohols are not effective against spores, or biofilms. Precleaning or a surface is required for disinfection.
Isopropanol 70.00% 5-10 minutes

0610170832h[1]Quaternary Ammonium Compounds

The optimal disinfectant solutions to prepare rooms and surfaces for procedures are the quaternary ammonium compounds, most often referred to as quats. Quats generally have a very short contact time requirement killing the majority of pathogens in three to five minutes. Isolated, quats are only effective against most organisms. They are ineffective against a few particularly difficult to kill varieties such as tuberculosis. Formulations including both alcohol and quaternary compounds overcome this disadvantage yielding a combination that can kill just about any microorganism in less than two minutes. Quaternary and Alcohol solutions are the disinfectant of choice when preparing surfaces and cleaning up after a magnet implant.

Disinfectant Contact time for most organisms
Medline Super Sani-Cloth < 2 minutes

 

 

ANTISEPSIS: Hand washing and skin preparation

Antiseptics are antimicrobial substances meant to reduce the number of pathogens present. They differ from disinfectants in being intended to be applied directly to living skin. These agents are used not only to cleanse the skin which will be opened during a procedure but also to cleanse the hands performing the cut. Antiseptics tend to be less powerful than disinfectants but safer for contact with skin.

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Triclosan

Triclosan is a phenol agent found in soaps advertised as being antibacterial. Unfortunately, the list of pathogens resistant to triclosan is downright exhausting to read and it hasn’t been found particularly effective even against organisms without resistance at the strength it’s usually sold in. Studies have found that plain soap is just as effective. Triclosan simply isn’t a good option for antisepsis.

Antiseptic Concentration Advantages Disadvantages
Triclosan 0.1 to 1% N/A – ineffective at this concentration Triclosan of 2% or higher is effective against vulnerable bacteria, but is difficult to find in this strength and is outperformed by many other antispetics.

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Alcohol

The alcohols are also used as antiseptic agents. As an antiseptic, alcohol has the same drawbacks as when used as a disinfectant. It isn’t very effective against some of the agents of infection we most want to avoid. Alcohol based cleansers have their use between hand washings but should not be considered a replacement. Alcohol cleanser isn’t an appropriate antiseptic agent for hand or skin preparation for even a minor procedure.

Antiseptic Concentration Advantages Disadvantages
Isopropanol 40- 60% N/A – ineffective at this concentration Not effective at this strength
Isopropanol 70-90% Up to 99.99% of vulnerable types of bacteria are eliminated in under 30 seconds. Many types of virus and bacteria are not eliminated by alcohol and hand must be clear of oils and soiling.

povidone

Iodine

Iodine antiseptics are available in a number of different forms such as in solution with alcohol or as povidone-iodine. Any of these solutions are excellent as skin preparation agents. Iodine has the drawback of increasing scar tissue and healing time if applied directly to an open wound in high concentration. Iodine is also notorious for the bright red stain it provides. It is a great choice as an antiseptic although Chlorhexidine products have largely replaced Iodine due to a longer residual action and a wider range of vulnerable pathogens.

Antiseptic Concentration Contact time for most organisms Limitations
Povidone – iodine 9 – 12% 30 seconds to 2 minutes Iodine is an effective antiseptic but has been largely replaced by the more effective Chlorhexidine

 

0610170832e[1]Chlorhexidine Gluconate

The optimal antiseptic agent is Chlorhexidine Gluconate. Chlorhexidine is much gentler on tissue than disinfecting agents such as quats but remains active on the skin for as long as twelve hours at appropriate concentrations. This extended contact time provides a similar effectiveness to stronger agents provided adequate time is given. Isolated, Chlorhexidine is ineffective on certain pathogens such as poliovirus and thus is usually provided in combination with alcohol. Chlorhexidine Gluconate is available in different strengths. If being used as a handwash or skin preparation agent, 4% solution should be used and the site or hands should be scrubbed for a minimum of 3 minutes. Alternatively, a 2% Chlorhexidine with 70% alcohol combination is equally if not more effective. One of the major advantages of Chlorhexidine is its residual action.

Antiseptic Concentration Contact time for most organisms Limitations
Chlorhexidine Gluconate 2% with 70% alcohol 2 minutes Chlorhexidine is the preferred antiseptic for surgical procedures.

 

STERILIZATION: Preparation of Tools and Implants

Sterilization is any process which eliminates all forms of life or transmissible agents from a surface or instrument.

flaming_loop2Flame Sterilization

The earliest example is flame sterilization which was practiced by the surgeons of Rome but forgotten and lost by the time of the Middle Age barber surgeons. Flame sterilization was superseded in the eighteenth century by a device called an autoclave.

 

Flame sterilization is the oldest method of sterilization and still an effective one. Flaming isn’t used in a surgical environment because operating theaters are full of oxygen and flammable gases and flaming only sterilizes the portion of the instrument which is heated. This form of sterilization can only be used on metal instruments and red hot metal adds an undesirable potential source of injury to both the surgeon and the patient. Furthermore, impure fuel sources can leave carbon soot on the blade and the rapid heating and cooling affects the sharpness of the blade. Flame sterilization still has it’s place in the lab; it’s common in microbiology. But flame sterilization isn’t appropriate for even simple piercing much less more invasive procedures.

0610170857a[1]Heat Sterilization

Under normal atmospheric pressures, the boiling temperature of water is around 99.9 C. This is adequate to eliminate pathogens which will sicken a person if consumed, but not high enough to kill spores from organisms such as Clostridium perfringens. Were an instrument merely boiled, the spores of C. Perfringens could be left in a wound leading to conditions such as gas gangrene or necrotizing fasciitis. An autoclave functions as a pressure chamber. When pressurized, the boiling temperature of water rises to a point that all clinically relevant pathogens are killed.

Autoclaving is the sterilization method of choice for surgical instruments and non-disposable drapes, towels, and aprons. It’s not appropriate however for the actual magnet implant for a number of reasons. As discussed earlier, high temperatures adversely affect the magnetic capabilities of many magnets. An even greater concern however is the effect of temperature on the integrity of biocompatible coatings. Temperature variations such as created in an autoclave can cause metals to swell or shrink which cracks the coating and renders the magnet unsafe for implantation.

Laboratory autoclaves operate at temperatures as high as 134 C, which can kill nearly any pathogen in as little as 3 minutes. Portable autoclaves such as are used by dentists and occasionally by body modification artists operate at 121 C which requires fifteen to twenty minutes to achieve sterility. Items must be cleaned prior to sterilization and placed within a sterilization envelope with autoclave tape. This tape is an indicator that changes color when correct conditions have been met to achieve sterility. Only items specifically designed to be autoclavable should undergo the process. Many choose to simply purchase pre-sterilized disposable tools to avoid this process altogether. When later discussing instruments, disposable and sterilizable options will be considered where available. Autoclaving is an effective method of sterilization but it isn’t perfect. In 2004, a microbe called strain 21 was discovered which is able to survive temperatures above 130 C. As ominous as the name sounds, this finding is clinically irrelevant as strain 21 lives in a hydrothermal vent miles beneath the ocean surface and is incapable of reproducing at body temperature. Prions aren’t as innocuous. These infectious proteins which cause diseases such as bovine spongiform encephalitis and scrapies are able to survive for longer than twenty minutes of autoclaving at 134 C. Fortunately, acquired prion diseases are exceedingly rare and transmission from an instrument unheard of. Such risks remain theoretical but have driven the development and implementation of new chemical methods of sterilization.

Chemical Sterilization

EO SterilizerChemical sterilization uses a gas or liquid able to sterilize objects at low temperatures. Ethylene Oxide sterilization for example is a gas able to kill every known prion, fungi, virus, and bacteria even in spore form with one exception: Strain 21. The downside is that the gas is incredibly toxic, carcinogenic, and flammable enough to be used in thermobaric weapons. Other gas methods include Ozone, and Nitrogen Dioxide which have their own downsides. Overall, these are great methods of sterilization but not feasible in most settings.

Liquid immersion is the preferred method of sterilization for the magnet itself assuming gas sterilization isn’t available. Hydrogen Peroxide is a great sterilant at a high enough concentration. At 7.5% concentration, sterility is achieved by hydrogen peroxide in six hours. Products such as sporox are a good choice for soft metals, silicone or parylene. Hydrogen Peroxide shouldn’t be used on the M31 as it acts as a solvent for TiN. The same goes for bleach. A 1 to 5 dilution of bleach sterilizes in as little as 20 minutes but can dissolve the TiN right off the magnet.

OPA SterilantOPA is a very powerful sterilant. At a concentration of 0.575%, sterilization takes less than six hours but OPA has some serious downsides. It’s expensive and degrades in less than 28 days. It stains any tissue it contacts grey and has caused a few deaths due to anaphylaxis. While an option, OPA wouldn’t be my first choice.

 

 

 

One of the better choices of chemical sterilants for magnets is glutaraldehyde. It’s similar to formaldehyde in its use as both a fixative and preservative but differs in being metrex-procide-d-plus-10-3260non-carcinogenic. At a concentration of 2.65%, glutaraldehyde takes ten hours of immersion to sterilize a magnet. It will react with silicone and thus shouldn’t be used with a Haworth magnet. It’s important to irrigate the magnet well following immersion using sterile saline as glutaraldehyde shouldn’t come in contact with an open wound. Glutaraldehyde has a very short shelf life; it degrades in two weeks to a month. Also even being in a room with an open bottle for as little as fifteen minutes can irritate the lungs, throat, eyes, and nose. Contact can initiate a rash. There really aren’t any kind sterilization processes and overall, the very best option may be to buy everything presterilized. As of this time, there aren’t any easily purchased sterilants available that are safe to use without significant precautions and that are non-reactive with coatings such as silicone or titanium nitride.

Environmental Cleaning Tool Kit

It’s vital to have a set of cleaning tools which will only be used to clean the procedural area to avoid cross-contamination. This set should include:

Spray Bottles

Low Linting Cloths

Mop

Single Use Wipes

PPE

Non-Broom

Trash and Linen Bags