Water alone is not an effective cleaner! Its relatively high surface tension prevents it from being one. As long ago as 1965, it was suggested that agitation and water alone were insufficient for cleaning surgical instruments (Darmady EM, 1965). It was suggested that detergents were an“essential adjunct to the cleaning process”. If water alone is used as the cleaning medium then there is a considerable increase in the amount of mechanical energy required to produce a clean product.
水溶液本身并不是有效的清洗剂！它相对较高的表面张力会阻碍清洗的过程。1965年人们就已经查明，用水溶液来清洗外科手术器械是远远不够的（Darmady EM, 1965）。清洗剂是一个“清洗过程中的必需补充物”。如果仅仅只用水溶液来作为清洗剂使用的话，就需要借助大量机械的力量，才能将器械清洗干净。
This is highlighted perfectly in the ubiquitous“Sinner Circle” or TACT Pie (Fig.1). First devised by Dr Herbert Sinner of Henkel & Cie GMBH in 1959, it explains the relationship between the fourcomponents of any cleaning process: Temperature, Agitation (or mechanicalaction), Chemical action and Time. The original reference for this circle by Sinner is unavailable but it is recreated in Figure 1.
Sinner described each of the four components contributing to the overall effectiveness of the wash process (effectively the diameter of the circle). If one of the components was reducedthen one or more of the other components would need to be increased to provide the same level of performance.
This theory also helps explain the way in which different cleaning processes vary in their design. For example a manual wash process will have to compensate for the lower temperatures used that prevent scalding of the hands. Therefore reduced temperature will have tobe compensated for by an increase in time spent cleaning, more intense physicalaction or better chemicals. Conversely an ultrasonic process could have agreater mechanical action or agitation which could shorten the time. However it is the chemical action component that often allows for the largest improvements in wash processes and the circle illustrates perfectly that removing detergent completely (or even using a poor detergent) would need large increases in the other components to get a comparatively clean instrument.
Taking Sinner’s circle, any product whether acting alone or in combination with others that allows the substitutionof chemical energy for some of the mechanical energy required for removing soiling could be classified as a detergent. But there are certain prerequisites of the process that dictate the formulations we need.
completely soluble in water;
non-corrosive to, and compatible with medical devices;
a good wetting agent with penetrating ability (wetting is the ability to spread over a surface);
effective against the forms of soiling present on used medical devices such as proteins, carbohydrates and fats;
capable of dispersing or suspending soil (emulsification);
easy to rinse off and leave no harmful residues;
kind to the environment.
There are almost as many formulations of detergents as there are instrument types. It is therefore vital that the correct detergent is selected. Formulations suitable for manual wash processes are not necessarily suitable for automated ones. The amount of pressure generated by the spray arms of awasher-disinfector might cause excessive foam when used with a detergent designed for manual wash. An automated process detergent may not be suitable for immersing hands in and could cause skin problems.
The formulation of detergents can be divided according to their pH value or whether they contain enzymes to assist with the chemical action. The common pH types are acidic (pH typically less than 5), neutral (with a pH of between 6 – 8) and alkaline (usually greater than 8). Some formulations are so called high-alkaline with pH values10 – 14. Medical device manufacturers reprocessing instructions will often specifyany limitations regarding the pH of acceptable detergents and it is becoming more common for neutral detergents to be specified. Some materials such as aluminiummay be damaged by very high pH alkaline detergents (or more specifically a high pH wash liquor once the detergent has been dosed). Acidic formulations are goodfor removing inorganic material such as Calcium Carbonate deposits and Iron Oxide. Alkaline formulations are particularly good at removing organic material.
Many modern detergents now contain enzymes. Typically these are neutral pH detergents. Enzymes are large protein molecules and like other proteins they are made up of long chains of amino acids. They speed up a chemical reaction but are not changed in the process. As enzymes are catalysts, they can be used to speed up chemical processes or to make reactions take place that otherwise would not. Enzymes bind to the startingmaterial (substrate) catalysing the reactions then releasing themselves from the products so that they can react again. However for a molecule to be broken down, aparticular enzyme type must be used targeted to that molecule type. Further articles in this series will discuss enzyme types in more detail. Enzymes are heatsensitive and therefore must be used in the correct temperature range specified by the detergent manufacturer.
Other important components of adetergent are surfactants, sequestrants and corrosion inhibitors. Surfactants are Surface Active Agents and change the properties of the wash solution by lowering the surface tension of the water. Foaming agents, emulsifiers, and dispersants are all types of surfactant which suspend gases, immiscible liquids (liquids that don’t mix such as oils and water), or a solid in water. This provides increased penetration and better soil removal by suspending and keeping there moved contaminants in the wash solution.
Sequestrants are included indetergents as water softening agents. Hard water mineral ions can interfere with the action of surfactants and sequestrants are often incorporated to offset hard water effects. However softening water before it enters the wash process is a far better solution to the problem.
The prospective purchaser ofdetergents needs to ask themselves some fundamental questions before buying:
Is it for manual or automated machine use?
What instruments/devices do I intend to clean?
What soiling will I encounter?
What do the instructions for use say? Do they specify a pH?
Do you require a specific surgical instrument or endoscope detergent or does it need to work with either?
If it is for Manual Use: Will it work at hand-safe/comfortable temperatures?
If it is for Manual Use:
Will it work at hand-safe/comfortable temperatures?
Is it sold as a manual wash detergent (e.g. correct foaming level, safe pH)？
Is the contact time compatible with your process/expectations?
If it contains enzymes:
Is your was hing temperaturecompatible with the enzymes used?
Are you aware of any requiredcontact time for the enzymes to work?
For Machine Use: Will it work with my washer-disinfector wash stage temperatures? Is it sold as a machine wash detergent (e.g. correct foaming level)? Is the contact time compatible with the wash stage time? Is the chemical compatible with the machine construction? Is the chemical compatible with any subsequent chemicals used in the machine such as disinfectants? Does it pass a chemical process residue test within your machine type? Has it been type tested as being compatible with your machine?
For Machine Use:
Will it work with my washer-disinfector wash stage temperatures?
Is it sold as a machine wash detergent (e.g. correct foaming level)?
Is the contact time compatible with the wash stage time?
Is the chemical compatible with the machine construction?
Is the chemical compatible with any subsequent chemicals used in the machine such as disinfectants?
Does it pass a chemical process residue test within your machine type?
Has it been type tested as being compatible with your machine?