In a health facility, there are a wide range of chemicals and disinfectants used for various clinical, nursing, laboratory and radiological procedures.
The following cleaning and disinfecting materials are commonly used in healthcare settings:
Soaps are generally alkaline compounds used to remove dirt and organic matter from surfaces. They act mainly by loosening the dirt and organic matter from the surface. Hence, the mechanical action of scrubbing/brushing followed by a water rinse is important when using soap for cleaning any surface. Soap has little or no antimicrobial activity. Soap solutions can allow growth of bacteria when used for environmental cleaning, they should be prepared just before use; used immediately and the leftover discarded. Soap can be used to clean large environmental surfaces to remove dirt, organic matter, grime, oils, and residues of disinfectants. It is cheap, easily available and along with proper mechanical scrubbing/brushing can remove almost 80-90% of microbes on a surface. The surfaces should be adequately rinsed to remove all soap residues. This increases the effectiveness of subsequently used disinfectants.
In healthcare settings, “Alcohol” generally refers to two water-soluble chemical compounds – ethyl alcohol and isopropyl alcohol. Alcohols are rapidly bactericidal rather than bacteriostatic against vegetative forms of bacteria; they also are tuberculocidal, fungicidal, and virucidal but do not destroy bacterial spores. Optimum bactericidal concentration is 60%–90% solutions in water (volume/volume). The most feasible explanation for the antimicrobial action of alcohol is denaturation of proteins.
Alcohols can be used for disinfecting small surface items such as thermometers, stethoscopes, equipment buttons, rubber stoppers of medication vials etc. The main use of alcohol in healthcare settings is as an antiseptic and for disinfection of small items/surfaces.
Alcohols are not recommended for sterilising medical and surgical materials principally because they lack sporicidal action and they cannot penetrate protein-rich materials. They should not be used to clean/disinfect large surfaces as they evaporate quickly leading to unreliable disinfection. They can also denature and fix proteins to the surface. Alcohols are highly flammable – they should be stored in a cool ventilated area and should not be used near open flame. They damage the shellac mountings of lensed instruments, tend to swell and harden rubber and certain plastic tubing after prolonged and repeated use, bleach rubber and plastic tiles and damage tonometer tips.
An iodophor is a combination of iodine and a solubilising agent or carrier; the resulting complex provides a sustained-release reservoir of iodine and releases small amounts of free iodine in aqueous solution. The free iodine is responsible for the antimicrobial action. The best-known and most widely used iodophor is povidone-iodine.
Iodophors are bactericidal, mycobactericidal, and virucidal but require prolonged contact times to kill certain fungi and bacterial spores (weak sporicidal activity). In a hospital, they are often used for ‘’Part Preparation’’ prior to surgery or any invasive procedure.
Antiseptic preparations of iodophors should not be used as environmental or equipment disinfectants because of concentration differences and surface staining.
Quaternary Amonium Compounds (QUATs/QACs)
Chemically, the quaternaries are organically substituted ammonium compounds. Examples of the chemical names of quaternary ammonium compounds are Benzalkonium Chloride, Benzethonium Chlorite, Cetrimide etc.
The quaternaries can be used in ordinary environmental sanitation of noncritical surfaces (e.g., floors, furniture, and walls), and for disinfecting medical equipment that contacts intact skin (e.g., blood pressure cuffs).
Although QUATs are widely used as disinfectants, they should not be used to disinfect patient care items such as catheters, cystoscopes etc. as infections have been reported from such use. The quaternaries are good cleaning agents, but high water hardness and materials such as cotton and gauze pads can make them less microbicidal because of insoluble precipitates or cotton and gauze pads absorb the active ingredients, respectively.
As with several other disinfectants (e.g., phenolics, iodophors) gram-negative bacteria can survive or grow in them. Therefore, cleanliness in preparation and immediate use are important practices to be followed in their use. Prepared solutions should not be stored for extended periods of time.
Chlorine and Chlorine Compounds
Chlorine products are available as liquids or solid powders. The strength of a chlorine solution is expressed in ppm of free chlorine. They have a broad spectrum of antimicrobial activity, do not leave toxic residues, are unaffected by water hardness, are inexpensive and fast acting, remove dried or fixed organisms and biofilms from surfaces, and have a low incidence of serious toxicity.
NaDCC (Sodium dichloroisocyanurate) should be the preferred one. Use of powder/granules should be more than liquid preparations in view of significant differences in storage requirements, shelf life and potency.
Sodium hypochlorite (‘bleach’) should be the last choice, if other chemicals are not available. Hypo is unstable and the disinfection efficacy of the final prepared solution varies widely. If used, it should be procured within one month of the manufacture and used as soon as possible. The can label should mention manufacture and expiry dates, batch number and concentration (minimum 5%).
Disadvantages of hypochlorite include corrosiveness to metals in high concentrations (>500 ppm), inactivation by organic matter, discolouring or “bleaching” of fabrics, release of toxic chlorine gas when mixed with ammonia or acid (e.g., household cleaning agents, urine), and relative stability. In general solid powders with these contents should be preferred over liquid hypochlorite.
These groups of disinfectant chemicals have carbolic acid base, derived from coal tar. Chlorinated fraction and petroleum residues are added to improve their cleansing and physical properties. Usually they are black or white fluids.
Phenolics are mostly used for floor and wall cleaning and can also be used for hard surfaces and equipment that do not touch mucus membrane (e.g. IV stands, wheel chairs, beds etc.)
They are more potent than iodophors. They are irritant to skin and mucosa and corrosive to metal surface. White fluids are emulsified suspension and precipitate on surface and make subsequent cleaning difficult.
Phenolics are not recommended for use in nurseries and food contact surfaces.Although this is a traditional disinfectant, it is damaging to the environment. It is recommended that this chemical should be phased out as soon as possible.
The biocidal activity of aldehydes results from alkylation of sulfhydryl, hydroxyl, carboxyl, and amino groups of micro-organisms, which alters RNA, DNA, and protein synthesis. They have very good bactericidal, virucidal, fungicidal and sporicidal activity and are often used as HLDs. Aldehydes are generally non-corrosive to metal and do not damage lensed instruments, rubber or plastics.
Hydrogen Peroxide is popularly used in disinfecting equipment and environmental surfaces. It is effective against virus. Using this to clean blood from surfaces and linen is not recommended as it is very costly and corrosive. Can be used for cold sterilisation of heat sensitive critical items.Requires 30 minutes at 20oC. They are having rapid action and non-toxic.
There is no ideal disinfectant, and the best option should be chosen according to the situation. A disinfectant solution is considered appropriate when the balance between the antimicrobial activity, required disinfection level, toxicity of the product, ease of use and cost is satisfactory for the given application.
General Principles while Using a Hospital Disinfectant
Brooms should never be used in patient care areas.
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