Disinfection of Medical Instruments
Classes of Instruments
Reusable medical instruments are divided into three classes for the purpose of determining the level of disinfection required (Spaulding Classification): critical, semicritical, and noncritical.
Critical instruments are those that penetrate normally sterile tissue, including blood vessels. Examples, in addition to surgical instruments and implants, include arthroscopes, laparoscopes, and endoscopic biopsy forceps.
Semicritical instruments contact mucous membranes or non-intact skin, but are not intended to penetrate sterile tissue. Examples include gastrointestinal endoscopes, cystoscopes, bronchoscopes, anesthesia and respiratory therapy equipment, vaginal probes used in diagnostic radiology, fitting diaphrams, flexible laryngoscopes, and the blades of rigid laryngoscopes. Items directly attached to instruments that contact mucous membranes, such as the handles of rigid laryngoscopes, should be considered semicritical instruments. Tonometers (used to measure ocular pressure) are also often not appropriately disinfected, resulting in outbreaks of epidemic keratoconjunctivitis.
Noncritical items are those that come in contact with only intact skin, and include blood pressure cuffs, linens, tourniquets, and general use equipment, furnishings, and environmental surfaces.
Critical instruments should be sterilized before reuse and semicritical instruments should be subjected to at least high level disinfection or sterilization, while non-critical items require only low or intermediate level disinfection prior to use.
Levels of Disinfectants
Sterilants destroy all microorganisms, including bacterial endospores. Examples of sterilants include pressurized steam, ethylene oxide gas, and hydrogen peroxide plasma.
High level disinfectants destroy all pathogenic microorganisms, including some bacterial endospores during short exposure times, and can destroy high numbers of bacterial endospores during long exposures times. Examples include 2% glutaraldehyde, 7.5% hydrogen peroxide, and 0.2% peracetic acid.
Intermediate-level disinfectants, labeled as tuberculocidal, destroy many types of microorganisms including Mycobacteria, but not endospores. Examples include bleach, phenolic compounds, alcohols, and concentrated quaternary ammonium compounds. These are also commonly used for disinfection of environmental surfaces, including blood spills.
Low-level disinfectants destroy some types of microorganisms, but not endospores or Mycobacteria. Examples include alcohols and diluted quaternary ammonium compounds.
Intermediate and low level disinfectants are not licensed for use in reprocessing critical or semicritical patient care equipment. The classification and disinfection requirements are shown below.
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| āBody Contact | FDA Deviceā | āDisinfection Requirements |
| āSterile site, vascular | Criticalā | āSterilization |
| āMucous membranes | āSemicritical | āHigh level |
| āIntact skin | āNon-critical | āLow level |
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