Instrument Processing, Sterilization and Disinfection
Instrument Processing
The processing chain
Instrument processing is a serial chain in which each link protects the next: transport in a closed labeled container (never loose in a pocket); cleaning to remove bioburden; rinsing and drying; inspection; packaging with an internal chemical indicator; sterilization; and storage that keeps packages dry and intact.
Spaulding classification
- Critical (surgical instruments, bone, scalers entering tissue): must be sterile.
- Semicritical (mouth mirrors, amalgam condensers, handpieces contacting mucosa without penetrating): sterilization preferred; high-level disinfection only if heat-sensitive.
- Noncritical (housekeeping surfaces): low-level disinfection.
Traps
- Sterilizing without cleaning. Coagulated blood and debris shield organisms, and no sterilizer penetrates bioburden. Skipped cleaning is the most commonly tested error.
- Handpieces. They require cleaning, lubrication per manufacturer, and heat sterilization between patients - not surface wipe-down alone.
- Brushing instruments in open air or under high-pressure running water, which aerosolizes contaminants; use a submerged scrub or a lidded ultrasonic.
- Assuming a wrapped package carries a fixed expiration date. Event-related shelf life applies: the item stays sterile until the wrapper is compromised.
Rule of thumb
Dirty to clean, clean to sterile. Never let a clean instrument touch the dirty side of the sink, and never package or store a wet instrument.
Sterilization and Disinfection
Sterilization methods
Steam autoclave (121 °C at 15 psi for 15 minutes, or 132 °C for about 4 minutes), dry heat, unsaturated chemical vapor, and ethylene oxide or hydrogen peroxide systems for heat-sensitive items. Match the biological monitor to the method: Geobacillus stearothermophilus for steam; Bacillus atrophaeus for dry heat and ethylene oxide.
Three levels of monitoring
- Mechanical and physical - gauges, time, temperature, printouts.
- Chemical indicators - external process indicators and internal integrators; they show exposure to the process, not sterility.
- Biological indicators - spore tests, the only direct verification of lethality. Run at least weekly and with every load containing implants.
Biological failure
Stop using the sterilizer, recall every item processed since the last documented negative biological, reprocess, service the unit, and require consecutive negative tests before returning it to service. Document the event.
Disinfection
Use EPA-registered products at the labeled dilution and contact time. High-level disinfectants (glutaraldehyde, ortho-phthalaldehyde) serve semicritical items that cannot tolerate heat; test glutaraldehyde with minimum-effective-concentration strips and comply with PPE and ventilation requirements.
Traps
- Treating a color-change chemical indicator as proof of sterility.
- Using flash cycles for convenience or for items that will be stored.
- Assuming a glutaraldehyde solution lasts its labeled life regardless of how much has been processed in it.
Rule of thumb
The biological indicator is the referee. When one fails, the recall line is drawn at the last documented negative biological - not at the last load that looked acceptable.