2. Manual mechanical cleaning, distant from the bedside, with full submersion in water and detergent while physically wiping all exterior surfaces and brushing the accessible inner channels. This requires flushing and aspiration of large volumes of water and detergent followed by a thorough rinse. Detergents facilitate disaggregation and removal of debris but are not efficient microbicides. Some automated endoscope reprocessors (AERs) employ a validated “brushless” cleaning process prior to disinfection cycles.
3. HLD of all exposed surfaces via full submersion and perfusion through all lumens using an approved LCG and appropriate parameters for concentration, temperature, and duration of contact. HLD can be achieved with prolonged passive soaking in appropriate LCG solutions; however, data suggest greater shortfalls in meeting requisite parameters and greater risk of inadequate bacterial clearance.12
4. Rinse with sterile or filtered water or tap water, followed by alcohol flush of all accessible channels (umbilical cord, biopsy, elevator cables) to evacuate residual LCG and water, thereby facilitating complete drying. This step is usually automated and accomplished by most AER machines.
5. Forced air drying to ensure complete removal of moisture from the endoscope channels.
6. Upright storage in clean, dry cabinets away from flow of ambient microorganisms. Straight upright storage theoretically facilitates drainage of any potentially retained liquids. Varieties of specialty cabinets with filtered or heated air flow, and some with flat storage, are marketed for this purpose.
HLD performed with careful adherence to validated manufacturers’ instructions for use (IFUs) results in clean endoscopes with remarkably low risk of residual clinically important contaminants. Adequate reprocessing of gastrointestinal endoscopes, however, is hampered by several specific challenges, including: (1) the immense bioburden they acquire during use, (2) the relatively narrow margin of safety achieved when all reprocessing steps are appropriately performed, (3) the risk for development of intractable biofilm when cleaning steps are insufficiently performed, (4) the lack of rapid and accurate bio-indicators of the process end points, (5) training, support, and ongoing supervision for staff who performs the repetitive tasks, and (6) the need for efficient turnaround of instruments in busy clinical environments.
Following use, endoscopes commonly harbor 106 to 109 microorganisms. Following combined precleaning and manual cleaning, endoscopes enter HLD with a bioburden of about 101 to 105 microorganisms.13,14 HLD achieves a further 6 log (106) reduction, culminating in a theoretical terminal bioburden of 10–6 to 101 organisms per instrument.15 While this is generally well below the inoculum required for detrimental clinical effects, any shortcoming or hindrance to optimal performance clearly risks shortcomings in the terminal cleanliness and safety of the instrument. Failure of the initial precleaning and cleaning steps risks the development of adherent biofilm, which cannot be reliably removed or sterilized with repeated optimal performance of standard HLD. Reliable, inexpensive, rapid biomarkers to assess adequacy of reprocessing by assaying for residual contamination would clearly improve performance and cleaning outcomes. No such indicators exist, however. A variety of indicators for residual blood, protein, and other components of living tissue have been evaluated, but none appear reliable for assessment of the fully reprocessed instrument.16 Testing for ATP, which is present in all living cells, is widely used in food preparation and cleaning industries, but ATP results obtained from reprocessed endoscopes do not correlate with terminal culture results.17 Gross differences in ATP levels are evident between well-cleaned and poorly cleaned instruments, prior to HLD, so it may prove useful as a check on training and monitoring of performance by cleaning personnel.18
6.2.3 Liquid Chemical Germicides and Automated Endoscope Reprocessors
Multiple LCGs are available for reprocessing of flexible endoscopes (
Some LCGs are consumed with each reprocessing cycle, but many are labelled for reuse, defined by time intervals or cycles of use in automated reprocessing machines. Repeated reprocessing cycles dilute the LCG, eventually risking decline in concentration below their minimum effective concentration. Agent-specific test strips should be employed to monitor LCG concentration over time. Manufacturers’ IFUs should be followed regarding frequency of testing, generally per procedure.
AERs are designed to automate a variety of tasks formerly done manually during HLD. They enhance consistency in many parameters of reprocessing cycles (time, volume, temperature, pressure, concentration, etc.) and enclose LCGs and contain their fumes, thus limiting exposure of staff to potential irritants. Several are labelled to accomplish washing by vigorous perfusion of detergents prior to HLD.21 The FDA and manufacturers have advised that this function does not replace manual washing for duodenoscopes and echoendoscopes. All AERs provide HLD, generally by complete submersion and vigorous channel flushing of appropriately-timed cycles of LCG followed by thorough rinsing. Most proceed with automated alcohol flushing and at least initial air flushing. Many AERs record and document the endoscope, LCG, and cycle parameters during performance. Compatibility between endoscopes, LCGs, and AERs should be ensured and the IFU should be closely followed to avoid risk of insufficient HLD cycles, chronic microbial contamination of machines, and staff exposure to reprocessing agents.
Table 6.3 Liquid chemical germicides commonly employed in gastrointestinal endoscope reprocessing as high-level disinfectants or chemical sterilants
| Agent | Advantages | Disadvantages |
| Glutaraldehyde | • Long experience, numerous studies• Inexpensive• Good materials compatibility | • Respiratory irritation• Pungent and irritating odor• Slow mycobactericidal activity as sole agent• Coagulates blood and fixes tissue to surfaces• Allergic contact dermatitis |
| Hydrogen peroxide | • No activation required• Does not coagulate blood or fix biomaterial to surfaces—may enhance removal of organic matter• No disposal issues• Inactivates cryptosporidium | • Material compatibility concerns• Serious eye damage with contact |
| Ortho-phthalaldehyde (OPA) | • Fast—shorter reprocessing cycles• No activation required• Odor not significant• Excellent materials compatibility claimed• Does not coagulate blood or fix biomaterial to surfaces | • Stains protein gray (skin, membranes, clothing, etc.)• Higher expense than glut• Eye irritation with contact• Slow sporicidal activity• Anaphylactic reactions to OPA in bladder cancer with repeated exposure during cystoscopy |
| Peracetic acid | • Low-temperature liquid chemical sterilization | • Potential material incompatibility |
| Peracetic acid–hydrogen peroxide | • No activation required | |
| Source: Data from Rutala and Weber.20 | ||
6.3 Transmission of Infection by Gastrointestinal Endoscopy
A 2013 compilation of known outbreaks of infection attributed to interpatient transmission during gastrointestinal endoscopy in the United States and Europe identified 47 clusters of cases involving 235 patients, including 19 outbreaks in upper endoscopy (56