Reprocessing Flexible and Rigid Laryngoscopes:

May 1, 2005

Reprocessing Flexible and Rigid Laryngoscopes:


Are Quaternary Ammonium Disinfectants Adequate?

By Lawrence F. Muscarella, PhD

Laryngoscopes
are one of several different types of rigid and flexible endoscopes sometimes
referred to as ENT (or ear-nose-throat) endoscopes. Examples of flexible
laryngoscopes include rhinolaryngoscopes and nasopharyngo-laryngoscopes.
Rhino-laryngoscopes use fiber-optic or video technology to examine, diagnose and
evaluate the normal physiologic and pathologic conditions of, among other
organs, the larynx. Most models are used for diagnostic procedures and do not
have any internal channels. Some models, however, feature a single working
channel, a suction control valve, and a biopsy inlet port that can be used for
aspiration, removal of foreign objects, and performing biopsies.
Naso-pharyngo-laryngoscopes are similar in design and function to
rhino-laryngoscopes. Rigid laryngoscopes, on the other hand, are used to expose
and view the larynx to facilitate endotracheal intubation. These endoscopes
feature a fiber-optic disposable or reusable blade that is available in
different sizes, may be curved or straight and connects to the laryngoscopes
handle.


Classification of Medical Instruments

Before it can be determined whether selection of a quaternary
ammonium product is appropriate for cleaning and disinfecting rigid and flexible
laryngoscopes, it is first necessary to evaluate the risk of nosocomial
infection associated with the use of these instruments. Application of a widely accepted three-tiered classification
scheme for medical instruments aids in the evaluation of this risk. According to
this scheme, medical instruments that penetrate sterile tissue, enter the
vasculature, or contact the patients blood are classified as critical
instruments, because the risk of nosocomial infection associated with their use
is high.1-4 (See Table 1.)

Semi-critical instruments, on the other hand, contact
mucous membranes or non-intact skin, but do not typically penetrate sterile
tissue (see Table 1). The risk of nosocomial infection associated with
instruments in this second category, while still potentially significant, is
markedly less than the risk associated with critical instruments.
Rhinolaryngoscopes, naso-pharyngo-laryngoscopes, and the blades and handles of rigid laryngoscopes are classified in this second
category.1-4 Medical instruments that either do not directly contact the
patient or only contact a patients intact skin pose a low risk of nosocomial
infection and therefore are classified as non-critical instruments (see
Table 1).1,2 Most environmental surfaces, including walls, floors and sink
tops, are included in this third and low-risk category.


Sterilization and the Three Levels of Disinfection

Once the risk of nosocomial infection associated with the use
of rigid and flexible laryngoscopes has been evaluated and their classification
as semi-critical instruments understood, a review of: published endoscope
reprocessing and infection control guidelines; the definitions of sterilization
and disinfection; and the labels of quaternary ammonium products is necessary to
determine whether they are sufficiently effective to satisfy the minimum
reprocessing standards required to prevent rigid and flexible laryngoscopes (and
other semi-critical instruments) from transmitting disease.

Whereas sterilization is an absolute term and refers to a
process that destroys all types of microorganisms including high numbers of
resistant bacterial endospores, disinfection is a relative term and refers to
different types of processes that vary in effectiveness. As displayed in Table 2
in decreasing order of biocidal effectiveness, disinfection processes can be
classified into one of three categories, or levels: high-level disinfection
(HLD), intermediate-level disinfection (ILD), and low-level disinfection
(LLD).1-4 Each of these three levels of disinfection is, in effect, defined and
differentiated from one another by specific indicator microorganisms that
each respective level can and cannot reliably destroy. The relative
resistance of microorganisms to sterilization and the three levels of
disinfection is displayed in Table 3.1. The more resistant the microorganism,
the higher the level of disinfection (or sterilization) required to destroy it.

Defined as the highest and most effective level of
disinfection, HLD destroys mycobacteria (i.e., is tuberculocidal), viruses,
fungal spores and vegetative bacteria.1 HLD also destroys some, but not all,
bacterial endospores. It is the limited sporicidal activity of HLD that
distinguishes it from sterilization (which destroys all microorganisms,
including high numbers of bacterial endospores) and the other two levels of
disinfection (neither of which is sporicidal) (see Tables 2 and 3). Most
importantly, HLD destroys all pathogenic microorganisms encountered in the
endoscopic setting, including Clostridium difficile,
a spore-forming bacterium. (Almost all spore-forming bacteria are
non-pathogenic. Those few that do produce disease such as Bacillus
anthracis
and some species of the Clostridium genuseither
are destroyed by HLD or have not been associated with infection following
endoscopy.5

It is for this reason that differences in the infection rates
of rigid and flexible endoscopes subjected to sterilization or HLD have not been
documented.5 Liquid chemical sterilants (LCSs) are frequently used to achieve
HLD of endoscopes (see Table 2). LCSs that achieve HLD during short immersion
times typically are sporicidal and destroy high numbers of bacterial endospores
during long exposure times. One level below HLD is a less effective process known as ILD
(see Table 2).1 Whereas processes that achieve sterilization and HLD are
regulated by the Food and Drug Administration (FDA), ILDs (and LLDs) are
regulated instead by the Environmental Protection Agency (EPA). In general, ILD
destroys lipid or medium-sized viruses, most non-lipid or small viruses, fungal
spores, and vegetative bacteria. Like HLD, ILD is tuberculocidal. But what
differentiates ILD from HLD (and sterilization) is its inability to destroy
bacterial endospores, even during long exposure times. Examples of ILDs include
iodophor and phenolic compounds. Concentrated quaternary ammonium
cleaner/disinfectants may also be classified as ILDs. The third and lowest level
of disinfection, LLD, destroys fungal spores, vegetative bacteria, and lipid or
medium-sized viruses.1 But unlike ILD, LLD is not tuberculocidal (see Tables 2
and 3). Examples include diluted quaternary ammonium cleaner/disinfectants.


Selection of a Sterilization, Disinfection Process

For many reasons, selection of an appropriate sterilization or
disinfection process or technology for reprocessing a specific reusable medical
instrument (or environmental surface in the healthcare setting) is not always
straightforward. If every reusable medical instrument were constructed of
stainless steel and other durable materials not damaged by heat, pressure and
moisture, few reprocessing dilemmas would arise, and the simple and obvious, if
only, choice for reprocessing instruments would be steam sterilization. Indeed,
steam sterilization is the method of choice, because it is effective, fast acting, and
inexpensive.6

But the demand to improve patient morbidity, minimize the
invasiveness of surgery, and reduce healthcare costs, coupled with significant
advances in fiber-optic technology and materials engineering, spurned the
development of delicate instruments many of which are heat-sensitive and
arguably designed more to simplify complicated medical procedures than to
facilitate reprocessing. For these heat-sensitive instruments, several different
types of low-temperature sterilization and disinfection processes were
developed.

In addition to raising questions of materials compatibility,
however, some low-temperature sterilization processes may be less effective and considerably more expensive per cycle than steam
sterilization.6 Moreover, complicating selection of an appropriate
reprocessing process for a specific heat-sensitive reusable instrument, some
low-temperature sterilization processes have limited applications and are
contraindicated for reprocessing instruments with long and narrow internal
channels, such as flexible gastrointestinal endoscopes. Also, not every reusable
instrument requires sterilization. In many instances, disinfection is adequate
to prevent patient-to-patient disease transmission.

Although at times challenging, selection of an appropriate
reprocessing technology for a specific instrument can be simplified by
dovetailing the three-tiered classification scheme for medical instruments
displayed in Table 1 with the definitions and relative effectiveness of
sterilization and disinfection (see Tables 2 and 3). In general, critical
instruments, such as reusable biopsy forceps, require steam sterilization (Table
2).1,7,8 For heatsensitive critical instruments, such as some models of
arthroscopes and laparoscopes, a low-temperature sterilization process may be
indicated.1 (Refer to the sterilizers labeling and the instruments
reprocessing instructions regarding recommended processes, effectiveness and
compatibility.) Alternatively, if sterilization is not feasible, HLD is recommended.1

HLD is also recommended for semi-critical instruments
(although a low-temperature sterilization process may also be acceptable, as
well as steam sterilization if the instrument is not damaged by heat).1,7,8
Published guidelines emphasize that subjecting an arthroscope, laparoscope
(critical instruments) or a flexible endoscope (a semi-critical instrument) to
HLD instead of sterilization is acceptable and does not pose an infection
risk.1,5,7,8 In accordance with published guidelines, their classification as
semi-critical instruments (see Table 1), and their manufacturers reprocessing
instructions, HLD is recommended for rhino-laryngoscopes,
naso-pharyngo-laryngoscopes, and the blades and handles of rigid laryngoscopes (see Table 1).1-12

Finally, products that achieve ILD and LLD specifically,
general purpose cleaner/disinfectants approved for use in medical facilities
(see Table 2) are recommended for and limited to cleaning and disinfecting
non-critical instruments and environmental surfaces.1 (With very few exceptions,
ILD may be acceptable for a limited number of semi-critical devices, such as
hydrotherapy tanks, but not endoscopes. Refer to the specific instruments
reprocessing instructions.)


Quaternary Ammonium Products

Quaternary ammonium products (or compounds) are
broad-spectrum, EPA-registered, cleaner/disinfectants. Depending on their
concentrations, quaternary ammonium products intended for use in medical
facilities are labeled for ILD or LLD and therefore may be used to clean,
deodorize and disinfect non-critical items and hard, non-porous environmental
surfaces. In accordance with their labeling, quaternary ammonium
products may also be used to pre-clean critical and semi-critical medical
instruments prior to HLD or (sterilization). (Refer to the instruments
reprocessing instructions to ensure materials compatibility with quaternary
ammonium cleaner/disinfectants.)


Conclusion

Quaternary ammonium cleaner/disinfectants used in medical
facilities are labeled for ILD or LLD not HLD and therefore, while
indicated for cleaning and disinfecting non-critical items and environmental
surfaces, are contraindicated for flexible endoscopes. In particular, use of a
quaternary ammonium disinfectant to clean and disinfect rhino-laryngoscopes,
nasopharyngo- laryngoscopes, other types of flexible laryngoscopes, and the
blades and handles of rigid laryngoscopes is not an accepted practice,
potentially unsafe, and a violation of the standard of care. Cleaning using an
appropriate detergent (e.g., enzymatic detergent) followed by HLD at a minimum
is required for these semi-critical instruments as part of a complete and
validated reprocessing protocol.1-4,10-12 Use of quaternary ammonium products to
clean and disinfect surgical instruments has been linked to disease transmission.9

Further, although the handles of rigid laryngoscopes may not
always directly contact the patient, reports have demonstrated their
contamination with opportunistic pathogens.10 Published guidelines recommend
that these handles (and blades) be cleaned and subjected to HLD (or
sterilization)1-4,10,12. Steam sterilization of the laryngoscopes handle and
blade may also be acceptable, although flash sterilization may be
contraindicated. Review the laryngoscopes reprocessing instructions for a
list of compatible processes.


Lawrence F Muscarella, PhD, is the director of research and
development and chief, infection control for Custom Ultrasonics, Inc. He is also editor of The Q-Net Monthly
(www.myendosite.com). He can be reached via email at
editor@myendosite.com.



Table 1: Classification Scheme for Medical Instruments

Critical instruments:
Penetrate sterile tissue, enter the vasculature, or
contact the patients blood.

Examples:
Cardiac catheters, biopsy
forceps and implants.


Semi-critical instruments:
Contact mucous membranes or non-intact skin.

Examples:
Rhino-laryngoscopes,
naso-pharyngo-laryngoscopes, and the blades and handles of rigid laryngoscopes.1-4


Non-critical instruments:
Do not directly contact the patient, or only contact the
patients intact skin.

Examples:
Blood pressure cuffs,
stethoscopes and bedpans; and environmental surfaces, such as walls, floors and
sink tops.


Table 2: The Definitions, Characteristics and Relative
Effectiveness of Sterilization and Disinfection

(Sterilization or the level of disinfection appropriate for
critical, semicritical and non-critical medical instruments is listed)

Sterilization Destroys all microorganisms, including bacterial
endospores.
Sporicidal, tuberculocidal, virucidal, fungicidal and
bactericidal.
Uses bacterial endospores as biological indicators.


Examples: Pressurized steam,
ethylene oxide gas, hydrogen peroxide plasma.
Primarily used for critical instruments.


High-level disinfection (HLD)
Destroys all pathogenic microorganisms, including some bacterial endospores
during short exposure times.
Typically destroys high numbers of bacterial endospores
during long exposures times.
Sporicidal (limited), tuberculocidal, virucidal,
fungicidal and bactericidal.
Uses mycobacteria as indicators of effectiveness.


Examples: 2 percent glutaraldehyde,
7.5 percent hydrogen peroxide, 0.2 percent peracetic acid.
Primarily used for semicritical instruments.


Intermediate-level disinfection (ILD)
Destroys many types of microorganisms including mycobacteria.
Not sporicidal.
Tuberculocidal, virucidal, fungicidal and bactericidal.
May use mycobacteria, viruses as indicators of
effectiveness.


Examples: 70 percent isopropyl
alcohol, iodophor and phenolic compounds, concentrated quaternary ammonium
compounds (e.g., hospital cleaner/disinfectants with a tuberculocidal claim). Primarily used for non-critical instruments.


Low-level disinfection (LLD)
Destroys some types of microorganisms.
Neither sporicidal nor tuberculocidal.
Virucidal (limited), fungicidal and bactericidal.
May use the hepatitis B virus, HIV as indicators of
effectiveness.


Examples: Diluted quaternary
ammonium compounds (e.g., hospital cleaner/disinfectants without a
tuberculocidal claim).
Primarily used for non-critical instruments.


Table 3: The Relative Resistance of Different Types of
Microorganisms to Sterilization and Disinfection

(Listed in decreasing order of resistance of microorganisms to
sterilization and disinfection. In general, bacterial endospores and prions are
the hardest to destroy and lipid viruses are the easiest to destroy.)

Prions May require extended, multiple sterilization
cycles.
May be responsible for transmissible spongiform
encephalopathies.


Bacterial endospores Destroyed
by sterilization.
Some bacterial endospores can also be destroyed by HLD.*

Example: Bacillus stearothermophilus
Mycobacteria
Destroyed by sterilization, HLD and ILD.

Example: Mycobacterium tuberculosis

Non-lipid
or small viruses
Destroyed by sterilization, HLD
and ILD.


Example: the polio virus

Fungi
(molds and yeasts)
Destroyed by sterilization, HLD
and ILD.
Some fungi are also destroyed by LLD.

Example: Candida albicans

Vegetative
bacteria
Destroyed by sterilization, HLD, ILD and
LLD.


Example: Pseudomonas aeruginosa

Lipid
or medium-sized viruses
Destroyed by
sterilization, HLD, ILD and LLD.


Example: the hepatitis B virus, HIV
*HLD = High-level disinfection; ILD = Intermediate-level disinfection; LLD = Low-level disinfection


References:

1. Rutala WA. APIC guideline for selection and use of
disinfectants. Am J Infect Control. 1996
Aug;24(4):313-42. Review.

2. American Society of Anesthesiologists. Recommendation for
infection control for the practice of anesthesiology. (Second edition.), 1999:
http://www.asahq.org/publicationsAndServices/infectioncontrol.pdf

3. Assocition of periOperative Registered Nurses. Clinical issues. AORN
J
January 2000.

4. American Association of Nurse Anesthetists. Part III:
Infection Control Procedures for Anesthesia Equipment. Revised, 1997:
http://www.aana.com/crna/inf_control/infection_control.asp

5. Muscarella LF.
High-level disinfection or sterilization of endoscopes?

Infect Control Hosp Epidemiol.
1996
Mar;17(3):183-7. Review.

6. Muscarella LF. Are all sterilization processes alike? AORN
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7. Alvarado CJ, Reichelderfer M. APIC guideline for infection
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Infection Control. Am J Infect Control. 2000
Apr;28(2):138-55.

8. Garner JS, Favero MS. CDC guidelines for the prevention and
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control published in 1981. Am J Infect Control. 1986
Jun;14(3):110-29.

9. Centers for Disease Control and Prevention. Rapidly growing
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10. Simmons SA. Laryngoscope handles: A potential for
infection AANA J 2000
Jun;68(3):233-6.

11. Welch-Allyn. Operating instructions for the RL-150
Rhinolaryngoscope.

12. Rusch. Care and maintenance instructions for Rusch
laryngoscope