High Level Disinfection (HLD)

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High Level Disinfection (HLD)
Disinfectants


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Please Note

• The following talk is an overview of disinfection
  and
• disinfectants. It is hoped that following this
  session you
• will encouraged to read further into this
  subject.
• I will not be discussing occupational exposure
  levels or
• disinfectant dilution strengths

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Topics

• Spaulding Classification
• Methods of Sterilization Disinfection
• Resistance of micro-organisms
• to HLD
• Chemical Disinfectants

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Methods of Sterilization

Physical agents
Mechanical removal methods
Chemical agents
Filtration
Gases
Liquids
Heat
Radiation
Dry
Moist
Steam under pressure
Hot Air Oven
Ref MAC (UK2002)
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Disinfection and Sterilization

• SPAULDING believed that how a medical device
  will be
• disinfected depended on that devices ultimate
  intended use.
• CRITICAL (High)
• devices which enter normally sterile tissue or
  the vascular
• system or through which blood flows should be
  sterile.
• SEMI-CRITICAL (Medium)
• devices that touch mucous membranes or skin that
  is not intact
• require a disinfection process (high level
  disinfectionHLD)
• that kills all microorganisms but high numbers of
  bacterial
• spores.
• NON-CRITICAL (Low)
• devices that touch only intact skin require
  low-level
• disinfection.

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Critical (High) Patient Care Medical Devices

• Classification Critical (High) medical devices
  enter normally sterile tissue or vascular system,
  or through which blood flows.
• Object Sterility.
• Level germicidal action Kill all microorganisms,
  including bacterial spores.
• Examples Surgical instruments and devices
  cardiac catheters implants etc.
• Method Steam, gas, hydrogen peroxide plasma or
  chemical sterilization.

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Semi-critical (Medium) Patient Medical
Devices

• Classification Semi-critical medical come in
  contact with mucous membranes or skin that is not
  intact.
• Object Free of all microorganisms except high
  numbers of bacterial spores.
• Level germicidal action Kills all microorganisms
  except high numbers of bacterial spores.
• Examples Flexible endoscopes, rigid
  nasoendoscopes.
• Method High-level disinfection

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Noncritical (Low) Patient Medical Devices

• Classification Noncritical medical devices will
  not come in contact with mucous membranes or skin
  that is not intact.
• Object Can be expected to be contaminated with
  some microorganisms.
• Level germicidal action Kill vegetative
  bacteria, fungi and lipid viruses.
• Examples Stethoscope, tongue depressors,
• Method Low-level disinfection

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Classification of Risk
Risk Application Recommendation
High Items in close contact with a break in the skin or mucous membrane or introduced into a sterile body area Sterilization
Medium Items in contact with intact skin, mucous membranes or body fluids infected or immuno-compromised patients Sterilization or disinfection required.
Low Items in contact with healthy skin or mucous membranes or not in contact with the patient Cleaning
Ref Spaulding classification
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Definitions
Sterilization Validated process used to render a
product free of all forms of viable
micro-organisms
Disinfection Destruction of pathogenic and other
kinds of micro-organism by chemical means.
Destroys most recognised pathogenic
micro-organisms, but not necessary all microbial
forms, such as spores
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Disinfection
Cleanliness of device Presence of organic
matter
Disinfectant
Automated Washer Disinfector

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Resistance of micro-organisms to HLD
Most resistant

• Prions (TSEs)
• Spores
• Mycobactria
• Non enveloped viruses
• Fungi
• Bacteria
• Enveloped viruses

Least resistant

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Cautionary Information

• Disinfectants are not interchangeable, incorrect
  concentrations
• and in appropriate disinfectants can make the
  process ineffective,
• a danger to our patients and also result in
  excessive costs.
• Because occupational diseases among
  decontamination staff have
• been associated with the use of several
  disinfectants (formaldehyde,
• gluteraldehyde) strict PPE protocols are to be
  observed.
• Asthma and other respiratory diseases can occur
  in sensitised
• persons exposed to airborne chemical exposure.
• Risk assessment should be carried out, with the
  preferred method
• of control being elimination of the risk through
  use of an automated
• process.

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Cleaning

• Physical cleaning of the device prior to chemical
  disinfection must always be carried out
• lowers microbial challenge to the disinfectant
• removes barriers to disinfectant penetration
• removes substances that may inactivate the
  disinfectant
• Care must be taken that the detergent (cleaning
  agent) do not themselves inactivate the
  disinfectant / sterililant or react dangerously

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Chemical Disinfectants
A chemical disinfectant is a compound or mixture
which under defined conditions is capable of
destroying micro-organisims by chemical means.
Depending on exposure of the device to the
chemical will effect the level of disinfection
achieved (temperature, concentration) Usually in
the form of a liquid and occasionally gas Can be
supplied ready for use or may need accurate
dilution to appropriate strength Disinfectants
vary in their properties making correct choice of
disinfectant for a specific task important
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Spectrum

• Most disinfectants are capable of eliminating
  Gram-positive and Gram-
• negative vegative bacteria and enveloped viruses
  (sometimes referred to as
• lipophilic and hydrophobic viruses).
• Less easily eliminated targets are
• Non enveloped viruses (called hydrophilic
  viruses)
• Mycobacteria (particularly atypical mycobacteria)
• Protozoan cysts and spores

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Advantages

• Chemical disinfection is used mainly to reduce
  the risk of
• infection from equipment that would be damaged by
  the
• temperatures used in the more readily available
  sterilization
• processes. It allows relatively convenient rapid
  disinfection
• without high financial outlay on equipment.
• Chemical disinfection is often used for rigid
  type telescopes
• when there is insufficient time to allow other
  means of
• disinfection

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Disadvantages

• Disinfection by definition does not guarantee a
  sterile product as such it cannot be
• used for surgical invasive devices which are
  required to be free of all microbial
• contamination (sterile)
• Some chemical disinfectants can be toxic or have
  material incompatibilities
• Various factors can result in the failure of
  chemical disinfection. These
• include microbial resistance
• inactivation of disinfectant due to incorrect
  dilution
• inappropriate storage resulting in loss of
  efficacy
• equipment not cleaned sufficiently well prior
  to disinfection
• physical protection of the micro-organism due
  to tissue fixing (Cidex)

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Key Aspects of Endoscope Use
Health Safety of staff
Standards Guidance
Type of Endoscope Used
Infection Control / Patient Safety
Local Circumstances
Disinfectant Used
Reprocessor Used
There is no single system for the disinfection of
endoscopes and no single most appropriate
disinfectant
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Microbicidal Activity
Disinfectant Spores Mycobacteria Bacteria Viruses
Alcohol X vv vvv vv
Gluteraldehyde v vvv vvv vvv
Orth0-phthaldehyde v vvv vvv vvv
Other aldehydes v vvv vvv vvv
Chlorine Dioxide vvv vvv vvv vvv
Peracetic Acid vvv vvv vvv vvv
Other peroxygen compounds x v vvv vv
QACs x vv vv vv
Superoxidised saline vvv vvv vvv vvv
Key X None v Poor vv Moderate vvv Good
Least resistant
Most resistant
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Hierarchy of Control
Chemical Base Example of Product COSHH Hazard Group COSHH Controls Approach
Chlorine Base Sterilox A (Low Hazard) 1 (General Ventilation)
Chlorine Base Tristel A (Low Hazard) 1 (General Ventilation)
Peroxygen Virkon S (1 liquid) A (Low Hazard) 1 (General Ventilation)
Peracetic Acid Nu-Cidex / Aperlan C (Medium Hazard) 3 (Containment)
Ortho-phthalaidhyde Cidex OPA C (Medium Hazard) 3 (Containment)
2 Gluteraldehyde Cidex E (Special Case) 4 (Special Case)
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Disinfectants Key Differences
Disinfectant Base Properties Examples
Alkylating agents Superior materials compatibility Higher COSHH Hazards / Controls Group Micro-organisms can become resistant to gluteraldehyde Ability to fix protein may limit use of some products Glutaraldehyde (Cidex, ASEP, Totacide) Ortho-phthaladehyde (OPA) (Cidex-OPA) Mixtures (Gigasept rapid, Septo DN)
Oxidising agents Superior sporacidal activity Lower COSHH Hazards / Controls Group May be incompatible with some endoscopes Chlorine containing compounds (Tristel) Peroxygen compounds (Virkon S) Peracetic Acid (Nu-Cidex, Steris, Aperlan)
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Glutaraldehyde - Cidex

• Advantages
• Numerous use studies published
• Widely used disinfectant
• Relatively inexpensive
• Excellent materials compatibility
• Disadvantages
• Respiratory irritation from vapour
• Pungent and irritating odor
• Relatively slow mycobactericidal activity
• Coagulate blood and fix tissues to surfaces
• Allergic contact dermatitis

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Glutaraldehyde - Cidex
Contraindication

• Strict environmental controls
• Withdrawn from UK market by manufacturer
• Occupational asthma
• Dermatitis
• Advances in disinfectants with superior bacterial
  activity
• Glutaraldehyde chemically related to formaldehyde
  and has similar toxic effects
• Cross link residual protein material

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Ortho-phthalaldehyde Cidex (OPA)

• Advantages
• Fast acting High Level Disinfectant
• Better bactericidal and myobactericidal activity
  than glutaraldehyde
• Excellent materials compatibility
• Not a known irritant to eyes and nasal passages
• Weak odor
• No environmental limits
• Recommended daily use of OPA test strips

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Ortho-phthalaldehyde
Contraindication

• Repeated exposure to OPA may have resulted in
  hypersensitivity in some patients with a history
  of bladder cancer undergoing repeated cystoscopy.
• Urological procedures - reports of patients who
  have experienced anaphylaxis-like reactions
  after repeated cystoscopy (typically after 4-9
  treatments).
• Risk control measures residues of OPA minimized
  and contraindicated for reprocessing of
  urological instruments used on patients with
  history of bladder cancer.

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Inadvertent Misuse

• OPA is often inadvetentantly diluted during use.
  And studies
• have shown OPA declined after a few days of use
  when using
• OPA chemical baths when disinfecting
  naso-endoscopes.
• The decline in affectivity occurs because
  instruments are not
• thoroughly dried and water is carried in with the
  instrument,
• which increases the solutions volume and dilutes
  the effective
• concentration

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Peracetic Acid - Oxydising Agents
Example of products Aperlan (Lancer) contains
hydrogen peroxide Nu-Cidex Perascope Steris

• Numerous peracetic acid based disinfectants on
  market
• Good sporicidal effects
• Medium COSHH hazard assessment
• Requires containment
• Agents may be single shot or reusable
• Test strips available for reusable
• Can effect cosmetically the finish of metallic /
  anodised components

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Chlorine Based Electrolysed Acid Water
Sterilox

• Mixture of active elements derived from salt by
  electrolysis through an electrochemical cell
• Basic materials saline and electricity
• Biologically friendly - non toxic
• Expensive system requires generator
• Intended to be used as fresh solution but tests
  indicate active up for up to 48 hrs
• Can cause damage to silicon cover of insertion
  tube sticky / pitting
• Sterilox provides protective wipe
• Users must carry out daily pre-use checks of
  endoscopes

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Biocidal Action Chlorine Dioxide

• Chlorine Dioxide
• is an oxidising biocide. It deactivates micro
  organisms by
• attacking and penetrating their cell wall,
  disrupting the transport
• of nutrients across the cell wall by inhibiting
  protein synthesis.
• This action occurs regardless of the metabolic
  state of the
• organism, oxidising biocides are effective
  against dormant
• organisms and spores

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Biofilm - Chlorine Dioxide

• The low oxidation potential of chlorine dioxide
• allows penetration of biofilm. Very effective in
• water treatment
• Effective treatment of biofilm
• In terms of legionella control chlorine dioxide
  is
• proven effective against cysts that form in the
• biofilm.

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Advantages Chlorine Dioxide

• Effective against biofilm build up
• Broad based disinfectant
• Non irritant to skin or mucus membrane contact
• Non carcinogenic
• Environmentally safe breaks down to salt
• Fast acting 30 seconds to 5 minutes depending
  on which product is used
• Multi-use / single shot use

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Chlorine Dioxide - Tristel

• Tristel products
• Tristel Multi-Shot
• Tristel 1 Day
• Tristel One-Shot
• Use of Tristel may cause blistering of outer
  insertion sheath
• Recommend use of conditioning wipe provides
  protection to sheath
• Key Med has no objections to its use
• Tristel Sterile Wipes available for
  non-lumended instruments
• Recently introduced Stella automated
  disinfection system

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Endocavitary Probes

• Telescopic Examination Probes
• Transoesophageal echocardiography probes,
• vaginal/rectal probes used in ultrasound Scanning
• Rigid type endoscopes (not being introduced into
• sterile cavity - nasoendoscopes)
• Telescopes in contact with mucous membranes are
• semi-critical UK Royal College ENT
• recommendation

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Ideal Disinfection Method

• Highly efficacious
• Rapidly active
• Strong penetrability
• Materials compatibility
• Non-toxic
• Organic material resistance
• Adaptability
• Monitoring capability
• Cost-effective

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