Ch.9 Instrument Preparation, Antisepsis and Disinfection Flashcards
How long does Staphylococci live on scrubs - 60% cotton 40% polyester blend
1- 19 days
How long can Stephylococci and enterococci live on pure polyester
> 90 days
How should surgical clothing be washed to remove significant quantities of microorganisms according to the US Centres for Disease Control
160F/70C
50-150 ppm chlorine bleach
How should surgical clothing be washed to remove significant quantities of microorganisms according to the European Norm BS EN
80C for at least 10mins
or
60C for 60 mins - without reuse of the rinsing water
What does sterilisation refer to
Complete destruction
or elimination of
vegetative bacteria,
bacterial spores,
viruses and fungi
by physical or chemical methods.
Disinfection refers to
Many or all microorganisms are eliminated except bacterial spores
Disinfectants
Applied to inanimate objects
May be toxic to living tissue
The efficacy of disinfection and sterilisation is influenced by
- Organic/inorganic load present
- Instrument type
- Level of contamination
- Presence of biofilm
- Material of the object
- Concentration and exposure time of the chemical
- Temp & pH of the disinfection process
Critical items - definition, cleaning process, example
Definition: Penetrate the soft tissues, enters or contacts the bloodstream/sterile tissue.
Process: Clean, Disinfect, Sterilize
Example: All surgical instruments
SemiCritical items - definition, cleaning process, example
Definition: Contact mucous membranes or non intact skin, does not enter bloodstream/sterile tissue.
Process: Clean, High level Disinfect
Example: Endotracheal tubes, endoscopes
NonCritical items - definition, cleaning process, example
Definition:Contact skin but not mucous membranes
Process: Clean, Disinfect
Example: Stethoscope
Final processing of instruments should be performed within what time frame
6 hours
How does increasing water hardness affect cleaning of instruments
Reduces the effectiveness of blood removal in cold water prewashes
What is an acceptable alternative to manual cleaning
Prerinsing in an enzymatic cleaner
Some only req 2-10mins contact time
mjority need 30-45 at room temp
Advantages of Hydrox
Combines cleaning with microbial killing
This protects health care workers from infectious risks and reduces bioburden on instruments
Ideal pH of detergent solution
Neutral
Best material compatibility
Good soil removal
What should instruments be rinsed with after cleaning
Deionised water
Which has been shown to be more effective, automated cleaners or manually cleaning
Automated
How do ultrasonic cleaners work
High frequency vibratory waves which clean through cavitation and implosion
Waves of acoustic energy are propagated in aquous solution.
Disrupts air pockets ensuring thorough wetting
What must be done with the instrumenst following ultrasonic cleaning
Rinsed with demineralized water
Why is rinsing of instruments after cleaning essential
Cleaning fluid could result in endotoxin contamination of surgical instruments which may cause severe inflammatory rxns in tissues
Does ultrasonic cleaning provide any antimicrobial activity
No but it can act synergistically to increase bactericidal efficacy of a disinfectant
How do automated washer disinfectors disinfect instruments
Heat disinfection
Automated washer disinfector run through
- Cold rinse
- Main clean - product neutralization - 55C
- Rinse
- Disinfect - 90-93C for 5 mins
- Dry cycle
For a machine connected to tapwater with a hardness of 25 and incoming temp of 15c the cycle would take 54mins
What is an Ao value
Time equivalent
Number of seconds temp has reached **80c **or more
Measure of expended energy
temp/time
Disinfection over what Ao value is deemed highly secure
> 5000Ao
Ao value of the automated washer disinfectors
5985
Ao value of household diswashers
285
Least effective wrapping materials
Cotton and linen
<30days
Cautions when using packaging that contains cellulose
Not compatible for hydrogen peroxide gas plasma steriliation
Aluminium containers allow safe storage time of how long
Up to 1 year
How long should instruments rest before packaging and at what temp and humidity
Room temp 20-23c
30-60% humidity
2 hours min
Storage time, open shelf and closed cabinet
Single-wrapped muslim (2 layers)
Open shelf - 2 days
Closed cabinet - 7 days
Storage time, open shelf and closed cabinet
Double-wrapped muslim (2 layers each)
3 weeks - open shelf
7 weeks - closed cabinet
Storage time, open shelf and closed cabinet
Single-wrapped crepe paper
3 weeks - open
8 weeks - closed
Storage time, open shelf and closed cabinet
heat sealed paper and transparent plastic
At least 1 year - open/closed
What tests can be used to detect residual contamination of processed instruments
ATP bioluminescence
Why are biological indicators superior to chemical indicators
Measure the effective microbial killng power of the sterilization process
The spores used are more resistent and greater in numbers than are commonly found on surgical instruments
What does SAL describe
The probability of an item being non sterile afer it was exposed to the sterilization process
SAL of medical devices
10 to the minus 6
1/1,000,000
Difference between how dry heat and moist heat kill
Dry - oxidation and dehydration
Moist - Irreversible denaturation of enzymes and critical proteins
Typical sterilization cycle
Exposure time - 20mins at 121c for a SAL of 1 in 10,000
For each additional 2 mins at 121c SAL decreases by a factor of 10
Estimated bioburden on surgical instruments
1000
How do most autoclaves work
Gravity displacement
steam pressure drives air downward
Drying time in autoclave
15 - 30 mins
What is flash sterilization
Item is placed in an open tray
Rapid penetration of steam
eg 3 mins at 132c in prevacuum autoclave
Flash sterilization is contraindicated in what instruments
Implants
Highest tolerated leak rate of steam sterilizer
1mmHg/min
Test to prove air removal and steam penetration within dense packaging are complete
Bowie-Dick
Temp, pressure, time for sterilization of glass, porcelain, metal or porous items using steam
Steam heat: 121-124c
200kPa-2.0 atm
20 mins
SAL 10,000
134-138c
300kPa-3atm
5 mins
Temp, pressure, time for sterilization of glass, porcelain, metal or porous items using dry heat
160c
180mins
170c
80mins
180c
30mins
Temp, pressure, time for sterilization of wrapped instruments and textiles items using steam
121c
200kPa 2.0atm
30 mins
132c
200kPa 2atm
25 mins
SAL 1,000,000
Draw backs of using LTS - Low Temp Sterilization
Inneffective against proteins and salt residues
Once lumen drops below 3mm - decresed efficacy
How does ethylene oxide work
Alkylating agent
innactivates DNA and RNA
effective against vegetative bacteria, fungi, viruses, spores
Highly flammable - usually mixed with Freon or CO2 to reduce flammability
EtO (ethylene oxide) sterilization process
- Pre conditioning & humidification
- Gas introduction
- Exposure
- Evacuation
- Air washes
2.5 hours
What can reduce effectiveness of EtO below lethal point
Water/condensation
What is better at sterilizing vetwrap, steam or EtO
EtO
How long should an implant ve aerated post EtO prior to use
2 weeks
For how long should instruments be allowed to aerate at room temp following EtO
7 days
to avoid tissue toxicity
Mechanical aeration of EtO in gas sterilizers
8-12 hours at 50 - 60c
Advantages of hydrogen peroxide gas plasma
Short instrument turnaround time 50-75mins
No health hazards
Low temp <50c
Safe for heat and moisture sensitive instruments
How does hydrogen peroxide gas plasam sterilization work
Aqueous solution of hydrogen peroxide injected into the chamber
Converted to gas plasma by radio waves
Create an electrical field
Vapor converted to free radicals
Collide with and inactivate microorganisms
Instruments not suitable for gas sterilization with Hydrogen Peroxide
Flexible endoscopes
Items derived from plant fibers; linens, gauze, cast padding, tongue depressors
Effective liquid sterilization system for heat sensitive, complex design flexible endoscopes
Steris System 1E
Table top
25mins
Steris System 1E Liquid sterilization process
Water is filtered,
UV sterilized and
Mixed with Steris S40 concentrate - mix of 40% acetic acid, 35% peracetic acid, 6.5% hydrogen peroxide
Solution is circulated in chamber of machine
Pumped through endoscope chanels
What is high level disinfection
Chemical exposure times insufficient to achieve sterilization
but
sufficient to inactivate all microorgs except spores
FDA definition: Sterilant used for a contact time that obtains a 6-log10 kill of a Microbacterium
Trade name, action, effect, disadvantages of Isopropyl alcohol
Trade: Propanol
Action: Protein dentaturation
Effect: Bactericidal, effective against vegetative bacteria only
Disadvantages: Poor against spore, fungi, viruses, cytotoxic in tissue
Trade name, action, effect, disadvantages of Propan-2-ol, Propan-1-ol
Trade: Sterillium
Action: Protein dentaturation
Effect: Bactericidal, fungicidal, effective against many important viruses,
Disadvantages: Cytotoxic in tissue
Trade name, action, effect, disadvantages of Ethanol 96% and Biphenyl-2-ol
Trade: Desderman pure
Action: Protein dentaturation
Effect: Bactericidal MRSA, fungicidal, effective against many important viruses,
Disadvantages: Cytotoxic in tissue
Trade name, action, effect, disadvantages of glutaraldehyde
Trade: Cidex, Omnicide, Abocide
Action: Protein & nucleic acid dentaturation
Effect: Bactericidal, fungicidal, viricidal
Disadvantages: Long 10 hour exposure time for sporocidal effect, limited shelf life once activated, Cytotoxic in tissue
Trade name, action, effect, disadvantages of Chlohexadine
Trade: Nolvasan
Action: Cell membrane disruption and cellular protein precipitation
Effect: Bactericidal, fungicidal, variable viricidal
Disadvantages: Not sporicidal
Trade name, action, effect, disadvantages of Povidone-iodine
Trade: Betadine
Action: Metabolic interference
Effect: Bactericidal, fungicidal, viricidal
Disadvantages: Poorly sporicidal, some inactivation by organic debris
Trade name, action, effect, disadvantages of 1.Octenidine and
2.Polyhexamethylene biguanide
Trade: 1.Octenisept
2.Lavasept
Action: Cell membrane disruption
Effect: Bactericidal, fungicidal
Disadvantages: Not sporicidal
Glutaraldehyde GH is affective against
Broad spec antimicrobial - bacteria, fungi, viruses, mycobacteria
Low conc 0.1% - inhibits germination of spores
High conc 2% - sporicidal
Deactivates teteanus toxoid
Mode of action of GH
Binds to outer layers of microorganisms
Alkylation of sulfhydryl RNA, DNA and protein synthesis
GH is more active in alkaline or acidic solutions?
Alkaline
pH 7.5 - 8.5
but high pH shortens its shelf life
When should GH soltion be considered unsafe
Test indicates dilution of 1-1.5% GH
Disadvantages of GH
Can produce biofilm
Corrosive
Tissue toxicity
How to dispose of GH
Neutralise with Sodium bisulfate first
Cidex as a steriliant - time and temp
25c
10hours
Cidex as a high level disinfectant
25c
45mins
Cidex as an intermediate level disinfectant
20-25c
10min
OPA - how long to destroy all common bacteria
5 mins europe
10 mins canada,australia
12 mins usa
at 20c
Advantages of OPA
No noxious gas,
no activation req
compatible with all materials
does not coag blood or fix tissues to instruments
stable at pH 3-9
Disadvantages of OPA
Decreaed suscpetibility to P. aeruginosa
Irritant to resp tract/eyes
Stains inc skin
Anaphylactic rxns
Succindialdehyde is recommended for
Flexible endoscopes, us probes
Liquid formalin contains what % formaldehyde
37%
What does formaldehyde kill and how
Bacteriacidal
Tuberculocidal
Fungicidal
Virucidal
Sporicidal
Alkylates amino and sulfhydryl groups of proteins and ring nitrogen atoms of purine bases
Formaldehyde-alcohol vs formaldehyde
Formaldehyde-alcohol - steriliant
Formaldehyde - high level disinfectant
Mode of action of peractetic acid PAA
Oxidizing agent
Denature protein
Disrupt cell wall
Oxidate sulfhydryl and sulfur bonds
PAA vs GH
PAA- Cidex 0.35% Steris 0.20%
PAA similiar to better biocidal efficacy
Contact time 10-15 mins
Conc 0.09%
Inativte G+, G- bact, fungi, yeasts in <5mins at <100ppm
Effective against mycobacteria 20-30mins at 0.26% even with organic load
Less health risk
Does not create biofilm
Less stable than GH
Corrosive
Carcinogen
Dull aluminium
Action of Hydrogen peroxide
Hydroxyl radicals - attack membrane lipids, dna, cellular components
Hydrogen peroxide is better against G+ or G-
G+
% of H202 required for sterility
6-25%
% H202 for cleaning medical devices
0.5%
Conc of household bleach
5-6%
Cidex OPA - Peracectic acid - activity
All microorgs minus spores in 20 mins
Virkon - Peroxygenic Acid
Foot baths/mats
Cant destroy endospores and molds in practical timeframe
What are the most potent antiseptics
alcohols
Alcohols bacteriocidal or static
cidal
optimum conc of alcohol
60-90%
if 100% less bactericidal - needs water to denature proteins
The antimicrobial activity of alcohol is influenced by what
Length of its carbon chain and branching
Rank the bactericidal efficay of alcohols
n-propanol>isopropanol>ethanol
which alcohol is strongest against viruses
ethanol
Alcohol in combination with povidone iodine
Potentiates the antimicrobial effect by increasing release of free iodine
Mode of action of chlorhexidine
TARGETS CYTOPLASMIC MEMBRANE
causing precipitation or coagulation of protein and nucleic acid
Injures the outer membrane in G- and cell wall in G+
Is not sporicidal but prevents development by inhibiting outgrowth but not germination
Efficacy of chlorhexidine against viruses
Effective against enveloped but not against naked viruses ie rota, aden, entero
At 1-2.5ug/ml chlorhexidine acts as bacteriststic or cidal?
Bacteriostatic
20ug/ml req for bacteriocidal
Chlorhex lacks activity against what bacteria
Some G-
Pseudomonas
Providentia
(unless combined with edta)
at 4% lacks activity against Enterococcus
Toxic effects of Chx gluconate
Highly ototoxic
High damaging to cornea
Anaphylactic shock
Advantages of Iodine
Most effective agent against MRSA
Fast acting at low conc so little resistance
Mechanism of action of Iodine
Penetrates cell wall causing disruption of protein and nucleic acid structures
Betadine composition
10% sol with 1% iodine
Iodine in sol with polyvinylpyrrolidone
(PVP-I2)
only 0.8ppm free iodine as binds to PVP so may not be sufficient
DILUTE WITH H20 TO FREE IODINE
Surface contact time to release free iodine from PVP-I2
At least 2 mins
Which are more effective against spores, water mixtures or alcohol mixtures of iodine
water mixtures
Up to what % PVP-I2 can be used on the cornea
10%
available as a 5% opthalmic sol
Use of pvp-i2 in eyes as tx
irrigation of conjunctival sac with a 5% sol of comparable efficacy as a 3 day course of topical abx
Mode of action of Octenidine
Interacts with polysaccharides in cell wall and cytoplasm of microorganisms - leakage of cytoplasmic membrane and cell death
Benefits/Risks of pHisoHex
Prolonged residual activity
Not adversely affected by organic material
Neurotoxic from dermal exposure
Polyhexamethyene Biguanide PHMB is widely used in what
wound dressings as low cytotoxicity against keratocytes and fibroblasts
repeat exposure of p. aeruginosa to 5mg/L chx resulted in what
Increase MIC fromn 10-70mg/l within 6 days
