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Validating autoclaves for medical
waste disinfection- a case study
Ruth Stringer
International Science and Policy
Coordinator
Health Care Without Harm
SIGN meeting, Dubai, Nov 2010
Advantages of autoclaves for
medical waste disinfection
� Familiar technology in hospitals
� Reliable and economical
� Available in many sizes and levels of sophistication
� Can easily test them, prove they are working effectively
The need for validation
� Only a small proportion of autoclaves- usually large ones- are specifically designed for waste
� Manufacturers’ settings may not be the most efficient
� Waste is often in plastic bags, hard for steam to penetrate.
� May be more than one waste stream (eg mixed waste and syringes) with different treatment requirements
� Create standard operating procedures
Parameters to consider
� Waste type� Syringes, mixed waste, sharps, etc
� Waste containment, � plastic bags, cotton bags, dressing drums
� Waste placement within autoclave� check disinfection happens in coldest parts
� Best temperature to use
� Pulses to get steam into waste
� Unique properties of the machine in question
� Final destination of the waste after treatment
UNDP/GEF guide to autoclave
testing
� For routine testing of autoclaves after validation
� http://gefmedwaste.org/
Bir Hospital project
� 350 bed hospital in Kathmandu, oldest in Nepal
� No proper disposal route for waste, so it has been disposed with municipal waste
� Recently installed autoclaves for waste disinfection
� HECAF conducting assessments, training and leading the implementation process, including segregation and recycling
� HCWH providing technical support
� WHO SEARO provided funding for the validation
Autoclaves
� 2 x 175 litre horizontal autoclaves
� Gravity displacement
� Same model used in other hospital departments
Basic test procedures
� Fake medical waste and date-expired syringes used for experiments
� Test materials attached to teflon pole for easy retrieval
� Insert into middle of waste container
� Where possible, test every container
� ALWAYS test the container in the coldest spot
Steam integrators
� Similar to autoclave tape
� Change colour after a specific time at the sterilisation temperature
� Cheap, instant result
� Complement but cannot replace biological indicators
Biological indicators
� More expensive, slower to give results than
integrators
� The best test of efficacy
� Contain heat resistant
bacterial spores
� Incubate for 24 hours
� Any surviving spores will grow and turn the solution
yellow
Temperature and pressure
monitored manually
Manufacturers’ technical support
� Read the manual- but don’t depend on it completely
� Rarely gives enough detail
� Often hard to understand- mixture of technical language and translation issues
� Manufacturers’ technical back-up very important� Expect to have questions the manual cannot answer
� This project had good manufacturers’ support
� Issues with this project� Pressure gauges were wrongly labelled
� Limited set of run cycles available to normal users
� Needed password to reprogram autoclave
� Local engineers did not know how to reprogram autoclave
Choice of temperatures
� Usually 121oC or 134oC for small-scale machines
� 134oC generally regarded as better� Quicker disinfection time time: 8 vs 15 minutes
� Plastic bags can melt at higher temperature� HDPE widely used, most grades melt at 120oC-130oC� Autoclavable bags (PP), often too expensive
� Need to consider the whole cycle� In our case, 16 minutes to go from 122oC to 134oC
� Most of the kill time at 122oC already completed� Quicker and more energy efficient to work at 122oC
Pressure pulses
� Used in autoclaves without vacuum pumps
� Flushes out air
� Gets the steam deep into the waste
� Eliminates air pockets
� Increases level of steam saturation
�Steam saturation level a factor in disinfection
efficiency
Autoclaves have pulses too, and
sometimes skip a beat� Pulse cycle was pressure drop, followed by steam injection
� But with no vacuum pump, the first pulse was not effective
� Had to programme autoclave for one more pulse than we wanted
Bir Hospital Autoclave validation Exp.No 13
Autoclave 1, syringes
Run parameter: Pulse: 4, Sterilization temp-1210C, Sterilization time-20 minute
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Temperature Centigrade Chamber pressure Kg/cm2 Jacket pressure Kg/cm2
Waste containment
� Plastic bags� Most widely used
� Poor steam penetration
� Most common material, PE, melts at high temperatures
� Cotton bags� Used to hold many small bags of waste
� Better steam penetration
� Robust and reusable
� Dressing drums� Designed for autoclaving
� Best for syringes
� No chance of penetration if needles are accidentally left on
Infectious medical waste� Plastic bags placed into cotton bag
� Necks of plastic bags left open for better steam penetration
� Allows steam in better than plastic, may reduce sticking
� Cotton is reusable, washable
Syringes
� Tested and rejected idea of plastic or cotton bags
for syringes
� Autoclaved in a drum in
case of uncut needles
� Two drums fit in the autoclave
� Can autoclave 9-10 kg syringes at one time
Autoclave
overheating
� Caused bags to melt and stick to autoclave walls
� Originally thought to be due to operation at 134oC
� Still seen at 121oC, but only in one autoclave
� Could have been caused by faulty temperature OR pressure control
� Solved by adjusting jacket pressure
Power cuts, dirty waterBir Hospital Autoclave validation Exp.No 4
Autoclave 2
Run parameter: Pulse: 3, Sterilization temp-1210C, Sterilization time-20 minute
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Power cuts, dirty water
� Water is processed bore water, sometimes dirty
� Hardness can cause scale buildup, clog pipes and valves
� Dirt can clog valves, water level sensor espvulnerable
� Flush water tank regularly� to avoid salt buildup and
dirt affecting operation
� Bir Hospital has guaranteed electricity supply, avoids load shedding that affects most of city
� Power cuts still occur
� Resume program after short outage
� Restart after longer outage
Timer problems
� Autoclave clock went backward
� Question- was it recording error?
� Enhanced monitoring proved problem was real
� Problem caused by software errors
� Machine also only counting time at steady state
� Manufacturer will be updating software
� Later experiments timed against clock instead of
autoclave timer
Enhanced monitoring regime
Summary
� 24 experiments with 2 autoclaves
� Final cycle 4 pulses, 30 minutes at 121oC� effective for mixed waste
� Also disinfects inside syringes, important if they are to be recycled
� Standard operating procedure� Operation and maintenance log
� Manufacturers will be updating their software
� Hospital will be testing all the rest of their autoclaves
