Validating autoclaves for medical waste disinfection- a ... · Autoclave overheating Caused bags to...

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

Thank youMore information fromrstringer@hcwh.org

www.noharm.org