I have a question about autoclave hold times. As far as I am aware, hold time is defined as the time from the last thermocouple reaching the required temperature (in this case 121.1°C) until the end of sterilisation/exposure. This should exceed 15 mins in this case.
Some thermocouples are slower to reach temperature, meaning the 15 mins is not achieved when sterilisation ends. However, this is a liquid load, and the contents retain heat after the end of sterilisation. When this is included, the contents are exposed to 121.1°C for >15 mins. Is it acceptable to include temperatures recorded during the cooling phase? Or must the 15 mins be achieved during sterilisation?
I’m not an expert in sterilization but I would not recommend using time outside the sterilization phase in your hold time. Once the sterilization phase is over, the autoclave will begin to cool down and you cannot guarantee that liquid temperatures will always maintain 121.1 for the required amount of time. I am surprised that it takes the liquid a while to reach temperature, maybe you should adjust your preconditioning/heating phases to make sure the liquid heats to 121.1 sooner to the start of sterilization.
Good luck,
Ronyace
Hi
I would suggest you refer the PDA report on Validation of Steam Sterilizers and it clearly suggests that you should consider the lethality from 100 Deg till it cools down to 100Deg . The reason being that during the come up time you deliver significant amount of lethality which is sufficient enough to kill some bio burden and thus we need to consider the same during the cycle. Also the concept of 15min is not important because its the lethality which you deliver is important rather then the time because lethality kills the bio burden and not the time even though they have the same units.
[quote=AnkurSalesworth]Hi
I would suggest you refer the PDA report on Validation of Steam Sterilizers and it clearly suggests that you should consider the lethality from 100 Deg till it cools down to 100Deg . The reason being that during the come up time you deliver significant amount of lethality which is sufficient enough to kill some bio burden and thus we need to consider the same during the cycle. Also the concept of 15min is not important because its the lethality which you deliver is important rather then the time because lethality kills the bio burden and not the time even though they have the same units.[/quote]
I agree with Ankur, it is not recommended that you include that time. Because you cannot prove that the temperature gives you enough lethality every time. I guess we gotta think the lethality during come up and cool down time as a bonus kill. And it always better to have a overkill than an under kill just to be on safe side.
One of the reasons (for not reaching the temperature fast) I can think of is if the vials are not sealed properly after inserting the TC it would loose pressure from the vials and it would never reach your sterilization temperature. So you gotta figure out a way of sealing them properly.(I had this problem with my 2ml vials autoclave validation where the TC’s never reached the sterilization temperature)
or may be you can try to increase your cycle time.
Hi,
May I know what type of thermocouple are you using i.e. J, K, T or E type ?
I would recommend using K-type as it has minimum response type (in milliseconds).
Secondly, I agree with other posts for prevention of liquid escape if the vial/ampoule is not sealed properly.
Regards,
HTM 2010 should not agree with your first point of 121.1, it should be more than 121.5. Because all the thermocouples accuracy may be within -0.5 °C to +0.5 °C.
If u set your sterilization cycle parameters as pre heat at 115.0 and 120.0 for certain time, it is easy to reach all the probes 121.5.
with Regards,
Sitarama Raju
Oncology Unit