Problems with PET G During ETO Sterilization

Temperature test kit - Thermal Tape This might work, but I don't think it tells duration, don't know.

They also make tape that turns black it a specific temperature is reached. It is non-reversible.

Thank you Lyn! As a matter of fact we use "steri dots" which are indicators that turn from red to green when product has been sterilized. This time I am afraid we need something more "fancy", cause the problem may be hidden in different stages of the entire process

Forgot to say: This problem happens in a random way affecting more or less a 10% of the trays. We purchase PET rollstock and do the themoforming in house. PET is purchased in large quantities (about 2,000 kg) twice a year always to the same provider.

We are also considering defects in the PET like lower fusion points affecting part (spots?) of the rolls (which should have been seen during thermoforming), and already contacted the supplier for this product. We also are testing trays simulating the ETO process

Have you thought about going down the route of irradiation? normally 25 - 50 Kgy is enough to sterilize everything and the product shouldnt then heat up.

Hello only1yeti! yes, we have considered irradiation, BUT there is a problem: the content of the trays is a 2 components PMMA (Acrylic surgical bone cement). One component is a powder (polymer), the other is monomer (fluid). Radiation produces a hardening (self polymerization) of the fluid, and ageing of the powder, which drastically reduces shelf life of the product.

it might be worth purchasing a few Temptale monitors (google temptale there is a variety of different ones) atleast it would constantly monitor the temperature during the process and allow you to see any hot spots etc.

The pictures should be helpful.

Are these heated in an oven? How big is the chamber; how many trays will the oven hold at one time? Does the contractor have any data about uniformity of temperature within the oven? What is the heat source? How does your contractor monitor the process for deviation? What process controls are implemented?

The trays are used multiple times? Do you know if older trays seem more likely to have melt spots? Does this seem to be as likely on first time trays are used?

Can you tell if the melt spots are influenced by how the instruments are packed into the trays? Is there only one way to pack the instruments? Can instrument placement perhaps be an influence?

What happens after the trays are removed from the sterilization procedure? Are they placed where they may receive heat from another source? Are they exposed to anything which might lead to embrittlement? How are the trays transported to and from the contractor? Could they be overheated during transport?

These are just questions from a quick brainstorming session I held with myself wondering where you might uncover sorces of variation.

Hello Reward! trays are sterilized in a sterilization chamber measuring around 10 Sq.Meters. This chamber is hermetically closed, as the process not consists in elevating pressure, then heat, later-on release of ETO and finally a degassing takes place. Chamber remains closed until complete degassing of the product has taken place. This happens between 5 and 10 hours after end of process. Products are conditioned in pallets, measuring about 1 SM. Usually we sterilize simultaneously one truck load a week. Process is made in accordance to strict specific ISO norms. This considers even distribution of all the variables required for the process (heat, gas, etc). Validation of the process is performed on a regular basis, using state of the art monitoring equipment (as indicated in the norm). Products are not in contact with heat sources during transport.

I in the past for temperature sensitive sterilization needs have used and recommended using plasma in conjunction with peroxide. Sterrad is one that comes to mind that utilizes this methods for critically temperature sterilization applications.

our concern is acutally because this is a problem we did not have before (by now, it´s 20 years doing the same process! ) Peroxide is not allowed for uor products, therefore my concern in solving this issue asap. Thank you!

20 years with no problems is a good run. However, something has changed at that facility. It may be as simple as someone retired and now whatever he was doing is not done or done differently. More than once have I seen a change traced back to the new person who was doing as they were trained but still found a way to add variation.

Hello Iris, thanks for your input! I will search for these Omegalabels, and have them distributed inside blank trays. This will help us to search for "hot spots" that may cause the problem we have been experiencing. On the other hand, if they prove to be reliable, we also can use them from now on in order to have one more control of the process. This will take a bit more time because we will have to do a validation process of these labels in a certified institute. The second step will be to make changes in our Quality -Assurance System and get the approval from the CE Notified Body we have our products registered at in the European Community. In the meantime we already had requested a meeting with the Quality guys from the sterilization company in order to get this problem solved. This will probably imply a complete validation of their sterilization process as well as of all their control equipment.

The good news is that (due to the high, and increasing costs) of the outsourcing for sterilization, 6 months ago our company bought a ETO chamber, which will be operative at our plant in about 8 weeks. By now we have 2 teams doing the training and certifications at the manufacturers facility for operating it. We already hired a specialist who will be in charge of this plant.

The datalogger you mention seems to be very interesting as well: I will discuss this issue with the supplier of our chamber, cause I have the feeling it may be of interest.

Thank you again!

It is definitely worth pursuing the causes at your sterilization supplier even though you will soon be performing this in house. I look at it this way, your current supplier may have uncovered a problem your in-house operation might also experience. Might as well start your Lessons Learned for your process now.