I think my P100 filters might survive an autoclave. They are the pink disc kind from 3M. Pressure cooking only goes up to 121C @ 15psi, so it isn't as hot as it may seem.

It's not just the pressure and the temperature, it's also the steam. Autoclaves are are pretty nasty environments, and I wouldn't trust a filter that had gone through one. It's very likely the filter medium would have been degraded.