One thing to note is that when using caustics for light transport, you may want to help it out unless you can afford really long render times as many samples will be required to get it up to about correct brightness. Helping out means adding to whatever caustics is doing, so use with care as this is not energy conserving as far as shadows are concerned.
My initial general approach to such materials, is to start out with something like shown below. Since your model is properly double walled with internal features, it’s just going to be a pain to try to do any fresnel work on the shadows, so I’m ignoring it completely and just assigning a color. Since rough refraction is used, I chose to mix in a little translucency for shadow generation.
As you can see I’m using denoise data for the denoiser. I’m only at 25 samples, but a big number of counts for non diffuse samples. The end result looks like this with some personal tweaks (I can’t see anything with shadow catcher usage, lol) - this is only 25 samples and rendered in a little over a minute:
I’m not suggesting I’m close to your reference images. I’m just showing how I approach it. It’s the same setup for everything, just with some mix factors and roughnesses tweaked to some random value. Note that these kinds of materials are very hard to not only setup, but also to judge if you have one in front of you. Turbidity (fogginess) is one material property I haven’t been able to properly simulate in Blender. You might want to try some volume scatter for this, but I can never get close to where I want with this.
Other factors to consider; when using translucency like I am, diffuse is a related property that you might want to mix in. Maybe SSS is appropriate? Also, normals are untouched, as I figured for medical equipment you want it as smooth as possible to not pick up dirt. But you’d have to examine the real material, both the inside and outside as they may have different specifications.
That said, I’m glad I don’t have to work with these kinds of materials in my current job 