At the time of this writing, there is no official FDA Guidance Document detailing allowable particulate from medical devices. You can imagine that this would be an issue especially in blood-contacting applications. Particulate escaping into the vasculature can ultimately accumulate in the brain, occluding small vessels and leading to ischemic stroke. At the very least, insoluble particulates will accumulate in the lymph nodes where they may just hang out forever, participating in a life-long chronic immune response in much the same way those ink particles in your tatoo are doing.
Word reaching my ears from the street is that the FDA is concerned about particulate in medical devices and is asking companies who are developing catheters and other blood contacting devices to run particulate tests. Since there is no official medical device particulate test, it looks like they are requesting USP 788.
USP 788 is actually a test for particulates in injectible formulations. It involves streaming a liquid exudate from a device through a sensor that can count the particles, usually with a laser. Some of the newer equipment used for this can even "see" clear particles and count them. For medical devices, it looks like the FDA is specifically asking for "Tes
t 1B" in the USP 788 document, which is a test for particulates in a container with a nominal volume of 100 mL. The allowable limits are also given in the document.
For those that sell or use hydrophilic coatings, this is something to look out for. I dare say you should even design this requirement in ahead of time, even though it is not official yet. I believe that in the future there will be a medical device coating requirement on particulates.