My experience working with 60+ other CRNAs at a level 1 trauma center has taught me that many tend to push their basic knowledge way back in their brain. For some it becomes a distant memory of what once was, Storm Anesthesia and recertCRNA are now launching a "Back to the Basics" for CRNAs. We cover may of the topics that are our basic foundation of what we do every day. Although, CRNAs become very good as safely taking care of patient under anesthesia, I do find that many a CRNA lack the same full understanding of what is happening as they once did. 

All this is quite understandable, since studies show that humans seem to "forget" a significant amount of learning very quickly. What does that mean? Do we actually forget the information, or do we just need a bit of extra prodding to remember? 
Much has been studied about children and summer learning loss (SLL), which is documented when children return back after a three month summer vacation. Is this actual loss, ie, the students no longer have any idea what they learned just prior to their vacation?
This is very doubtful. Much more likely is that not focussing on the newly learned material over the summer, now requires a bit of puzzle work to make the memories of how it all works return. Then when it does come back it often leads to greater understanding of the material.