You MUST have at least one year in a critical care unit. CRNA school is competative, so the more experience the better. Also, once you start working in said unit, you will realize how valuable that year is. No matter how great your school is, you don't learn how to be a nurse until you ARE one. And CRNAs are nurses that know their ****. They are the "right hand man" in the OR. Different states and facilities have different rules regarding the anesthesiologist part of your question. You don't necessarily have to work FOR an anesthesiologist, but you certainly have to work WITH one. In my hospital there are 5 OR suites, 5 head CRNAs, and 3 anesthesiologists. The docs hop from suite to suite, but they trust the CRNAs to do their own thing.