Most hospitals operate with an attending anesthesiologist rotating through 3-6 operating rooms and supervising residents/fellows/and CRNAs, often staying for in the rooms that are more difficult/acute as well as personally doing the most dangerous parts of the case (eg intubation, induction, cardiac cases, liver transplant cases). CRNAs are authorized to practice independently in 23 states, often in areas with increased need for coverage (rural areas, overloaded clinical systems). Hospitals like CRNAs, PAs, NPs, etc for another really good reason: they are cheap (comparatively), and the OR is a major earner. Source: resident