So I do surgical neurophysiology/neuromonitoring for brain and spine procedures and nearly all of my cases are with CRNAs. Typically, the anesthesiologist will come in with the patient (along with the CRNA) and assist with getting the patient to sleep and intubated, then positioned onto the operating table. After that they leave and go assist with other cases or do whatever it is they do, leaving the CRNA in the OR to administer the case. 99% of cases have no issues, and the anesthesiologist may pop his head in a few times throughout the case to see if the CRNA needs anything. Another CRNA may stop by to give a break. Then, at wake up after the case is finished, you might see the anesthesiologist, but maybe not. That's a typical case.

If ANYTHING goes wrong, they call the anesthesiologist immediately while trying to correct the issue. This could be something like an irregular BP, suspected issues with a leak in the airway, IV or art line issues, or something as serious as pulmonary edima during extubation.