I work 3 12 hours shifts a week in general as do most nurses on my unit. A few on my unit work 5 8 hr shifts. We all take 1-3 days off on call a month with weekday call from 4pm-7am and weekend 24 hours.
At my hospital the Anesthetist work day shift 5 days a week and they rotate call with a doc and CRNA on call daily. We have 3 CRNA and 3 perm docs and some locum so they get call a couple of times a week. The CRNA on call comes in and does any OB stuff but if the OR is open 2 of them have to be in-house so they work lots.