The cardiac ICUs that I've worked in are 1:1 for fresh post-ops, super-sickies, pts with VADs/IABPs and CVVHD; 2:1 for stable pts. The staffing in the teaching hospital I work for now (I just came back here, but this is where I've spent most of
my nursing career) was always enough to allow for 2:1 assignments, at worst.
The PRIVATE hospital I worked for until a couple weeks ago was an entirely different story. Except for the CVICU, they staffed a certain number of nurses - period. Acuity is not a factor. Everyone had 2:1 assignments if the unit was full and
fully staffed, but if someone called out, a they would triple up the assignments - totally unsafe IMO.