let me see If I understand... no swans IABP... but vents and vasoactive drips? There is more to know... how often do you take rule out MI's? Do you keep 2 or 3 patients ready for stepdown but there are no beds? Do you take all the hospital codes?
it seems you'd need a nurse staff of 5, 3RN's 2 lpn's and be able to flex on high acuity days to 6 nurses preferably 4RN's, 2 lpn... Some of these seems easy to tripple, as I've had 3 stable vents... 4 vents in a PCU setting... long term.. low dose dopa and dobut... maybe some cardizem. But you have an interesting mix creating assignments

I would not ever work less than 5... unless I'm not understanding your patient population and assuming a higher acuity.