2 interviews a week apart...how do I delay an answer?

I currently have a job on orthopedic/med-surg floor, but I have two interviews coming up. The first is in two days (PACU/day surgery), the second is 6 days after the first interview (stepdown). My question is, if I get an offer from the first interview before I take my second interview (or before a few days after the second interview, to allow the second interview people a little while to make up their minds), how do I delay an answer to the first interview until I know the results of the second interview? Is there a way to keep my options open without losing an offer from the first interview?

I think that I may want the PACU job with the first interview the most, but that I may have a better shot at getting the stepdown job (second interview). I'd be glad to take either job, though.

(FYI: I work at a hospital system which has 4 different hospitals; my current job is within the same hospital system as the two interviews, although at a different hospital physically; and the two interviews are both at the same hospital. That is to say, the results of my interview/offer may be open-access/casual word-of-mouth to the interviewers, as well as to the higher-ups at my current hospital.)