Well, if you look at CRNA programs, most are very selective and require you to have ICU experience, usually 2 years. Your "fastest" option is going to take you quite some time no matter. Figure however long it will take to get your BSN (obviously only you and your school knows how many credits you need to get your BSN), then pass your boards, Secure a job in ICU, work for 2 years, apply to CRNA school (they usually start interviewing a year before starting), 24-36 months for CRNA (average 28) then boards, so you're talking around 8 years if you start now. One step at a time, need to do your RN first. Good luck.