Jumping ship can be difficult. I would keep my plans underwraps until you absolutely must declare...to your IM faculty. People are very invested in their own field and often feel a sense of betrayal when someone changes. This can negatively impact your evaluations. Honestly, you do not have to tell anyone your ultimate career plans...but do NOT lie about it either. This is a difficult question because I do not advocate "hiding" things from others. At the same time, I am realist and understand that you not broadcasting your career plans is your choice and frankly it often necessary given politics and prejudice. Remember the classic med-school interview question about primary care vs subspecialty? You have a right and should insist that how you are judged is based on objective & some subjective "standards of performance" and not on prejudice.
When I matched in a Cat-spot in surgery this year, my PD met with all the interns and told them this was me "dis-owning my family". I have since had people not willing to discuss medical management decisions and often use the statement, "it doesn't matter to you because your a surgeon now".
In all of this, the first two groups that came knocking on my door was Rads & anesthesia both which recruited me heavy from within my institution where I was doing my GSurge prelim. Neurosurgery also put out some feelers but I was not really interested so they didn't waste anymore time.
Complete your ERAS application, then arrange a private meeting with the anesthesia PD and discuss you plans, goals, and especially your concerns about potential retaliatory evaluations. He/she will be willing to tell you how they recommend you approach this and how long they will be able to keep things under wraps. I know it is not uncommon for anesthesia residencies to actually have a spare Cat spot specifically held for people jumping ship from surgery and the like.
Having said that, make sure you work hard in IM and be "the best IM intern" they have ever seen. Do not give them amunition or reason to start freezing you out. Do NOT allow your interest in a change next year affect your learning this year or your patient care. Honor the contract you have this year to your fullest potential...do not sign the IM PGY-2 contract until after:
1. you didn't match
2. you have decided not to scramble
3. you have decided to honor that PGY2 contract
As for letters of recommendation, if you have a month or more of ICU this year, you might get to work with an anesthesia attending...take advantage of that.
Good luck, it is a difficult spot to be in
