While you are in college, it definitely doesn’t matter what kind of doctor you want to be. You will probably decide that either during medical school or as a first year resident (your first year after medical school). It is only after that that you go on for more specialized training.

As far as going from being an RN to being an anaesthesiologist, it is possible, but not an easy transition. You may get many of the science classes you need for medical school while you are in nursing school, but nursing school is by no means the same as medical school. You would still need to go to medical school to become a physician before you can be an anaesthesiologist.

The test to get into medical school is called the MCAT.