Power
Sure, the surgeon is the head honcho in the operating room, but if you don't keep those organs out of the way while they're trying to make a cut, there could be some serious problems. As highly-trained as a surgeon may be, they only have two of those skilled hands. They needs yours so that they can do their best to achieve optimal results for the patient. Yours is the power to help make that happen.
That said, you also have to follow the surgeon's orders—every order, every time, no questions asked. It's not often that the "matter of life or death" cliché applies literally, but it definitely does in this profession.
So, yeah, if by power you mean things like influence, autonomy, or the ability to take an hour long nap in the middle of the day just because you feel like it, you most certainly won't be finding power like that as a surgical assistant. But if by power you mean the power to literally help save lives, all day, every day, then yeah...you've got power.