This is my 2cents worth. I'm not the best but I strive to be the best.
Look at his reason/s why he's in there for. I would say that you need to look at things on the whole rather than just one, as this will need some experience and skills. I believe you will get there. I would say that always keep a look out for his hypertension (HP), as he may have it as an ongoing condition (secondary to whatever condition it may be). Hmmm, does he have a stoma to begin with? Does he have a drainage? and much more.. As this questions are in a nurses mind once he comes out of Theatre. That's the reason I said, to see things on a wider aspect rather than just one. Assessment of patient is utmost important role for a nurse to do, especially from a start of a shift to the end of the shift.
It's a good question you have there, but we kinda needed a little more info. Remember this, no question is a silly question. It is important to ask. It will take experience to be able to tell a patient's condition by their medication/s, and their overall outlook.
So back to your question... If he is in pain, his HP will increase, if you feel that he'll be constipated, request for a laxative on the second day to help his bowels... that is if it is not contraindicated too. Observer whether does he have a drainage? Observe for internal bleeding from BP, and so on. Therefore, it is an overall view again. See the point?
Don't take everything on your plate for now, do things step by step, as you are still learning. Keep up your good work. You did a great job by asking too. Well done. Keep your head up, be on your toes when patients just came back from the Operation Theatre, and the list goes on.
I hope this help your question. Take care for now. ;P