Can't comment exactly how surgery may change it but if you are taking any antibiotics, that sure will do it. It will make the hair dry and very brittle, so be sure to moisturize, moisturize, moisturize. A few years ago, I had a bout where my hair started shedding very bad. I used to go to the hair salon every week and had to miss one week and the shedding was getting worse and worse and I was trying not to stress (until I could see her again and show her exactly what i was talking about) cause I know that wouldn't help.
When I got back to see my stylist, she started with a list of questions (trying to troubleshoot) and when I told her I was taking some antibiotics, she told me that was the culprit. I want to say she may have said something to the effect that surgery will do to your hair, but I didn't pay close attention at the time since it didn't apply to me, but I hope someone else will chime in and give their experience. Or you may even ask your doctor when you go for a follow up visit. At least you will know so you can go on and counteract and treat the problem.
Good Luck....