Pat ~
Because you'll be unconscious, you'll be completely unaware of the hours you'll spend in the OR during your surgery. Just as when you go to sleep at night and wake up in the morning not knowing what happened while you were asleep. In the OR, you'll be 'hooked up' to many monitors including a 'nerve monitor' and the usual blood pressure, pulse rate, oxygen rate monitors. Although I didn't have one, the spinal catheter is a precaution and not uncommon. A urine catheter is standard, as Jan noted. I had one but it was inserted after I was 'under' the anesthesia (unconscious) and it's removal (48 hours later ) was quick and painless. Many AN surgery patients experience nausea immediately following the surgery, which is usually brought on by the anesthesia. Anti-nausea medication is available. and will be given to you, if necessary. The nausea usually subsides on it's own within a day or two of the surgery. A post-op headache can occur but again, the hospital will supply medication to combat this - if it occurs. You'll awake with a large head-bandage but that is usually removed within a few days. Most of the possible problems you may experience immediately post-op will resolve within a few days. You shouldn't have any serious pain but you will very likely feel fatigued. My advice is to sleep as much as you need to. I did...for a day or so, until I felt better and began to get restless lying in bed all day. I believe this is typical for AN surgery patients. This is major surgery and while it has consequences, most are handled fairly well by AN patients and of course, you're in a hospital - an ICU for the first day or so - and help is always nearby. The kinds of monitors in the OR will also be used to monitor your 'vital signs' while you're in the ICU.
Frankly, this is an experience where you absolutely must have faith in your doctors and trust them (and the hospital staff) to do what is best for you. Constant anxiety and worrying can't change a thing but it can induce unnecessary stress that you really don't need right now. I suggest that when your surgery day arrives, you 'let go' and just allow the professionals to do their work, which is for your benefit. Yes, there may be some problems post-op but that is unknowable now and worrying about things that may never happen is futile. Some discomfort has to be expected with a surgery such as this but within a few days, most of it passes and you'll likely be home again and on the mend before you know it. Try to think positive and not focus on 'what-ifs' and things you cannot control. I would also suggest that you have a talk with your doctor and ask him some of the questions you've posed here. He can probably offer you more precise information that may also help to calm your anxiety.
Jim