The chances of adverse reaction are very minute and easily handled by staff who have protocols in place. Report any weirdnessess to the nursing staff immediately. Otherwise sit back and relax and perhaps even chat with your neighbour - met a lot of good people while in the lazy boy! As Fall Colors points out, water is good - it will also assist your nurse with getting a nice fat vein on the first try. The first time I received Remicade 10 years ago (also for fistulas), I did so with absolutely no side effects and within a year was in full remission. It was a god send!
I've most recently had a need for a 2nd use of Remicade but may have developed antibodies and may have to discontinue the med. FYI...the most typical 'delayed' reactions reported are flu like symptoms or muscle and joint pain - usually between Day 4 and 10 following infusion. They can be easily mitigated by rest and/or over the counter meds. Any such reaction should be reported to your doc right away though and definitely prior to your next infusion. I in fact had this type of reaction on this my second go round with Remicade - most likely for antibody reasons - and although the delayed reaction was not fun, I assure you it was very tolerable in the big picture.
All the best!