I've been doing IVIG monthly for over 10 years and I do best at 100 ml/hr. Benadryl is also an excellent suggestion. I use it every evening after my infusion.

Don't try to analyze the electrolyte/fluid balance. You are screwed up because of IVIG, plain and simple. Hydration flushes out the screwy bits...just go with it. : ) A nutritious diet never hurts anything either.

Hope you're feeling better soon.