I had my Nissen three and a half years ago. Before my Nissen my asthma was out of control due to reflux effects on my lungs, and I had been on high doses of steroids...both inhaled, and at times, orally.
Because of this I had developed adrenal insufficiency, and my doctors recommended a steroid boost for my surgery. Honestly, I didn't notice a thing. I guess it would have been something I'd have noticed if they hadn't done it, because from what they said I might have gone into shock because of the stress caused by the surgery.
They gradually weaned me off the steroids over the next couple of weeks, and I never noticed any problems at all.
Good luck with your surgery!
Words of wisdom by Eckhart Tolle:
"Whatever you fight, you strengthen, and what you resist, persists.”
“Worry pretends to be necessary but serves no useful purpose”
“Accept - then act. Whatever the present moment contains, accept it as if you had chosen it. Always work with it, not against it.”