My Baby Gets A SEVERE Diaper Rash Every Time After

My baby gets a SEVERE diaper rash every time after going under anesthesia. Is this normal? How long should it last? What can I do to help it? I've tried Gold bond powder, diaper rash cream, lotrimin, Vicks vapor rub. It still hurts him so badly we can barely hold him. He bawls his eyes out the entire time we're changing his diaper. I NEED HELP!