D.N.
I have not had this exact thing but a friend's nephew did. He had surgery at 9 months because the cyst on his brow was growing and affecting the bones. He is now 12 and totally fine.
My son had a port put in for medication he needs when he was 13 months. It does not matter how calm you are about the procedure or how much you know that your child will be fine. Once that day comes, you become a nervous, panicky MOM. They told me he would be in there about an hour but it took 2 1/2. At one hour, I started pacing. They had a little problem threading the line up to the vein in his throat so it took longer. When he woke up, he was totally out of sorts and screaming since he did not know why or what was happening.
Oh, I wanted to add for after. When he wakes up, he may not recognize you since he will be out of sorts. But remember, you are mommy and you will be able to calm him down and he will remember.
When my daughter had her tonsils/adenoids out at 4, there was a little boy maybe a year old. When he woke up he was screaming and crying, just like my son did. The parents totally panicked and swore they hurt him. The nurses tried to talk to them but they would not listen and tried to leave with him, still with an IV. The poor thing was scared even more. Just be calm and as he wakes up and recognizes things, it will calm down. I just want to say it is a totally normal reaction.