What was supposed to have happened when the narrator was six months old? What happened instead?

At six months, Junior had surgery. He was expected to die during the surgery, and if he managed to live, he was expected to have brain damage.

I was only six months old and I was supposed to croak during the surgery. And even if I somehow survived the mini-Hoover, I was supposed to suffer serious brain damage during the procedure and live the rest of my life as a vegetable.

Well, I obviously survived the surgery. I wouldn't be writing this if I didn't, but I have all sorts of physical problems that are directly the result of my brain damage.