I've had countless panic attacks in the pastbut only one has ever made me faint (quite embarassing as I was in a pub at the time and I think people thought I was blind drunk!). So in answer to your question, yes, a panic attack can cause you to pass out but don't worry that it's going to happen all the time, it's probably just a one off. I read somewhere that if you do start to feel faint wiggling your toes around can help - putting your head between your knees also helps but you don't always want to be seen doing this, lol!
Sorry I've had no experience with gall bladder ops so can't help on that one, but I'm sure somebody else will.
.•:*¨¨*:•.Tracey.•:*¨¨*:•.
Fall seven times, stand up eight.
- Japanese proverb