That is a perfectly sensible reason not to take nal. If you might need surgery at any moment, obviously you want to be prepared for surgery at any moment.
It's also a good reason not to drink, of course.

In fact, that was one of my motivations for moving faster towards getting a grip on my drinking -- I hope to have some elective surgery, and heavy drinkers are more likely to have surgery problems.
It has been about a month since you got the nal, though, so I can see why you're starting to wonder. Is there a time when you'll know for sure about the surgery?