Not frequent, but enough to make you question are we truly doing no harm when we indulge people. Medicine is an art, at the end of the day its a mix of statistics and experience. Not everything has a clear cut or even a right or wrong answer. Do this long enough, and you’ll see things that have minimal risk turn into a clusterfuck.

For your question, yes I’ve seen minor things end up killing someone through sheer bad luck things can spiral out of control despite all the right steps being taken. Hence the inherent risk they mention of death during all informed consents.