I wouldn't risk it. Trying to time it right so you don't black out before the surgeons administer their drugs would be difficult to pull off. Since after all, you know what hospitals are like these days, they say they'll come get you in 20 mins time, but you could end up waiting for over an hour before they finally come to fetch you for the operation.
Really all you'd get out of it are some extra sedative drugs administered via injection. If you have access to dark web or access to benzos online, it's nothing too difficult you couldn't replicate with benzos. (Aren't most sedations just a mixture of benzos and opioids anyways?) I could only imagine someone resorting to this is if they were too broke to buy more benzos online.