druggies

Some things to consider
a) Heroin is ramped up morphine
b) I assume other analgesics have an abuse-able version. Not sure if people can really abuse derivatives of anaesthetics, but where there's a will there's a way.
c) Drug abuse increases the body's tolerance to that drug
d) Anaesthesiology seems like a pretty damn precise science

So as well as taking in age, sex, body mass, anaesthetists/anaesthesiologists also have to account for history of substance abuse.

And so when your liver/kidney is destroyed from ingesting all those drugs, you also have to worry about not being sedated enough as they cut you open. The joys of a life of drugs.


Also did you know anaesthetists (as they're called in British English, and perhaps it would be interesting to note that that is synonymous with English English) are over-represented in substance abuse, especially opioids?
-They have a much greater access to power drugs than the average joe. It is also relatively easy for them to nick a couple grams for personal use, compared to like, a street urchin.
-They spent years studying drugs so of course they would know how to use them properly, right?
-They see the effect of the highs on patients, the stimulation of reward centres, and think to themselves: "bucket listed".

This is all American data but nothing listed here seems culturally specific to the USA.