Color me skeptical about that double the amount of anesthesia stuff. Cannabis just doesn't have that level of effects, and it's not an antagonist against the drugs typically used in anesthesia. I know of no mechanism of action that could even begin to explain a 50% reduction of effect. It almost seems like doctors are equating narcotics abuse with cannabis and not segregating the two. A huge percentage of the people who abuse narcotics and other hard drugs also use cannabis. So if you ask them if they use narcotics the answer will most likely be a lie if they do, but they might be okay with telling the truth on the pot, especially now that it's legal in much of North America. So the end result is a very skewed, non-representative sample. Do a study where drug use history is determined by hair testing, not patient reporting, and we might learn the truth.
The trouble for doctors is it's been virtually impossible to do research on cannabis for the last 100 years (still is), and medical schools have never included it in their curriculums since it was outlawed (it was previously). And even as things loosen up today, there are few sources for them to learn about it, so they tend to operate on a lot of hearsay, articles in the popular press, and so forth.
