Hi there ~
I understand your concerns. The surgery itself would make you more susceptible to withdrawals especially so since general anesthesia
would be required to perform the surgery. I believe that you need to inform your doctor of the dependence issues with weed. If you continue to smoke and would have to quit cold
turkey due to the surgery, you may have withdrawal reactions and the symptoms should be treated, for which you need to let the surgeon and the anesthesia doctor know about the dependence. Using the vaporizer when you have enough consciousness after the surgery is what is usually advised, however your usage of marijuana is in itself lethal for surgical purposes if you do not let your doctors know about this issue.
I hope this helps. Take care and have a lovely day!