Metabolized by the liver or kidneys. Important to hydrate before and after surgical procedures.

They are generally metabolized in the liver and excreted by the kidneys. Inhalational anesthetics are also mostly metabolized by the liver. Your anesthesia doctor would have reviewed your liver and kidney function tests before your procedure.

both by the kidney and the liver in general. your PCP should know if you are at risk for any specific or the anesthesiologist will see you prior to procedure.
generally safe, the shorter the procedure the better.