They found that it only took four days of practicing a meditation technique called mindfulness meditation to change the pain responses in your brain. Brain activity decreased in areas devoted to monitoring a painful body part and also in areas responsible for relaying sensory information. This reduced the perception of pain by 57%.
Since the effect is so fast, if you have to go into the hospital for surgery, you might want to learn how to meditate at least four days ahead and start doing it twice a day. Oh, and you will want to continue meditating during your recovery.