The body does respond with a surge. Adrenaline flows in that situation and it will cause a sharp rise. It is way more alarming for people to have a low bp after that. They are on their way to shock. Once you are beyond the adrenaline and not in pain, your pressure should return to it's own baseline. Sometimes the body will even try to protect itself by saving fluids. So, it doesn't make much urine. The extra fluids can raise the bp. Once the crisis is over, they run back and forth to the bathroom and get rid of the fluids after 24-48 hours. That is the body's frequent reaction to the stressor of surgery. Hope that is some reassurance. Hope your worst problem was your bp and not breaking your bones or others possibilities with trauma. Take care.
Pain will cause the BP to raise. I have a friend who is in severe pain constantly and her BP went up to 240/120 at one point. Needless to say, she went to the ER and is on BP medication. Under stress my BP will run around 160/100 when standing and dip to 139/89 when sitting. Since I'm always under stress, it's high. The doctors didn't seem too worried with these readings, although for me life style changes are in order. It sounds as if your situation should return to normal after the pain is under control. Always feel free to give your doc a call, just to set your mind at rest. You don't need additional worry while you are trying to heal. Have a speedy recovery and take care.