There are several reasons for drowsiness after surgery: First, before or during surgery, sedative drugs or general anesthetic drugs are used, and the drugs are not metabolized, so drowsiness can occur after surgery. Second, it is possible that the surgery is more traumatic and the person is more fatigued. Third, it is possible that the blood volume in the body is low due to excessive bleeding during surgery, resulting in low blood pressure and drowsiness. Fourth, attention must be paid to whether the stimulation of surgery has induced some conditions in the brain, commonly sudden cerebral infarction or cerebral hemorrhage, which leads to drowsiness in the brain function.