An anesthesiologist is a physician who has completed medical or osteopathic school, completed an internship in medicine, surgery, pediatrics, or a combination of these, and has undertaken three additional years of residency training in anesthesiology. Some anesthesiologists complete an additional year or two of fellowship training to sub-specialize in specific areas of practice, including: pediatric anesthesia, pain medicine, obstetric anesthesia, neuroanesthesia, cardiovascular anesthesia, and critical care medicine. After completion of training, anesthesiologists often practice in varied settings. Most focus on the perioperative care of patients, offering expertise in the medical evaluation, preoperative preparation, intraoperative medical managment, and postoperative care of critically ill patients. In addition to the perioperative medical care of surgical patients, some anesthesiologists specialize in the treatment of postoperative pain, chronic pain conditions, obstetric labor pain, and cancer pain. Others may provide medical care as critical care (intensive care unit) medicine specialists.