The anesthesiologist fulfills several critical roles in the perioperative period apart from the actual administration of the anesthetic. The anesthesiologist functions also as a “primary care” physician for the patient’s medical conditions in the operating room. Anesthesiologists have a wide range of core medical knowledge as well as broad experience in managing coexisting disease in the operating room. They also have specialty knowledge in cardiovascular and respiratory physiology, and critical event management. Many issues of interest to the anesthesiologist in the perioperative period overlap with concerns of the medicine consultant.