Medical Sciences have made advances in comprehending the highly complicated human body structure. The trend of new treatments keeps changing due to applying different sciences, and previously impossible things are now made possible. This is evident in the emergence of new surgical procedures in fixing tissues, which no one could even dream of and our surgeons' hands like a skilled artist have survived many lives by means of advanced medical equipment, and have increased individual's life expectancy. In addition to the surgeons, a successful surgery requires an appropriate anesthesia. Simply put, Anesthesiology is defined as lowering a patient's awareness of internal and external stimuli during an operation. The anesthesia is a difficult and complicated process since it is a journey from the edge of death to life; therefore, it is an anesthesiologist who is to recognize the thin line between the life and death to revive the patient after the surgery. Anesthesiology and intensive care are relatively new fields of science. The first successful anesthesia occurred in 1846, by a dentist, William Morton, who used ether in a public hospital in Massachusetts, the U.S. Since then, no new drug was found and no significant advance was made until 80 years later. The trend has recently undergone huge changes; new drug is being discovered every day and more precise care systems have been involved. After the discovery of anesthesia, great strides have been made toward the science and art of controlling pain, and providing the best conditions for resolving problems of surgical procedures, and facilitating the development of the science of surgery; that is definite to say: the world's modern surgery is indebted to the development of the science of Anesthesiology. The field of Anesthesiology used to be the sub-field of the surgery in the United States. It wasn't until 1941 when it was identified as an independent specialty among the others; since then thousands of individuals have succeeded in achieving board certifications from the U.S. universities. The training course provided in the United States and other countries, including Iran takes four years. After attaining an M.D. degree and passing the entrance exams, the candidates spend an additional 4 years completing a residency program, learning the aspects of clinical Anesthesiology and passing the related exams (licensing and board certification) to attain a degree in Anesthesiology. An anesthesiologist responsibility isn't merely limited to the operating rooms, but it involves providing services for the management of chronic and acute pains, intensive care units, cardiopulmonary resuscitation, pain clinics and toxicology units (acute and chronic intoxications).