Juniper Publishers - Journal of Anesthesia Introduction Measurement of anaesthetic depth is a challenging task for the anaesthesiologist. Ever since the first modern anaesthetics (ether, chloroform, and nitrous oxide) were used in the 1840, doctors have been searching for a reliable method of measuring the depth of the patient's unconsciousness. Research has indicated that patient's attitude towards undergoing surgery is affected by the possibility of awakening during the procedure. Post-traumatic stress disorder (PTSD) is a common result of awareness episodes. [ 1 , 2 ]. There are several reasons for anesthesiologist’s difficulty in evaluating dosages of anesthetic agents: The lack of a universally accepted definition of "consciousness". The complex effects of anesthesia on the human organism. The increased use of combinations of anesthetic agents rather than single drug. Changes in the patient's response to anesthesia over the course of
