In recent years the growing interest in pain and its treatment has generated a greater number of studies for the assessment of these tools. The tools are basically regarded reliable but Grossman SA et al (5) have found that the intensity of pain expressed by patients on self-assessment scales correlates poorly with caregivers' assessments of pain, and the greater the intensity of the pain, the poorer the correlation between patient and caregiver. Moreover, patients, who can not communicate with the medical staff such as unconscious, or sedated patients, young pediatric patients or psychiatric or mentally retarded patients, are evaluated subjectively by the caregivers or the medical staff, this with wide variations which do not always assess correctly the pain status of the suffering patient. For this reason objective pain assessment tools have been suggested in recent past, for more accurate and comprehensive indication of this modality in patients in different settings including sedation and anesthesia.