 Levels of analgesia are traditionally evaluated by clinical signs such as an increase in heart rate, blood pressure, lacrimation, sweating and defensive movements. Recent research has been able to demonstrate the possibility of assessment of the level of nociception-antinociception balance by applying a tetanic stimulation 30 s, 60 milliampere, 50 Hz above the ulnar side of the wrist using a standard muscle relaxometer on the patients arm. In these investigations the stimulation led to a decrease of the vagal tonus resulting in changes in sinus arrhythmia and in a smaller area under the plethysmographic curve. Different devices were able to reflect a painful stimulus during propofol-remifentanil anesthesia. However, to the best of our knowledge, there are no data on the ability of the monitor-devices to detect a reproducible quantified painful stimulus under standardized conditions. 