During the current pain monitoring system the patient is awake and he/she is asked to give a numerical scale rating from 0 (no pain) to 10 (extreme pain). The purpose is to correlate the non-invasive measurements of the prototype device ANSPEC-PRO with these numbers to develop later a method/algorithm for automatic evaluation of pain (objective measurement of pain). The measurement is done using standard ECG electrodes placed in the hand palm of the patient. The patient feels nothing during the observations, perhaps irritation of skin may occur as result of long time measurement. As a comparison to the investigators prototype, a commercial device is also used in (randomly selected) patients, i.e. the MedStorm device.

The study will try to answer the following questions:

• Are the measurements with the ANSPEC-PRO correlated with the NRS values?
• What is the (mathematical) relationship between the measured values and the NRS?
• Is there difference between the two devices in measuring pain levels? And what is this difference if pain alleviation medication is given to the patient?
• A number of 26 patients is envisaged for this study, equally distributed to be evaluated with the two devices.

Inclusion Criteria:

• patients postoperative of a painfull operation
• between 18 and70 years old

Exclusion Criteria:

• day surgery patients
• chronic pain patients
• taken medication : anticonvulsants

Patients planned for operation, between 18 and 70 years old, not pregnant, not in chronic pain and not taken anticonvulsants or antidepressants.