Inclusion Criteria:  Patients with elective trauma surgery and orthopedic surgery scheduled on a weekday Monday to Friday in the operation theater where the study is conducted  Exclusion Criteria:  Beta blocker, digitalis or cardiac pacemaker therapy Higher degrees of cardiac arrhythmias, e.g. atrial fibrillation and atrio-ventricular block >1st degree Severe peripheral or cardiac neuropathy Eye disease with affection of pupil reactivity Intraoperative treatment with ketamine, beta-receptor blockers, beta-receptor agonists or clonidine and treatment with vasoactive medication within 10 min before and during data acquisition period Inability to adequately specify postoperative pain level Postoperative care in the intensive care unit (ICU) or postanesthesia care unit with planned overnight stay (PACU24, intermediate care unit IMC)