Guiding Opioid Administration by Nociception Level Index (NOL) in Patients With Regional Anesthesia

General anesthesia consists of a combination of hypnotic drugs to achieve unconsciousness and opioid analgesics to ensure antinociception. An alternative approach to the intraoperative administration of high-potency opioids to achieve antinociception during surgery is combining general anesthesia with regional anesthesia. Modern general anesthesia aims to avoid an overdose of opioid analgesics and reduce side effects of opioid administration. Quality and safety of general anesthesia are of major clinical importance and can be improved by adjusting the opioid analgesics to the optimal individual dose needed. In current clinical practice, opioid dosage is usually determined by clinical judgment. However, different monitoring devices estimating the effect of nociception during unconsciousness have become commercially available. One of the most recent commercially available nociception indices is the Nociception Level Index (NOL). Until today, there is conflicting evidence on whether guiding sufentanil administration by NOL monitoring, which is the intended use of the nociception index, affects postoperative pain level in the postanesthesia care unit (PACU), the amount of postoperatively administered opioids, and the quality of postoperative recovery in patients with a combination of general and regional anesthesia. This study aims to investigate the clinical performance of intraoperative NOL monitoring and determine whether guiding sufentanil administration by NOL monitoring - compared to routine care - reduces either postoperative pain level in the PACU, postoperative opioid consumption in the PACU or postoperative opioid consumption in the first 24 hours after the operation in patients having trauma and orthopedic surgery with combined general and regional anesthesia.