Variations of nociception level (NOL®) measurements during robot-assisted laparoscopic prostatectomy - a monocentric retrospective analysis.

Background: Inadequate analgesia during anaesthesia is associated with a range of complications. While anaesthesiologists routinely monitor the depth of anaesthesia and neuromuscular blockade, no system currently in routine clinical use provides an objective assessment of adequacy of anti-nociception. Although various monitoring systems have been developed in recent years, their impact on the optimization of analgesic therapy remains uncertain. Moreover, the influence of perioperative surgical and non-surgical procedures and events on the measured parameters is not yet fully understood. Nonetheless, this knowledge is essential for the accurate interpretation and effective clinical application of these emerging monitoring technologies.

Methods: Thirty-three patients undergoing robot-assisted laparoscopic prostatectomy using the da Vinci Surgical System were retrospectively analysed. At five specific stimuli (gastric tube placement, urinary catheter placement, initiation of capnoperitoneum, transition to the steep Trendelenburg position and administration of sufentanil) NOL^®-Index, bispectral index (BIS™), heart rate and mean arterial blood pressure were measured after one, three and five minutes.

Results: We noticed a significant increase in NOL^®-Index with capnoperitoneum (Beta 14.22, p < 0.001), while the NOL^®-Index decreased after steep Trendelenburg position (Beta - 8.89, p = 0.002) and sufentanil application (Beta - 17.67, p < 0.001). No significant changes were observed during gastric tube placement and urinary catheter insertion. The BIS^™ analysis showed no relevant deviation during anaesthesia.

Conclusion: The NOL^®-Index showed characteristic changes during robot-assisted laparoscopic prostatectomy. Our study shows plausible results that can be used as a basis for future prospective studies to evaluate the clinical relevance of nociceptive monitoring.