The nociception level index (NOL) response to intubation and incision in patients undergoing video-assisted thoracoscopic surgery (VATS) with and without thoracic epidural analgesia. A pilot study. [version 1; referees: 3 approved, 1 approved with reservations]

Background: The PMD100™ (Medasense Biometrics Ltd., Ramat Yishai, Israel) is a novel non-invasive nociception monitor that integrates physiological parameters to compute a real-time nociception level index (NOL) in the anesthetized patients. Thoracic epidural analgesia provides effective analgesia and improves surgical outcomes. Side effects include sympathectomy, hypotension, changes in skin temperature and a decreased cardiac accelerator fiber tone. The purpose of this pilot study was to evaluate changes in NOL values after incision in patients with and without epidural analgesia. Methods: Half of the patients scheduled for Video-Assisted Thoracoscopic Surgery (VATS) received a thoracic epidural catheter, placed and tested 2h before surgery and activated prior to incision. The other half of the patients received i.v. fentanyl (1 mcg/kg) five minutes before incision. Anesthesia and analgesia were maintained in a standardized manner. NOL and heart rate (HR) were compared before and after the nociceptive stimuli intubation and skin incision. Results: NOL significantly increased in all patients after intubation by 10.2 points (CI: 4.5-16.0; p=0.002) as well as HR by 9 beats per minute after intubation in all patients (CI: 3.3-15.6; p=0.01). After incision, in patients without epidural analgesia the NOL increased by 13.9 points (CI: 7.4-20.3; p=0.0001), compared to 5.4 points (CI: -6.3-17.1; p=0.29) in patients with epidural analgesia. HR did not significantly vary after incision in both groups. The area under the curve of delta NOL and delta HR variations after incision were significantly different (p Conclusions: This pilot study suggests that the PMD100™ Monitor may be a useful tool to evaluate the efficacy of an intraoperative thoracic epidural analgesia. Clinical Trial Registry Number: ClinicalTrials.gov record ID: NCT01978379 registered 10/25/2014.