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Ruetzler K, Montalvo M, Bakal O, Essber H, Rossler J, Mascha EJ, Han Y, Ramachandran M, Keebler A, Turan A, Sessler DI: Nociception level index-guided intraoperative analgesia for improved postoperative recovery: A randomized trial. Anesth Analg 2023

April 4, 2023

BACKGROUND:
Nociception is the physiological response to nociceptive stimuli, normally expe- rienced as pain. During general anesthesia, patients experience and respond to nociceptive stimuli by increasing blood pressure and heart rate if not controlled by preemptive analgesia. The PMD-200 system from Medasense (Ramat Gan, Israel) evaluates the balance between nociceptive stimuli and analgesia during general anesthesia and generates the nociception level (NOL) index from a single finger probe. NOL is a unitless index ranging from 0 to 100, with values exceeding 25 indicating that nociception exceeds analgesia. We aimed to demonstrate that titrating intraoperative opioid administration to keep NOL <25 optimizes intraoperative opioid dosing. Specifically, we tested the hypothesis that pain scores during the initial 60 min- utes of recovery are lower in patients managed with NOL-guided fentanyl than in patients given fentanyl per clinical routine. METHODS:
We conducted a randomized, single-center trial of patients having major abdominal open and laparoscopic surgeries. Patients were randomly assigned 1:1 to intraoperative NOL- guided fentanyl administration or fentanyl given per clinical routine. The primary outcome was pain score (0–10 verbal response scale) at 10-minute intervals during the initial 60 minutes of recovery. Our secondary outcome was a measure of adequate analgesia, defined as a pain score <5, assessed separately at each interval. RESULTS:
With a planned maximum sample size of 144, the study was stopped for futility after enrolling 72 patients from November 2020 to October 2021. Thirty-five patients were assigned to NOL-guided analgesic dosing and 37 to routine care. Patients in the NOL group spent sig- nificantly less time with a NOL index >25 (median reduction [95% confidence interval {CI}] of 14 [4–25] minutes) were given nearly twice as much intraoperative fentanyl (median [quartiles] 500 [330, 780] vs 300 [200, 330] μg), and required about half as much morphine in the recov- ery period (3.3 [0, 8] vs 7.7 [0, 13] mg). However, in the primary outcome analysis, NOL did not reduce pain scores in the first 60 minutes after awakening, assessed in a linear mixed effects model with mean (standard error [SE]) of 4.12 (0.59) for NOL and 4.04 (0.58) for routine care, and estimated difference in means of 0.08 (−1.43, 1.58), P = .895.
CONCLUSIONS:
More intraoperative fentanyl was given in NOL-guided patients, but NOL guid- ance did not reduce initial postoperative pain scores. (Anesth Analg 2023;136:761–71)