Generalizability of nociception level as a measure of intraoperative nociceptive stimulation: A retrospective analysis.

BACKGROUND: Nociception-guided intraoperative opioid administration might help reduce postoperative pain. A commonly used and validated nociception monitor system is nociception level (NOL), which provides the nociception index, ranging from 0 to 100, with 0 representing no nociception and 100 representing extreme nociception. We tested the hypothesis that NOL responses are similar in men and women given remifentanil and fentanyl, across various types of anesthesia, as a function of American Society of Anesthesiologists physical status designations, and over a range of ages and body morphologies.

METHODS: We conducted a retrospective cohort analysis of trial data from eight prospective NOL validation studies. Among 522 noncardiac surgical patients enrolled in these studies, 447 were included in our analysis. We assessed NOL responses to various noxious and non-noxious stimuli.

RESULTS: The average NOL in response to 315 noxious stimuli was 47 ± 15 (95% CI = 45-49). The average NOL in response to 361 non-noxious stimuli was 10 ± 12 (95% CI = 9-11). NOL responses were similar in men and women, in patients given remifentanil and fentanyl, across various types of anesthesia, as a function of American Society of Anesthesiologists physical status designations, and over a range of ages and body morphologies.

CONCLUSION: Nociception level appears to provide accurate estimates of intraoperative nociception over a broad range of patients and anesthetic conditions.