NOCICEPTION LEVEL INDEX-GUIDED ANALGESIA IN MAJOR SURGERY: A PROSPECTIVE OBSERVATIONAL STUDY

S. Notaro¹, E. Piscitelli¹, A. Imparato¹, P. Smaldone², S. Romano², L. Maresca³, A. Casalino³, L. Artefice¹, A. Notaro¹, M. Tamborino¹, C. Esposito¹ | ¹U.O.C. Anesthesia, Resuscitation and Intensive Care, Critical Care Department, “Vincenzo Monaldi” Hospital, AORN Azienda dei Colli, Napoli; ²U.O.C. Anesthesia, Resuscitation, University of Campania 'Luigi Vanvitelli', Napoli; ³U.O.C. Vascular Surgery, “Vincenzo Monaldi” Hospital, AORN Azienda dei Colli, Napoli

BACKGROUND
The accurate monitoring of intraoperative nociception remains a key objective in optimizing perioperative analgesia and minimizing opioid use. The Nociception Level (NOL) Index, a multiparametric indicator of nociceptive stress, offers real-time, objective data to guide analgesic strategies. This prospective observational study compares the efficacy of three regional analgesia techniques—Thoracic Epidural Analgesia (TEA), Erector Spinae Plane (ESP) block, and Transversus Abdominis Plane (TAP) block—administered using uniform protocols in patients undergoing vascular and general surgery.
METHODS
A prospective observational analysis was conducted on patients undergoing elective vascular (including open and endovascular thoracoabdominal procedures) and general surgery (open, laparoscopic, and robotic). Patients were allocated to receive TEA, ESP, or TAP block according to standard clinical protocols. To ensure intergroup comparability, regional blocks were administered using fixed and standardized doses: TEA with ropivacaine 0.2% (5–8 mL/h), ESP with 20 mL of ropivacaine 0.375%, and TAP with 20 mL ropivacaine 0.375% bilaterally. Volumes were selected independently of patient weight to ensure technique uniformity. These dosages were standardized within each technique based on current evidence and institutional protocols to ensure analgesic comparability while accounting for anatomical and pharmacokinetic differences. Fentanyl was administered in μg/kg according to predefined NOL-guided protocols. Intraoperative nociception was monitored using the NOL Index, and fentanyl administration followed predefined titration protocols based on NOL values. Postoperative analgesic consumption and adverse events were recorded.
RESULTS
A total of 189 patients were enrolled (TEA: n = 63; ESP: n = 61; TAP: n = 65). Mean age was 59 ± 13 years; 56% were female; ASA distribution was homogeneous among groups. Mean intraoperative fentanyl consumption was significantly lower in the TEA group (2.1 ± 0.4 μg/kg) compared to ESP (2.8 ± 0.5 μg/kg) and TAP (3.2 ± 0.6 μg/kg) (ANOVA, p < 0.001). Median NOL values were also significantly lower in the TEA group (median 18; IQR 15–24) versus ESP (25; IQR 20–33) and TAP (30; IQR 25–38) (ANOVA, p < 0.001). Hypotension was more frequent in the TEA group (28%) compared to ESP (12%) and TAP (9%) (Chi-square, p = 0.0004). Postoperative rescue analgesic requirement was significantly lower in the TEA group (ANOVA, p < 0.001).
CONCLUSIONS
TEA demonstrated superior control of intraoperative nociception and reduced opioid requirements, as well as lower postoperative analgesic needs. However, it was associated with a higher incidence of hypotension. The ESP block offered an effective compromise in high-risk patients, while the TAP block proved less efficacious in nociceptive control. The study supports the integration of NOL-guided analgesia protocols for real-time opioid titration and enhanced opioid-sparing strategies.